Normal inflammatory markers in giant cell arteritis: a diagnostic blind spot

Area of Science:

• Rheumatology
• Vascular Medicine
• Diagnostic Imaging

Background:

• Giant cell arteritis (GCA) is a critical vasculitis requiring prompt diagnosis.
• Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) are key diagnostic markers, but some GCA patients exhibit normal levels.
• This variability necessitates exploring alternative diagnostic approaches when inflammatory markers are inconclusive.

Purpose of the Study:

• To compare the clinical presentation and vascular ultrasound findings in GCA patients with normal versus elevated inflammatory markers.
• To evaluate the diagnostic accuracy of ESR and CRP in detecting GCA.
• To identify factors associated with normal inflammatory markers in GCA patients.

Main Methods:

• Retrospective analysis of GCA patients diagnosed via a Fast Track Clinic (FTC).
• Comparison of clinical presentation and ultrasound results between GCA patients with normal (n=23) and elevated (n=107) inflammatory markers.
• Calculation of ESR and CRP sensitivity and specificity using an additional 159 non-GCA patients.

Main Results:

• C-Reactive Protein (CRP) showed 74% sensitivity and 49% specificity; Erythrocyte Sedimentation Rate (ESR) demonstrated 48% sensitivity and 72% specificity for GCA detection.
• Patients with normal inflammatory markers had a significantly longer duration between symptom onset and marker measurement (35 vs. 20 days).
• No significant differences in clinical presentation were observed between GCA patients with normal or elevated inflammatory markers.

Conclusions:

• GCA patients exhibit similar clinical presentations irrespective of their inflammatory marker status.
• A prolonged interval from symptom onset to inflammatory marker testing is associated with normal ESR and CRP levels in GCA.
• Low inflammatory marker levels should not deter a comprehensive diagnostic work-up for GCA.