Abstract: Objective To improve the work efficiency and ensure the accuracy of the blood test through establishing an appropriate standard of microscopic examination based on setting up reasonable threshold values to suspicious alarm informations (Q-flags) in Sysmex XE-2100 automatic hematology analyzer. Methods A total of 4 500 specimens from the out-patient and emergency departments and the in-patient department during March 2011 to March 2012 underwent the measurement by Sysmex XE-2100 with blood slide, subsequent staining and manual microscopic examination. The positive standard was set up as follows: blast cell ≥1%,promyelocyte and myelocyte ≥ 1%, metamyelocyte > 2%,stab granulocyte > 5%,atypical lymphocyte > 5% and nucleated erythrocyte ≥ 1%. According to these positive standards, the threshold valus of the main parameters in the Q-flags were redefined. Finally, 1 400 specimens were measured to verify the reliability of the newly established cut-off value. Results (1) Threshold values before/after amendment were: blast cell 100/130, immature granulocyte 100/150, left shift 100/160, atypical lymphocyte 100/180, nucleated erythrocyte 100/90 and abnormal/blast lymphocyte 100/200. (2) False positive rates (%) before/after amendment were: 61.05/50.15, 56.36/35.60, 44.34/14.10, 62.12/32.20, 36.18/40.61 and 62.96/26.30. Real negative rates (%) before/after amendment were: 38.95/49.85, 43.64/64.36, 55.66/85.90, 37.88/67.80, 63.82/59.39 and 37.04/73.70. Total coincidence rates(%) before/after amendment were : 47.75/56.42, 57.00/71.83, 73.44/89.67, 45.33/71.33, 80.17/79.17 and 43.33/76.00. The alarm rate decreased by 14.67%. (3) There were no initial leukemic cells omitted in the validation test. Conclusions (1) Amending reasonable threshold values of Q-flags in Sysmex XE-2100 can effectively filter out the truly abnormal samples and ensure the accuracy of blood test results. The selected and targeted microscopic examination of the smeared blood specimen can greatly improve work efficiency. (2) The threshold values of the Q-flags in automatic blood cell analysis system should be revised according to the practical situation for each laboratory. Original factory value cannot be directly used.

Key words: Automatic hematology analyzer, Alarm information, Threshold value