A-230 Establishing an Optimal HIT Optical Density Value: A Six Year Study

Abstract

Background Our core laboratory provides Heparin Induced Thrombocytopenia antibody (HIT) laboratory screening to patients across our health system. Our enzyme-linked immunosorbent assay (ELISA) format can be reported using a Positive or Negative result and in raw optical density (OD) units. We validated an optimal HIT OD value for our providers that correlated with a positive HIT confirmatory assay result. Reporting the HIT OD value can bring greater confidence to clinicians, since a high HIT OD value strongly correlates to positive HIT confirmatory value by serotonin release assay (SRA), especially if the patient’s clinical score (i.e. 4Ts Score) is intermediate or high. Methods A polyspecific (IgG, IgM, IgA) HIT test using ELISA methodology was used for HIT screening (Asserachrom HPIA, Diagnostica Stago, Inc., Parsippany NJ, USA). HIT OD values were determined using a a VersaMax Microplate reader at a wavelength of 450 nm. Six years of positive HIT OD patient data was analyzed for mean average OD value, distribution of the OD values across the positive reportable range, and correlation with Serotonin Release Assay (SRA) results. ROC data analysis was performed for determination of the optimal HIT OD cutoff correlating with positive confirmatory SRA result. Results We determined a HIT OD of 1.281 with an optimal sensitivity of 85.7% and specificity of 82.7%. Conclusion A HIT OD value was determined with peak sensitivity and specificity versus a positive SRA value. Since SRA testing often takes days to complete at an outside reference laboratory, having an optimal HIT OD value can better predict a positive SRA result and can help diagnose HIT with a faster turnaround time, allowing for better patient management and therefore potential improved patient outcomes.