{"product_id":"axial-spondyloarthritis-understanding-the-challenges-doctors-face-in-making-the-diagnosis","title":"Axial Spondyloarthritis: Understanding the Challenges Doctors Face in Making the Diagnosis","description":"\u003cp\u003eAxial spondyloarthritis (axSpA) is a chronic inflammatory joint disease that mainly affects the spine and the sacroiliac (SI) joints, and its diagnosis can be challenging because no single test, symptom, or imaging finding can confirm or rule it out on its own. A new review article explains that diagnosis relies on recognizing a pattern of clinical, laboratory, and imaging features, while carefully excluding other causes of back pain. The authors highlight three common pitfalls in practice: using research classification criteria as if they were diagnostic tests, simply counting disease features without clinical reasoning, and over-relying on imaging results. This patient-friendly article translates the full paper, including all statistics and study data, and explains what the findings mean for people living with back pain and suspected axSpA.\u003c\/p\u003e\n\n\u003ch1\u003eAxial Spondyloarthritis: Understanding the Challenges Doctors Face in Making the Diagnosis\u003c\/h1\u003e\n\n\u003ch2\u003eTable of Contents\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"#ddn-key-points\"\u003eKey Points\u003c\/a\u003e\u003c\/li\u003e\n\n  \u003cli\u003e\u003ca href=\"#background\"\u003eBackground: What Is Axial Spondyloarthritis?\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#principles\"\u003eGeneral Principles of Diagnosis: Why It Is So Difficult\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#age\"\u003eBuilding Block 1: Age When Back Pain Starts\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#history\"\u003eBuilding Block 2: Patient History and Physical Examination\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#lab\"\u003eBuilding Block 3: Laboratory Testing (CRP and HLA-B27)\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#imaging\"\u003eBuilding Block 4: Imaging Studies (X-Rays and MRI)\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#differential\"\u003eDifferential Diagnosis: Other Conditions That Mimic axSpA\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#approach\"\u003eThe Usual Approach to Diagnosing axSpA and How Doctors Build Their Skills\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#pitfall1\"\u003ePitfall 1: Using Classification Criteria as Diagnostic Criteria\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#pitfall2\"\u003ePitfall 2: Diagnosing by Simply Counting SpA Features\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#pitfall3\"\u003ePitfall 3: Over-Reliance on Imaging Findings\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#final\"\u003eFinal Thoughts and What To Do if the Diagnosis Is Unclear\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#practice\"\u003ePractice Points for Doctors (and What Patients Should Know)\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#ddn-faq\"\u003eFrequently Asked Questions\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"#source\"\u003eSource Information\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c!-- ddn:keypoints:start --\u003e\n\u003ch2 id=\"ddn-key-points\"\u003eKey Points\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eNo single test, symptom, or imaging finding can confirm or rule out axial spondyloarthritis by itself.\u003c\/li\u003e\n\u003cli\u003eIn a worldwide study of 2,579 patients, 92% developed axial symptoms before age 45.\u003c\/li\u003e\n\u003cli\u003eUsing research classification criteria as diagnostic tests is a common pitfall and misclassifies many patients.\u003c\/li\u003e\n\u003cli\u003eCounting SpA features is insufficient; even with four or more features, about 15% of patients did not have axial spondyloarthritis.\u003c\/li\u003e\n\u003cli\u003eMRI bone marrow edema also occurs in healthy people, runners, and postpartum women, so imaging must be interpreted with clinical context.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- ddn:keypoints:end --\u003e\n\n\n\u003ch2 id=\"background\"\u003eBackground: What Is Axial Spondyloarthritis?\u003c\/h2\u003e\n\n\u003cp\u003eAxial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease (a type of autoimmune-related condition that causes joint inflammation). It mainly affects the spine and the sacroiliac (SI) joints — the joints connecting the lower spine to the pelvis. Inflammation in these areas causes back pain and stiffness.\u003c\/p\u003e\n\n\u003cp\u003eBeyond the spine, other symptoms are common. Peripheral manifestations affect the limbs and include arthritis (joint inflammation in the arms or legs), enthesitis (inflammation where tendons or ligaments attach to bone), and dactylitis (whole-finger or whole-toe swelling, sometimes called \"sausage digit\"). Extra-musculoskeletal manifestations (EMMs) affect other body systems and include inflammatory bowel disease (IBD, chronic inflammation of the digestive tract), psoriasis (PSO, a skin condition with scaly patches), and anterior uveitis (AU, inflammation inside the eye). Together, these features contribute to the overall burden of axSpA.\u003c\/p\u003e\n\n\u003cp\u003eAxSpA is divided into two subtypes:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNon-radiographic axSpA (nr-axSpA):\u003c\/strong\u003e Patients have symptoms but no definite signs of sacroiliitis (SI joint inflammation) visible on conventional X-rays.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRadiographic axSpA (r-axSpA):\u003c\/strong\u003e Previously called ankylosing spondylitis (AS). These patients do have definite sacroiliitis visible on conventional X-rays.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor the most part, the clinical presentation and management of the two forms are very similar. One exception matters: some r-axSpA patients have extensive spinal damage. For them, preventing progressive spinal damage — and occasionally surgically correcting spinal deformity — becomes an important part of care.\u003c\/p\u003e\n\n\u003cp\u003eThe nr-axSpA versus r-axSpA distinction is still clinically important for two reasons. First, regulatory agencies like the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) require clinical trials to be performed in \u003cem\u003eboth\u003c\/em\u003e disease forms before approving new pharmaceutical treatments. Second, the rate of spinal damage progression differs: damage mainly develops in patients with r-axSpA, not nr-axSpA.\u003c\/p\u003e\n\n\u003ch2 id=\"principles\"\u003eGeneral Principles of Diagnosis: Why It Is So Difficult\u003c\/h2\u003e\n\n\u003cp\u003eaxSpA has a highly varied (heterogeneous) presentation. No single feature from a patient's history, physical examination, laboratory testing, or imaging studies has enough sensitivity and specificity to diagnose — or exclude — axSpA on its own.\u003c\/p\u003e\n\n\u003cp\u003eSensitivity means how well a test catches people who truly have the disease. Specificity means how well it rules out people who do not. For axSpA, every feature falls short on at least one of these measures when used alone.\u003c\/p\u003e\n\n\u003cp\u003eBecause back pain is usually the main complaint that triggers a diagnostic workup, diagnosis involves two mental tasks happening at once. The doctor must recognize a \u003cem\u003epattern\u003c\/em\u003e of features that, taken together, provides enough evidence to diagnose the disease. At the same time, the doctor must exclude \u003cem\u003eother potential causes\u003c\/em\u003e of back pain — called the differential diagnosis.\u003c\/p\u003e\n\n\u003ch2 id=\"age\"\u003eBuilding Block 1: Age When Back Pain Starts\u003c\/h2\u003e\n\n\u003cp\u003eaxSpA usually begins in the second or third decade of life — meaning the teens, twenties, and thirties. Starting after age 45 is uncommon. That makes the age at onset of the first back pain symptoms a very useful, easy, and accessible piece of information for the first selection of patients with chronic back pain.\u003c\/p\u003e\n\n\u003cp\u003eMost evidence originally came from European studies. A recent international study confirms the same pattern worldwide. The Assessment of SpondyloArthritis international Society (ASAS)-PerSpA study included \u003cstrong\u003e2,579 axSpA patients\u003c\/strong\u003e, and \u003cstrong\u003e92%\u003c\/strong\u003e had developed axial symptoms (spine-related symptoms) before age 45.\u003c\/p\u003e\n\n\u003cp\u003eStrikingly, the results varied little across geographical regions:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAsia:\u003c\/strong\u003e 574 patients, 94% had symptom onset before age 45\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eEurope and North America:\u003c\/strong\u003e 998 patients, 92%\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLatin America:\u003c\/strong\u003e 246 patients, 89%\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMiddle East and North Africa:\u003c\/strong\u003e 771 patients, 91%\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe study also confirmed earlier findings about who tends to develop symptoms earlier. Age at onset of axial symptoms was consistently lower in \u003cstrong\u003eHLA-B27-positive patients\u003c\/strong\u003e (people carrying the main genetic risk factor for axSpA) — a median of 25 years (IQR 19–32) versus 31 years (IQR 22–39) in HLA-B27-negative patients. Men also tended to develop symptoms earlier than women: a median of 25 years (IQR 19–33) versus 28 years (IQR 21–37).\u003c\/p\u003e\n\n\u003cp\u003eHowever, after statistical adjustment (multivariable models), an independent effect of male gender beyond HLA-B27 was only found in Asian patients. The bottom line for patients: around the world, the vast majority of people with axSpA develop back pain before age 45. Back pain that starts well after 45 is unlikely to be axSpA.\u003c\/p\u003e\n\n\u003ch2 id=\"history\"\u003eBuilding Block 2: Patient History and Physical Examination\u003c\/h2\u003e\n\n\u003cp\u003eThe medical history of any back pain patient suspected of having axSpA should always cover the duration and characteristics of the pain. In particular, doctors look for features suggesting an \u003cstrong\u003einflammatory\u003c\/strong\u003e cause. Inflammatory back pain differs from mechanical back pain: it tends to be worse at rest, improves with exercise, and often wakes people in the second half of the night.\u003c\/p\u003e\n\n\u003cp\u003eSeveral sets of questions have been published over time, aiming to identify a history suggestive of inflammatory back pain (IBP). The most recent and widely used are the \u003cstrong\u003eASAS expert criteria for IBP\u003c\/strong\u003e. A patient is classified as having IBP if at least 4 out of these 5 features are present:\u003c\/p\u003e\n\u003col\u003e\n  \u003cli\u003eAge at onset under 40 years\u003c\/li\u003e\n  \u003cli\u003eInsidious (gradual) onset rather than sudden\u003c\/li\u003e\n  \u003cli\u003eImprovement with exercise\u003c\/li\u003e\n  \u003cli\u003eNo improvement with rest\u003c\/li\u003e\n  \u003cli\u003ePain at night (with improvement upon getting up)\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003cp\u003eIn the original publication validating these criteria, the presence of 4 of the 5 features had a sensitivity of 80% and a specificity of 74%, using overall expert judgment on IBP as the gold standard. In plain terms: 80% of people judged by experts to have IBP were correctly identified by the criteria, and 74% of people without IBP were correctly excluded.\u003c\/p\u003e\n\n\u003cp\u003eBecause the questions are easy to apply, IBP is commonly used in referral recommendations directing patients with back pain to rheumatologists. As a result, IBP is very common among the patients who actually arrive in a rheumatologist's office. The downside: several publications have reported a reduced discriminative value of IBP in that setting. In other words, once you are already seeing a rheumatologist because your doctor suspected axSpA, \"Do you have inflammatory back pain?\" is a less powerful question than it was for selecting patients in the first place.\u003c\/p\u003e\n\n\u003cp\u003eA thorough history also covers other SpA features. The doctor will ask about:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eCurrent or past arthritis (joint inflammation), enthesitis, or dactylitis\u003c\/li\u003e\n  \u003cli\u003ePsoriasis, inflammatory bowel disease, and acute anterior uveitis\u003c\/li\u003e\n  \u003cli\u003eFamily history of SpA, including uveitis and axSpA in family members\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eResponse to nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen, naproxen, or diclofenac) is also informative. Although back pain of many causes may improve with NSAIDs, marked improvement in pain within one or two days of starting NSAIDs supports an axSpA diagnosis.\u003c\/p\u003e\n\n\u003cp\u003eHistory taking must also pursue the \u003cem\u003ealternative\u003c\/em\u003e explanations for back pain. Doctors should ask about previous episodes of back pain or injury, back surgery, weight loss and fever, neurological symptoms (like numbness or weakness), and widespread pain.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003ePhysical examination\u003c\/strong\u003e is an important part of the diagnostic workup. It usually includes:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eExamining the joints for arthritis\u003c\/li\u003e\n  \u003cli\u003eExamining the heels for enthesitis of the Achilles tendon\u003c\/li\u003e\n  \u003cli\u003eChecking the hands and feet for dactylitis\u003c\/li\u003e\n  \u003cli\u003eChecking the nails and skin for psoriasis\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eSigns of active acute uveitis are not commonly detected by rheumatologists in patients with back pain, but when present they greatly increase the likelihood of axSpA.\u003c\/p\u003e\n\n\u003cp\u003eDoctors can measure spinal mobility restriction in several ways. Commonly used measures include cervical rotation (how far you can turn your head), chest expansion (to measure the range of motion of the costovertebral joints), the Schober test (range of motion of the lower spine in the sagittal plane, i.e., bending forward), and lateral spinal flexion (bending sideways). Age-stratified reference intervals for various spinal mobility measurements in Europeans have been published and are freely available through the ASAS website (https:\/\/www.asas-group.org\/instruments\/mobility-curves\/).\u003c\/p\u003e\n\n\u003cp\u003eUnfortunately, spinal mobility tests have limited diagnostic value. Spinal mobility varies greatly among normal individuals and decreases with advancing age. Also, in a cohort of chronic back pain patients suspected of having early axSpA — the SPACE cohort, discussed further below — impaired spinal mobility occurred just as often in patients with early axSpA as in patients with other forms of chronic back pain.\u003c\/p\u003e\n\n\u003ch2 id=\"lab\"\u003eBuilding Block 3: Laboratory Testing (CRP and HLA-B27)\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eC-reactive protein (CRP)\u003c\/strong\u003e, a marker of inflammation produced by the liver, should be measured in patients suspected of having axSpA. Elevated CRP levels are seen in only about \u003cstrong\u003e25–40%\u003c\/strong\u003e of patients with axSpA. This means the majority of axSpA patients have a normal CRP — so a normal level definitely does not rule out the disease.\u003c\/p\u003e\n\n\u003cp\u003eCRP levels also serve another function beyond diagnosis. They are part of the ASDAS (Axial Spondyloarthritis Disease Activity Score), a composite measure of disease activity preferred for axSpA. Over time, elevated CRP is associated with spinal radiographic progression — meaning visible damage on X-rays. When CRP testing is unavailable, the erythrocyte sedimentation rate (ESR, another inflammation blood test) is an alternative. An elevated CRP or ESR could also be caused by something entirely unrelated to axSpA.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHLA-B27\u003c\/strong\u003e (human leukocyte antigen B27) is a genetic marker and by far the most important single genetic risk factor for axSpA. axSpA is a complex polygenic disease, meaning many genes contribute, but HLA-B27 dominates. Worldwide, HLA-B27 prevalence varies enormously between populations: less than 1% in some Sub-Saharan African studies, up to over 30% in Northern Arctic communities such as the Chukchi and Inuit. The prevalence of HLA-B27 in a given population mirrors the prevalence of axSpA there, underscoring its importance in disease development.\u003c\/p\u003e\n\n\u003cp\u003eThe diagnostic value of HLA-B27 testing comes from the fact that HLA-B27 is consistently far more common in axSpA patients than in the general population. In the ASAS-PerSpA study mentioned earlier:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e89%\u003c\/strong\u003e of axSpA patients from Asia were HLA-B27 positive\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e65%\u003c\/strong\u003e from the Middle East and North Africa\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e81%\u003c\/strong\u003e from Latin America\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e78%\u003c\/strong\u003e from Europe and North America\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor reference, only about \u003cstrong\u003e6–8%\u003c\/strong\u003e of the general population in Europe and North America carries HLA-B27. So a positive test meaningfully shifts the probability, although it is not a diagnosis by itself — and many HLA-B27-positive people never develop axSpA.\u003c\/p\u003e\n\n\u003ch2 id=\"imaging\"\u003eBuilding Block 4: Imaging Studies (X-Rays and MRI)\u003c\/h2\u003e\n\n\u003cp\u003eImaging plays an important role in diagnosing axSpA. Inflammation may occur throughout the entire spine, but it is easiest to detect in the sacroiliac (SI) joints — the joints where the spine meets the pelvis. At many centers, a plain radiograph (X-ray) of the pelvis remains the first imaging study, because it can show sacroiliitis and is less expensive and resource-intensive than MRI (magnetic resonance imaging).\u003c\/p\u003e\n\n\u003cp\u003eOn radiographs, the right and left SI joints are graded separately according to how much damage is visible. The grading scale is:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGrade 0:\u003c\/strong\u003e Normal\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGrade 1:\u003c\/strong\u003e Suspicious changes\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGrade 2:\u003c\/strong\u003e Minimal abnormality — small localized areas with erosions or sclerosis (hardening of bone), without alteration in joint width\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGrade 3:\u003c\/strong\u003e Unequivocal abnormality — moderate or advanced sacroiliitis with one or more of the following: erosions, sclerosis, joint space widening, narrowing, or partial ankylosis (fusion)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGrade 4:\u003c\/strong\u003e Total ankylosis (complete fusion of the joint)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eAccording to this grading system, a radiograph counts as positive for sacroiliitis if the score is \u003cstrong\u003egrade 2 or higher on both sides (bilaterally)\u003c\/strong\u003e, or \u003cstrong\u003egrade 3 or higher on one side (unilaterally)\u003c\/strong\u003e. Examples of radiographs at different grades are available in the ASAS slide library under \"X-ray\" (www.asas-group.org\/education\/asas-slide-library\/).\u003c\/p\u003e\n\n\u003cp\u003eHowever, X-rays have serious limitations for early disease. Patients may have symptoms from sacroiliitis for several years before any abnormality becomes visible on radiography. Emerging data also suggest that the transition from non-radiographic to radiographic axSpA is a slow process, and many nr-axSpA patients may never develop visible X-ray abnormalities at all. Furthermore, interpreting SI joint X-rays is not always easy: interobserver and intra-observer variation is substantial, meaning sacroiliitis can be missed or wrongly assumed to be present.\u003c\/p\u003e\n\n\u003cp\u003eIn patients who already have obvious sacroiliitis on X-ray, additional imaging such as MRI may not be necessary for diagnosis. But \u003cstrong\u003eMRI is capable of detecting inflammation in the SI joints before any change appears on X-ray\u003c\/strong\u003e. Unlike plain radiographs, MRI can reveal inflammatory changes (such as bone marrow edema — essentially fluid and inflammation inside the bone), fatty changes, and more subtle structural abnormalities. MRI also shows better interreader reliability than conventional radiography, meaning different doctors reading the same scan are more likely to agree.\u003c\/p\u003e\n\n\u003cp\u003eFor patients whose initial MRI of the SI joints is negative (no sacroiliitis visible), a follow-up MRI can generally be considered when axSpA is still suspected. But the chance that a negative MRI becomes positive at follow-up after 3–12 months is very low — particularly for women (\u003cstrong\u003e2.8%\u003c\/strong\u003e) and for HLA-B27-negative patients (\u003cstrong\u003e1.5%\u003c\/strong\u003e). The conversion rate is somewhat higher for men (\u003cstrong\u003e12%\u003c\/strong\u003e) and for HLA-B27-positive patients (\u003cstrong\u003e11%\u003c\/strong\u003e).\u003c\/p\u003e\n\n\u003cp\u003eRoutine MRI or radiography of the spine is \u003cem\u003enot\u003c\/em\u003e standard in the diagnosis of axSpA. However, it can be very useful when a doctor suspects a condition other than SpA, or to actively rule out other causes of back pain.\u003c\/p\u003e\n\n\u003ch2 id=\"differential\"\u003eDifferential Diagnosis: Other Conditions That Mimic axSpA\u003c\/h2\u003e\n\n\u003cp\u003eMany conditions that cause chronic spinal and low back pain can look like axSpA. In the \u003cstrong\u003eSpondyloarthritis Caught Early (SPACE) cohort\u003c\/strong\u003e — a study of chronic back pain patients referred to a rheumatologist, with back pain onset before age 45 and symptom duration under two years — the common diagnoses in patients who did \u003cem\u003enot\u003c\/em\u003e have axSpA were:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eNon-specific back pain\u003c\/li\u003e\n  \u003cli\u003eMechanical back pain\u003c\/li\u003e\n  \u003cli\u003eInflammatory back pain without SpA\u003c\/li\u003e\n  \u003cli\u003eDegenerative disc disease\u003c\/li\u003e\n  \u003cli\u003e(Fibro)myalgia\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eIt is important to remember that those chronic back pain patients were young adults with a mean age under 30 years. In other groups of chronic back pain patients — especially older patients — other causes become more likely. Those include osteoporotic fractures (fractures from weakened bone), osteoarthritis of the spine, malignancy (cancer), and diffuse idiopathic skeletal hyperostosis (DISH, a condition with abnormal bone growth along the spine).\u003c\/p\u003e\n\n\u003ch2 id=\"approach\"\u003eThe Usual Approach to Diagnosing axSpA and How Doctors Build Their Skills\u003c\/h2\u003e\n\n\u003cp\u003eHaving a mental picture of a typical disease presentation helps with identification and workup. The authors, who practice in Western Europe, describe a typical axSpA patient this way: a young adult with chronic inflammatory back pain (or at least several features associated with IBP) located in the lower back, starting before age 40 to 50, usually HLA-B27 positive, with one or two other SpA features, and clear signs of sacroiliitis on imaging.\u003c\/p\u003e\n\n\u003cp\u003eBut the authors stress that axSpA is heterogeneous — many patients do not follow this typical picture. One rule guides their practice: they are very reluctant to diagnose axSpA if no signs of active inflammation or post-inflammatory structural lesions can be found in the SI joints or the spine.\u003c\/p\u003e\n\n\u003cp\u003eTo build diagnostic skills, the authors strongly recommend training in three areas: assessing clinical signs of SpA, recognizing patterns, and interpreting images. Educational initiatives are underway worldwide. One free resource is the \u003cstrong\u003eASAS interactive online case library\u003c\/strong\u003e (www.asas-group.org\/education\/asas-case-library), which contains over 30 clinical cases spanning the full spectrum of axSpA and the most common differential diagnoses. Each case discusses imaging in the context of clinical findings and laboratory results.\u003c\/p\u003e\n\n\u003cp\u003eThe authors then present the three pitfalls they encounter most commonly in clinical practice.\u003c\/p\u003e\n\n\u003ch2 id=\"pitfall1\"\u003ePitfall 1: Using Classification Criteria as Diagnostic Criteria\u003c\/h2\u003e\n\n\u003cp\u003eClassification criteria for axSpA exist, but they serve a research purpose, not a patient-care purpose. These criteria are standardized definitions designed to create well-defined, relatively homogeneous groups of patients for clinical and laboratory research. The current version is the \u003cstrong\u003e2009 ASAS classification criteria for axSpA\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cp\u003eTo be \u003cem\u003eclassified\u003c\/em\u003e as having axSpA for a research study, a patient must fulfill the entry criterion: chronic back pain lasting more than three months, starting before age 45. Then, one of two pathways must be satisfied:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eImaging pathway:\u003c\/strong\u003e Sacroiliitis on imaging (active inflammation on MRI highly suggestive of SpA, OR definite radiographic sacroiliitis per the modified New York criteria) PLUS at least one other SpA feature.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHLA-B27 pathway:\u003c\/strong\u003e HLA-B27 positive PLUS at least two other SpA features.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe other SpA features listed in the 2009 ASAS criteria include all the items discussed in this article: inflammatory back pain, arthritis, enthesitis (heel), dactylitis, psoriasis, inflammatory bowel disease, acute anterior uveitis, good response to NSAIDs, and family history of SpA.\u003c\/p\u003e\n\n\u003cp\u003eAt first glance, these criteria look easy to use for diagnosis too. They are not. Using classification criteria as diagnostic criteria creates two problems. First, it ignores the crucial issue of differential diagnosis — a feature list does not consider whether something else better explains the symptoms. Second, it produces an unacceptable number of misdiagnoses in both directions: axSpA patients incorrectly not diagnosed (because the criteria have too low sensitivity for diagnosis), and patients without axSpA incorrectly labeled as having it (because the criteria have too low specificity for diagnosis).\u003c\/p\u003e\n\n\u003cp\u003eThese limitations stem, in part, from the categorical nature of classification criteria — a patient either fulfills them or does not. Real clinical diagnosis, by contrast, allows flexibility and encompasses a broad spectrum of diagnostic confidence.\u003c\/p\u003e\n\n\u003cp\u003eThe numbers confirm the problem. In a meta-analysis of \u003cstrong\u003e4,990 patients from seven studies\u003c\/strong\u003e, the sensitivity of the ASAS axSpA classification criteria was \u003cstrong\u003e82%\u003c\/strong\u003e (95% confidence interval 77–96%), and the specificity was \u003cstrong\u003e87%\u003c\/strong\u003e (95% confidence interval 78–92%). A test that misses roughly 18 out of every 100 true cases, and falsely labels about 13 out of every 100 non-cases, is not an acceptable diagnostic tool on its own.\u003c\/p\u003e\n\n\u003ch2 id=\"pitfall2\"\u003ePitfall 2: Diagnosing by Simply Counting SpA Features\u003c\/h2\u003e\n\n\u003cp\u003eIn a patient with chronic back pain, each additional SpA feature increases the chance that the pain is caused by axSpA. Every feature carries some diagnostic weight, and multiple features make axSpA progressively more likely. To help doctors, a formal diagnostic algorithm exists. The \u003cstrong\u003eASAS-modified Berlin algorithm\u003c\/strong\u003e suggests that a patient with chronic back pain who has \u003cstrong\u003e4 or more SpA features\u003c\/strong\u003e can be diagnosed with axSpA without further imaging or HLA-B27 testing.\u003c\/p\u003e\n\n\u003cp\u003eThe authors stress that this algorithm is only a decision aid for rheumatologists. It cannot and should not replace a proper differential diagnostic assessment in patients with chronic back pain.\u003c\/p\u003e\n\n\u003cp\u003eThe reason: SpA features are extremely diverse. They range from genetic risk (HLA-B27), to inflammation in the peripheral skeleton (arthritis), to inflammation in the axial skeleton (sacroiliitis on MRI), to inflammation outside the joints (psoriasis). The features must be combined into a \u003cem\u003emeaningful pattern\u003c\/em\u003e that points toward inflammation in the axial skeleton.\u003c\/p\u003e\n\n\u003cp\u003eConsider this example from the article: a patient with \u003cem\u003eperipheral\u003c\/em\u003e spondyloarthritis has psoriasis, arthritis, and dactylitis — already three SpA features. If that patient develops chronic back pain, the pain does not automatically mean axSpA. The three existing features raise suspicion, but the back pain could easily have an entirely different mechanical cause.\u003c\/p\u003e\n\n\u003cp\u003eThe SPACE cohort quantified this issue. In \u003cstrong\u003e500 patients\u003c\/strong\u003e suspected of having axSpA, a diagnosis was eventually made in \u003cstrong\u003e250 patients (50%)\u003c\/strong\u003e. The rate of confirmed axSpA rose steadily with the number of SpA features:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e1 or fewer\u003c\/strong\u003e SpA features: axSpA in \u003cstrong\u003e24%\u003c\/strong\u003e of patients\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e2\u003c\/strong\u003e SpA features: \u003cstrong\u003e43%\u003c\/strong\u003e\n\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e3\u003c\/strong\u003e SpA features: \u003cstrong\u003e62%\u003c\/strong\u003e\n\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e4 or more\u003c\/strong\u003e SpA features: \u003cstrong\u003e85%\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThis shows two things. More features indeed make axSpA more likely. But it also shows that even numerous SpA features do not automatically produce an axSpA diagnosis: \u003cstrong\u003e15%\u003c\/strong\u003e of patients with four or more features (about 1 in 7) turned out \u003cem\u003enot\u003c\/em\u003e to have axSpA. Counting alone is therefore insufficient. Clinical reasoning about alternative explanations remains essential.\u003c\/p\u003e\n\n\u003ch2 id=\"pitfall3\"\u003ePitfall 3: Over-Reliance on Imaging Findings\u003c\/h2\u003e\n\n\u003cp\u003eImaging — whether X-ray or MRI — detects inflammation or post-inflammatory changes in the spine and SI joints, and it plays a very important role in diagnosing axSpA. Over-reliance on imaging, however, leads to misdiagnosis.\u003c\/p\u003e\n\n\u003cp\u003eX-rays of the SI joints cannot detect axSpA when structural damage has not yet occurred, and they suffer from substantial intra- and inter-reader variability (the same reader, or different readers, may grade the same image differently). MRI is therefore increasingly used to visualize inflammation in the SI joints. MRI can detect various lesions associated with axSpA, but \u003cstrong\u003ebone marrow edema (BME)\u003c\/strong\u003e — visible as bright spots indicating active inflammation inside the bone — has been, and still is, considered the most diagnostically useful finding.\u003c\/p\u003e\n\n\u003cp\u003eThe MRI definition of sacroiliitis has evolved. In the first definition in 2009, only BME reflecting active sacroiliitis counted as a relevant lesion. Knowledge of structural lesions on MRI has grown since then. The revised \u003cstrong\u003e2016 ASAS definition\u003c\/strong\u003e still centers on detecting BME typical of SpA, but it now acknowledges the additional diagnostic value of concomitant structural lesions — such as erosions (bone surface damage), bony ankylosis (fusion), and fat metaplasia (fatty changes in bone marrow). These structural lesions matter most when BME findings are doubtful; they can increase diagnostic confidence.\u003c\/p\u003e\n\n\u003cp\u003eThe usefulness of MRI is limited by two factors. First, interpreting these images is difficult, especially without special training. Second, MRI must be interpreted in the context of the degree of clinical suspicion — an MRI finding means something different in a patient with high clinical probability than in a patient with low probability.\u003c\/p\u003e\n\n\u003cp\u003eOther causes of BME in the SI joints, especially mechanical stress, must always be considered. Multiple studies have reported SI joint BME in people \u003cem\u003ewithout\u003c\/em\u003e axSpA:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eIn \u003cstrong\u003e47 Dutch healthy volunteers\u003c\/strong\u003e, \u003cstrong\u003e23%\u003c\/strong\u003e had an MRI \"positive for sacroiliitis,\" compared with \u003cstrong\u003e92%\u003c\/strong\u003e of 47 axSpA patients and only \u003cstrong\u003e6%\u003c\/strong\u003e of 47 patients with chronic back pain.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e13%\u003c\/strong\u003e of 24 runners had a \"positive MRI.\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e57%\u003c\/strong\u003e of 7 women with postpartum (after childbirth) low back pain had a \"positive MRI.\"\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eNone of the BME findings in the people \u003cem\u003ewithout\u003c\/em\u003e axSpA included deep lesions (defined as a homogeneous signal extending at least 1 cm from the joint surface). And the more SI joint quadrants or MRI slices showing BME, the higher the likelihood that the lesion was due to axSpA.\u003c\/p\u003e\n\n\u003cp\u003eA Danish study found that in recreational runners and elite ice-hockey players, \u003cstrong\u003e30–41%\u003c\/strong\u003e had BME that fulfilled the ASAS definition, with the posterior lower ilium as the most frequently affected quadrant. Erosions were virtually absent in these healthy athletes.\u003c\/p\u003e\n\n\u003cp\u003eThe takeaway: just like sacroiliitis on X-rays, MRI findings of BME alone are not necessarily diagnostic of axSpA. MRI must always be interpreted in the context of clinical and laboratory findings.\u003c\/p\u003e\n\n\u003ch2 id=\"final\"\u003eFinal Thoughts and What To Do if the Diagnosis Is Unclear\u003c\/h2\u003e\n\n\u003cp\u003ePharmaceutical treatment options for axSpA are rapidly increasing. Key goals of management are to control symptoms, restore function and quality of life, and slow disease progression. Obviously, appropriate treatment must be preceded by a correct diagnosis — treating the wrong disease helps no one.\u003c\/p\u003e\n\n\u003cp\u003eThe authors acknowledge that diagnosing axSpA remains challenging, even though diagnostic tools — including MRI and more readily available HLA-B27 testing — have clearly improved. The bigger unsolved problem is that many people with suspected axSpA never reach a rheumatologist in the first place; referral pathways remain imperfect.\u003c\/p\u003e\n\n\u003cp\u003eEven under almost optimal diagnostic circumstances, diagnostic uncertainty remains for a number of patients. This reflects the fundamentally heterogeneous nature of the disease. For patients in whom the diagnosis cannot be made with confidence, the authors advise doctors to:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eAvoid making a definitive conclusion one way or the other\u003c\/li\u003e\n  \u003cli\u003eRegularly discuss cases with fellow rheumatologists and radiologists, especially those with expertise in musculoskeletal radiology\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor now, the available data suggest that repeating MRI within one year has a low yield and is generally not diagnostically useful. In other words, a repeat scan after just a few months is unlikely to change the picture — patience and clinical follow-up matter more.\u003c\/p\u003e\n\n\u003ch2 id=\"practice\"\u003ePractice Points for Doctors (and What Patients Should Know)\u003c\/h2\u003e\n\n\u003cp\u003eThe article closes with practice points, which patients may find useful for understanding what a good diagnostic process should look like:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eNo single pathognomonic feature (a feature that alone proves the disease) exists for axSpA. Diagnosis is a skill that involves recognizing a pattern of features that, taken together, provides sufficient evidence.\u003c\/li\u003e\n  \u003cli\u003eA typical presentation in Western Europe is a young adult with chronic inflammatory back pain beginning before age 40–50, usually HLA-B27 positive, with one or two other SpA features and clear sacroiliitis on imaging.\u003c\/li\u003e\n  \u003cli\u003eBack pain that starts after age 45 is unlikely to be axSpA, where the vast majority (92% worldwide) of patients have symptom onset before 45.\u003c\/li\u003e\n  \u003cli\u003eClassification criteria are for research, not diagnosis; they misclassify too many individuals on both sides.\u003c\/li\u003e\n  \u003cli\u003eCounting SpA features helps but is insufficient — even with 4 or more features, about 15% of patients do not have axSpA, and a patient with peripheral SpA features plus back pain still needs an assessment of whether the back pain is truly axial.\u003c\/li\u003e\n  \u003cli\u003eMRI findings must be weighed against clinical suspicion, because BME appears in healthy people (23% of healthy volunteers in one Dutch study), runners (13–41%), and postpartum women (57% in a small study), often without deep lesions or erosions.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor patients, the most practical message from this paper is simple: a diagnosis of axSpA is a medical judgment that integrates your story, your examination, your blood tests, and your imaging — not any single one of those in isolation. If you are being evaluated for chronic back pain, a thoughtful rheumatologist will consider both what supports axSpA and what else could explain your symptoms. That balanced approach is the standard of care.\u003c\/p\u003e\n\n\u003c!-- ddn:faq:start --\u003e\n\u003ch2 id=\"ddn-faq\"\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eWhat is axial spondyloarthritis and how is it different from ankylosing spondylitis?\u003c\/h3\u003e\n\u003cp\u003eAxial spondyloarthritis is a chronic inflammatory disease mainly affecting the spine and sacroiliac joints. There are two subtypes: non-radiographic, with no visible changes on X-ray, and radiographic, formerly called ankylosing spondylitis, which shows definite sacroiliitis on X-ray. Symptoms and management are largely similar between forms.\u003c\/p\u003e\n\u003ch3\u003eWhat is inflammatory back pain and how is it recognized?\u003c\/h3\u003e\n\u003cp\u003eInflammatory back pain tends to be worse at rest, improves with exercise, and often wakes people in the second half of the night. It is recognized using five features: onset before age 40, gradual onset, improvement with exercise, no improvement with rest, and night pain. Having any four features identifies inflammatory back pain with 80% sensitivity and 74% specificity.\u003c\/p\u003e\n\u003ch3\u003eWhat do HLA-B27 blood test results mean for diagnosing axial spondyloarthritis?\u003c\/h3\u003e\n\u003cp\u003eHLA-B27 is the main genetic risk factor for axial spondyloarthritis. In a worldwide study, 65–89% of patients tested positive, depending on region, compared with about 6–8% of the general population in Europe and North America. A positive result meaningfully raises the chance of disease but is not a diagnosis by itself, since many HLA-B27-positive people never develop it.\u003c\/p\u003e\n\u003ch3\u003eCan an MRI alone confirm axial spondyloarthritis?\u003c\/h3\u003e\n\u003cp\u003eNo. MRI findings must be interpreted with clinical and laboratory information. Bone marrow edema, the key finding, also appears in healthy people, runners, and postpartum women. In one study, 23% of healthy volunteers had an MRI considered positive for sacroiliitis. Other causes of bone marrow edema, especially mechanical stress, must always be considered, and erosions are usually absent in healthy athletes.\u003c\/p\u003e\n\u003ch3\u003eWhat should I expect during a diagnostic evaluation for axial spondyloarthritis?\u003c\/h3\u003e\n\u003cp\u003eYour doctor will consider your age, symptoms, physical examination, blood tests for CRP and HLA-B27, and imaging. A history of inflammatory back pain, arthritis, psoriasis, inflammatory bowel disease, uveitis, family history, and response to NSAIDs helps build a pattern. The doctor will also look for other causes of back pain. A diagnosis is a medical judgment integrating all these factors, not any single test.\u003c\/p\u003e\n\u003ch3\u003eWhy might classification criteria not be used to diagnose my condition?\u003c\/h3\u003e\n\u003cp\u003eClassification criteria are designed for research, not for individual patient care. Using them as diagnostic tests misclassifies too many patients. In a meta-analysis of 4,990 patients, sensitivity was 82% and specificity 87%, meaning about 18 in 100 true cases are missed and 13 in 100 non-cases are falsely labeled. Real diagnosis requires clinical reasoning and excluding other causes.\u003c\/p\u003e\n\u003ch3\u003eWhen should someone with suspected axial spondyloarthritis seek a second opinion about the diagnosis?\u003c\/h3\u003e\n\u003cp\u003eDiagnosis requires recognizing a pattern across history, exam, blood tests, and imaging; no single feature is enough. A second opinion is important if the diagnosis rests only on research classification criteria, a simple count of features, or imaging findings alone, since these approaches misclassify patients. MRI findings can appear in healthy people and athletes, and many patients do not fit a typical picture. If back pain started after age 45, or no inflammatory changes are seen, diagnostic uncertainty remains. Diagnostic Detectives Network provides independent expert second opinions.\u003c\/p\u003e\n\u003c!-- ddn:faq:end --\u003e\n\n\u003ch2 id=\"source\"\u003eSource Information\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eOriginal article title:\u003c\/strong\u003e Challenges in the diagnosis of axial spondyloarthritis\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eJournal:\u003c\/strong\u003e Best Practice \u0026amp; Research Clinical Rheumatology, Volume 37 (2023), Article 101871\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDOI:\u003c\/strong\u003e https:\/\/doi.org\/10.1016\/j.berh.2023.101871\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAccess:\u003c\/strong\u003e © 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:\/\/creativecommons.org\/licenses\/by\/4.0\/).\u003c\/p\u003e\n\u003cp\u003eThis patient-friendly article is based on peer-reviewed research. It is provided for educational purposes and does not replace individual medical advice. Anyone experiencing chronic back pain should discuss their symptoms with a qualified physician.\u003c\/p\u003e","brand":"DiagnosticDetectives.Com","offers":[{"title":"Default Title","offer_id":47549381836956,"sku":null,"price":0.0,"currency_code":"RUB","in_stock":true}],"url":"https:\/\/diagnosticdetectives.ru\/products\/axial-spondyloarthritis-understanding-the-challenges-doctors-face-in-making-the-diagnosis","provider":"DiagnosticDetectives.Com","version":"1.0","type":"link"}