A-144 Is the Q Flag (Blast/Abn Lympho) a sensitive tool for detecting a hematological neoplasm?

Abstract Background Automated hematology analyzers produce accurate WBC differential counts for normal and abnormal values.They flag also the pathological cells to notify the user that the differential may be inaccurate. The counters display Q-flags for Blast/Abnormal Lymphocytes, left shift, and atypical lymphocytes if an abnormal WBC cell population is found. The aim is to compare the sensitivity and specificity of Q-flag for Blast/Abnormal Lymphocytes to the gold standard (flow cytometry) and establish a laboratory detection threshold of Q-flag (Blast/Abn Lympho) for hematological neoplasm (HN). Methods A retrospective cross-sectional study was done at the Department of Laboratory Medicine, AIIMS, New Delhi. Patient’s EDTA blood samples run on the Sysmex XN series (XN-10 module) hematology analyzer were screened for 20 consecutive days. 312 samples with a Q-flag for Blast/Abnormal lymphocyte threshold of >100 were included. Out of these only 67 patients had flow cytometry findings, which were further analyzed. Statistical analyses were done using STATA version 14.0. Rank-sum test, ROC analysis and Youden index criteria were used for calculating sensitivity, specificity and optimal threshold. Results Of 67 samples with flow cytometry data, 49 patients showed blasts in the Q flag and flow cytometry. In hematological neoplasm, the mean Q-flag for blast/abnormal lymphocyte was greater than in non-hematological neoplasm (274.04±44.06 vs. 182.70±77.62) by using t-test and the p-value was significant. Based upon Youden index the threshold =230 was taken.The ROC analysis showed sensitivity of 84% (70.3%-92.7%), specificity of 67%(41%-86.7%) and AUC= 0.76 (0.628-0.875) for Blast/Abn lymphocyte flag at >230 cutoff. Conclusion Q-Blast/Abn Lympho flag threshold >230 may be used as an initial tool for detecting hematological neoplasm. Q-flag by reducing TAT may facilitate early patient diagnosis and initiation of therapy. Limitation: The findings obtained in our study need to be confirmed in a large sample size.Other Q-flags, such as left shift and atypical lymphocyte, were not assessed together in our study. Q Flag for blast/abnormal lymphocyte is a proprietary parameter that may not be available in all instruments.