Lawrence Oh1,2, Eugene Wong1,2, Anthony Gill1,3, Peter McCluskey2,4, James Smith1,4

Purpose: To determine whether the ratios derived from the complete blood count such as neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR), which are associated with other inflammatory disorders, was also a helpful predictor in Giant Cell Arteritis (GCA) in addition to the more traditional markers, such as ESR and CRP.

Methods: We performed a retrospective case-control study of a consecutive cohort of 537 patients over 6 tertiary hospitals that had undergone a Temporal Arter Biopsy (TAB) from 1^st January 1992 to 1^st December 2015. TABs were performed on all patients clinically suspected of having GCA. Patients were categorised as either positive or negative based on the presence of granulomatous inflammation. In these patients, we also collected age, sex, ESR, CRP, platelets, lymphocytes and monocytes.

Results: 537 patients were included in the final analysis. Using univariate analysis, we found that NLR (OR 1.81, p=0.02) and PLR (OR 3.25, p<0.001) were statistically significant predictors for GCA, while MLR (1.55, p=0.10) showed an insignificant association. As expected, we also found that ESR (OR 3.62, p<0.001), CRP (OR 3.00, p<0.001) and thrombocytosis (OR 4.44, p<0.001) were statistically significant for GCA.

Conclusion: NLR, PLR, Platelets, ESR and CRP were found to be statistically significant predictors of GCA. This highlights the new diagnostic potential of the complete blood count in GCA that has never been explored. We are excited by this finding as the complete blood count is an inexpensive test that is already ubiquitously utilised in patients presenting with symptoms of GCA.