Population-Based Performance of Inflammatory Markers in Giant Cell Arteritis

Area of Science:

• Rheumatology
• Clinical Immunology
• Epidemiology

Background:

• Giant Cell Arteritis (GCA) is a systemic vasculitis affecting large arteries.
• Accurate diagnosis of GCA is crucial to prevent complications such as vision loss.
• Inflammatory markers are commonly used as diagnostic aids, but their population-based performance in GCA requires detailed evaluation.

Purpose of the Study:

• To assess the population-based diagnostic performance of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and platelet count in patients undergoing temporal artery biopsy (TAB).
• To determine the sensitivities and specificities of individual and combined inflammatory markers for GCA diagnosis.

Main Methods:

• A retrospective, population-based, cross-sectional study was conducted using data from Olmsted County, Minnesota (1995-2019).
• Patients who underwent TAB were classified as GCA or non-GCA based on the 1990 American College of Rheumatology criteria.
• Sensitivity and specificity of CRP, ESR, and platelets were calculated for GCA diagnosis.

Main Results:

• Of 553 patients (143 GCA, 410 non-GCA), those with GCA showed significantly higher CRP, ESR, and platelet levels.
• Individual marker sensitivities were: CRP 96%, ESR 80%, platelets 49%. Specificities were: CRP 21%, ESR 43%, platelets 79%.
• Combined markers showed improved performance, with ESR, CRP, and platelets achieving 41% sensitivity and 84% specificity. Notably, 3% of GCA patients had normal inflammatory markers.

Conclusions:

• Inflammatory markers, including CRP, ESR, and platelets, are valuable in the diagnostic workup of GCA.
• Normal inflammatory marker levels do not exclude a diagnosis of GCA, underscoring the importance of clinical judgment and other diagnostic tools.
• The study provides population-based data on the diagnostic utility of inflammatory markers in GCA.