In a patient with ankylosing spondylitis and a positive FABER (Flexion, Abduction, and External Rotation) test, what is the recommended treatment?

Treatment for Ankylosing Spondylitis with Positive FABER Test

In a patient with ankylosing spondylitis and a positive FABER test (indicating active sacroiliitis), initiate NSAIDs as first-line therapy, and if isolated sacroiliitis persists despite NSAIDs, add locally administered intra-articular glucocorticoid injection to the sacroiliac joint. 1

Understanding the Clinical Context

A positive FABER test in ankylosing spondylitis indicates active sacroiliitis—inflammation of the sacroiliac joints. This is a specific manifestation that requires targeted treatment beyond general axial disease management. The FABER test has demonstrated 76.2% sensitivity and 66.2% specificity for detecting MRI-confirmed sacroiliitis 2, making it a clinically useful sign that should prompt specific therapeutic intervention.

Treatment Algorithm

Step 1: Initial Pharmacological Management

Start with NSAIDs immediately as the strongly recommended first-line pharmacological treatment for active ankylosing spondylitis 1. The guidelines are clear:

• No particular NSAID is preferred—choose based on patient tolerance and comorbidities 1
• Use continuous dosing (not on-demand) for active disease to control symptoms 1
• Consider selective COX-2 inhibitors in patients at high risk for gastrointestinal or cardiovascular adverse events 3
• Allow at least 1 month of continuous NSAID therapy (trying at least two different NSAIDs for 15 days each) before declaring NSAID failure 3

Step 2: Add Local Glucocorticoid Injection for Persistent Isolated Sacroiliitis

If isolated active sacroiliitis persists despite adequate NSAID trial, conditionally recommend locally administered parenteral glucocorticoids to the sacroiliac joint 1. This is specifically indicated when:

• The patient has isolated active sacroiliitis (positive FABER test)
• Axial disease is otherwise stable
• NSAIDs have been tried adequately but sacroiliac pain persists

The injection should be performed under fluoroscopic guidance or CT guidance for accurate placement 4.

Step 3: Escalate to Biologic Therapy if Needed

If the patient has active axial disease beyond just sacroiliitis (not responding to NSAIDs), escalate to biologic therapy:

• TNF inhibitors (TNFi) are strongly recommended as the preferred biologic option 1
• No particular TNFi is preferred—all are equally effective 1
• IL-17 inhibitors (secukinumab or ixekizumab) are also strongly recommended but TNFi are conditionally preferred over IL-17i as first-line biologics 1

Important caveat: Biologic therapy is indicated when disease activity score (ASDAS) ≥2.1 AND the patient has failed ≥2 NSAIDs AND has objective evidence of inflammation (elevated CRP, MRI inflammation, or radiographic sacroiliitis) 5.

Critical Management Points

What NOT to Do

• Strongly recommend AGAINST long-term systemic glucocorticoids—the risks outweigh benefits in axial spondyloarthritis 3, 1
• Do NOT use conventional synthetic DMARDs (sulfasalazine, methotrexate) for pure axial disease—these are only conditionally recommended for prominent peripheral arthritis 1

Essential Non-Pharmacological Management

Physical therapy is strongly recommended and should be initiated concurrently with pharmacological treatment 1:

• Active/supervised exercise programs are preferred over passive modalities (massage, ultrasound, heat) 1
• Land-based exercises are conditionally preferred over aquatic therapy 1
• Emphasize consistent exercise, stretching, and posture maintenance 6

Monitoring Strategy

• Use ASDAS or SASDAS plus CRP/ESR to monitor disease activity at regular intervals 3
• Target sustained low disease activity or remission 3
• Do NOT routinely repeat MRI or radiographs for monitoring stable disease 3, 1

Special Considerations

If Extramusculoskeletal Manifestations Present

Modify biologic choice based on comorbidities 5:

• Recurrent uveitis or IBD: Use TNF monoclonal antibodies (infliximab, adalimumab, golimumab)—NOT etanercept
• Significant psoriasis: IL-17 inhibitors are preferred

Common Pitfalls to Avoid

1. Don't confuse isolated sacroiliitis with generalized active axial disease—the former may respond to local injection, while the latter requires systemic biologic therapy
2. Don't use on-demand NSAIDs for active disease—continuous dosing is needed for symptom control
3. Don't inject peri-tendon areas (Achilles, patellar, quadriceps tendons) if enthesitis is present—only intra-articular or direct entheseal injections are appropriate 1
4. Don't delay physical therapy—it should start immediately, not after pharmacological optimization

Evidence Quality Note

The recommendation for local glucocorticoid injection in isolated sacroiliitis carries very low quality evidence 1, but represents expert consensus based on clinical experience with inflammatory joint disease management. The stronger evidence supports NSAIDs and TNFi for overall disease management.