To Evaluate the Sensitivity of Rosner’s Index (ICA) Vs Standard Normalised Ratio in the Interpretation of Mixing Studies in Lupus Anticoagulant

Abstract

Introduction: The Current 3 major LAC guidelines (BSH, ISTH & CLSI) recommends mixing tests for detection of LAC, even though these test order/ sequence vary & there are certain limitations, but still these guidelines advocates mixing test so as to maximize the diagnostic performance. The main objective of this study is to assess sensitivity of these tests in 255 LAC cases. Results: The Coagulometer used is Sysmex CS-5100. RI Cut offs ≤ 10 = Correction & ≥ 15 = Inhibitor & SNR > 1.15 indicates inhibitor. Of 255 LAC cases RI showed a sensitivity of 72% in correctly detecting LAC were as 11.7% were indeterminate & 15% were wrongly interpretated as factor deficiency. SNR showed a sensitivity of 83% in correctly detecting LAC were as 10.9% were indeterminate & 5.8% were wrongly interpretated as factor deficiency. Discussion: BSH & ISTH guidelines recommends Standardised Normalised ratio (mixing test-specific cut off) and Rosners index (ICA) for interpretation of mixing test results in detecting LAC.This study shows that SNR is more sensitive than RI for detecting LAC while interpretating Mixing test results. This study was in correlation with Moore & Kumano's study. Conclusion: It is difficult to interpretate mixing study results in LAC patients. It is valuable to maximise mixing test interpretation as the dilution can lead to false-negative results .RI & SNR were comparatively analysed for their sensitivity to detect LAC in mixing studies & these data applied with the reagents and equipment employed, SNR was found to be more sensitive as compared to RI.