Investigation and analysis of current situation about reference intervals of lymphocyte subsets by flow cytometry tests in China

Objective Discussthe reference intervals and their sources of lymphocyte subsets by flow cytometry tests by all Chinese clinical laboratories at 2014 with a comparison of difference between different test systems. Methods Questionnaires about reference intervals were distributed to 212 clinical laboratories participating in October 2014 national external quality assessment scheme of lymphocyte subsets by flow cytometry tests of National Center for Clinical Laboratory. Relevant information about reference intervals of 5 relative counting items CD3+ (%), CD3+ CD4+ (%), CD3+ CD8+ (%), CD3-CD16+ CD56+ (%) and CD3-CD19+ (%) was collected by a internet-based external quality assessment software systems. Microsoft Excel 2010 and SPSS 19.0 were used to sort out raw data, eliminate unreasonable or incorrect data, and only analyze source distribution, arithmetic average, median, minimum value, maximum value and percentiles (P2.5 and P97.5) of upper and lower limits about healthy adults' reference intervals.Laboratories derived from the highest percentage of source distribution whose reagent and instrument were matching with each other were grouped according to the test systems used and the differences of reference intervals between different systems were compared with Mann-Whitney test. Results For five items collected, in the clinical laboratories who accepted statistical analysis, respectively 39.32% (81/206), 37.44% (79/211), 37.68% (78/207), 37.11% (72/194), 36.98% (71/192)of them had verified the reference intervals they used. The top three sources of reference intervals were instructions of reagent and instrument manufactures (49.70%-52.54%), calculations by laboratories themselves (18.64%-20.00%), and calculations by other laboratories (14.12%-15.43%). The arithmetic averages and medians of upper and lower limits about every item were relatively close. But the minimum and maximum values of upper and lower limits of certain items had moderate differences. As Mann-Whitney test later showed, all items with the P values of upper and lower limits between different test systems, except for the lower limit of CD3+ CD4+ (%) (P value is 0.052) and the upper limit of CD3-CD19+ (%) (P value is 0.117), were lower than 0.05 which meant an existing statistical difference. Conclusions The sources of lymphocyte subsets by flow cytometry tests in all Chinese clinical laboratories were different and the instructions of reagent and instrument had the highest percentage, but the reference intervals among different test systems had statistically significance.(Chin J Lab Med, 2016, 39: 356-360) Key words: Flow cytometry; Lymphocyte subsets; Reference values; Quality control