Ocular pulse amplitude as a diagnostic adjunct in giant cell arteritis

BACKGROUND: To develop an algorithm based on the ocular pulse amplitude (OPA) to predict the probability of a positive temporal artery biopsy (TAB) result in the acute phase of suspected giant cell arteritis (GCA). METHODS: Unilateral TAB was performed and ipsilateral OPA measurements were taken by Dynamic Contour Tonometry. Among the clinical signs and laboratory findings tested in univariate analyses, OPA, Erythrocyte Sedimentation Rate (ESR) and thrombocyte count showed a strong association with a positive TAB result. Algorithm parameters were categorized into three groups (OPA >3.5, 2.5-3.5, and 60 mm/h; thrombocyte count 500'000/μl). Score values (0, 1, and 2) were attributed to each group, resulting in a total score range from 0 to 6. A univariate logistic regression analysis using the GCA diagnosis as the dependent and the total score as the independent variate was fitted and probability estimates were calculated. RESULTS: Thirty-one patients with suspected GCA undergoing TAB during an eighteen-month observation period were enrolled. Twenty patients showed histologically proven GCA. Four patients had score values ≤2, fourteen between 3 and 4, and thirteen of ≥5. The corresponding estimated probabilities of GCA were95%. CONCLUSION: The present study confirms previous findings of reduced OPA levels, elevated ESR, and elevated thrombocyte counts in GCA. It indicates that a sum score based on OPA, ESR, and thrombocyte count can be helpful in predicting TAB results, especially at the upper and the lower end of the sum score range