What are the diagnostic criteria and treatment options for a young to middle-aged male patient presenting with chronic back pain and stiffness, particularly in the morning or after periods of inactivity, with a potential family history of ankylosing spondylitis?

Ankylosing Spondylitis Diagnosis

In a young to middle-aged male with chronic back pain, morning stiffness improving with exercise, and potential family history, you should immediately suspect axial spondyloarthritis and initiate a structured diagnostic workup starting with plain radiographs of the sacroiliac joints, HLA-B27 testing, and inflammatory markers. 1

Recognizing Inflammatory Back Pain

The key to early diagnosis is distinguishing inflammatory from mechanical back pain. Inflammatory back pain has five cardinal features: 2, 1

• Insidious onset before age 40-45 years 2, 3
• Morning stiffness lasting >30 minutes that improves within an hour after movement 1, 3
• Pain worsening at night (particularly second half of night) and improving with activity, not rest 1, 3
• Alternating buttock pain indicating sacroiliac joint involvement 3
• Improvement with exercise but no improvement with rest 2, 1

Inflammatory back pain is present in 70-80% of patients with axial spondyloarthritis, though it also occurs in 5-6% of the general population, requiring further workup to confirm diagnosis. 2

Initial Diagnostic Workup

Order these tests before rheumatology referral: 4

• Plain radiographs of sacroiliac joints as first-line imaging (sensitivity 66%, specificity 68% for sacroiliitis grade ≥2 bilateral or grade ≥3 unilateral) 2, 3
• HLA-B27 testing (positive in 74-89% of patients; post-test probability of 32% when positive in chronic back pain patients) 2, 1
• ESR and CRP (though normal in 50% of cases, so cannot rule out disease if negative) 1, 4
• Complete blood count 4

Critical Diagnostic Pitfall

Do not rule out axial spondyloarthritis based solely on negative HLA-B27 or normal inflammatory markers—10% of patients are HLA-B27 negative and 50% have normal inflammatory markers despite active disease. 4 This is the most common reason for the typical 5-7 year delay between symptom onset and diagnosis. 4, 3

When Radiographs Are Negative or Equivocal

If clinical suspicion remains high but radiographs are normal, order MRI of sacroiliac joints. 1, 3 MRI can detect early inflammatory changes (bone marrow edema on STIR or T2 sequences with fat saturation) before structural damage appears on plain films, with sensitivity of 78% and specificity of 88%. 3 Radiographic changes evolve slowly over years, and some symptomatic patients never develop radiographic sacroiliitis. 2

Mandatory Rheumatology Referral Criteria

Refer to rheumatology when the patient has chronic low back pain (>3 months) starting before age 45 PLUS at least 4 of the following: 4

• Back pain occurring before age 35
• Waking at night due to back pain
• Buttock pain
• Improvement in pain with movement or within 2 days of taking an NSAID
• First-degree relative with spondyloarthritis
• Current or previous arthritis, enthesitis, or psoriasis

Also refer immediately if: 4

• HLA-B27 positive with chronic back pain
• Evidence of sacroiliitis on x-ray or MRI
• Persistently high disease activity despite 2-4 weeks of optimal NSAID therapy
• Difficulties performing activities of daily living despite NSAID treatment

Screening for Extra-Articular Manifestations

Screen for acute anterior uveitis, which occurs in up to 40% of patients and represents the most frequent extra-articular manifestation. 1 Early detection is crucial to prevent vision loss, and prompt ophthalmologic referral is necessary if identified. 1

Also assess for inflammatory bowel disease and psoriasis, which are associated conditions. 4

Initial Management While Awaiting Rheumatology

Start NSAIDs at the lowest effective dose, then titrate to maximum tolerated doses while weighing cardiovascular, gastrointestinal, and renal risks. 4 Approximately 75% of patients show good or very good response within 48 hours of full-dose NSAID therapy. 4 Continuous NSAID use is preferred over on-demand dosing for patients who respond well and remain symptomatic. 4

If the first NSAID is ineffective after 2-4 weeks, trial a different NSAID before escalating therapy. 4 For patients with gastrointestinal risk factors, consider COX-2 selective NSAIDs or add gastroprotective agents. 4

Refer all patients to structured exercise programs, as these are more beneficial than home exercises alone. 4 Physical therapy should be considered for all patients. 4

Disease Activity Assessment

Once diagnosed, disease activity is monitored using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), which evaluates fatigue, spinal pain, peripheral joint pain, and morning stiffness. 3 A score >4 indicates active disease requiring treatment escalation. 3

Treatment Escalation Beyond Primary Care

For patients with persistently high disease activity despite NSAIDs and physical therapy, biologic DMARDs (TNF inhibitors or IL-17 inhibitors) become the next treatment step. 4, 5 Do not use conventional DMARDs (methotrexate, sulfasalazine, leflunomide) for purely axial disease—they are ineffective. 4 Sulfasalazine may only be considered if peripheral arthritis is present. 4