Role of thrombocytosis in diagnosis of giant cell arteritis and differentiation of arteritic from non-arteritic anterior ischemic optic neuropathy

To investigate the role of thrombocytosis in the diagnosis of giant cell arteritis (GCA), and differentiation of arteritic (A-AION) from non-arteritic (NA-AION) anterior ischemic optic neuropathy; and comparison of the sensitivity and specificity of platelet count to that of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and some other hematologic variables in the diagnosis of GCA. This retrospective study is based on 121 temporal artery biopsy confirmed GCA patients and 287 patients with NA-AION seen in our clinic. For inclusion in this study, all GCA patients, at their initial visit, prior to the initiation of corticosteroid therapy, must have had ESR (Westergren), platelet count and complete blood count, and temporal artery biopsy. From 1985 onwards CRP estimation was done. For inclusion in this study, all NA-AION patients at the initial visit must have undergone evaluation similar to that described above for GCA, except for temporal artery biopsy. Wilcoxon rank-sum test and the two-sample t-test were used to compare hematologic variables between GCA patients with and without visual loss, between those with and without systemic symptoms, and also between GCA and NA-AION patients. Pearson correlation coefficient was computed to measure the association of platelet counts and the other hematologic variables with ESR. Receiver operating characteristic (ROC) curves were constructed for ESR, CRP, platelet count, combinations of ESR and platelet count, and CRP and platelet count, hemoglobin, hematocrit, and white blood cell (WBC) count and the area under the curve (AUC) were compared. Comparison of ESR, CRP, and hematologic variables of GCA patients and of A-AION with the NA-AION group, showed significantly (p