Abstract:Objective：To investigate the variation components of the uncertainty of alanine aminotransferas（ALT）measurement before the analysis in blood services laboratory. Methods：According to the requirement of the physical examination of blood donors（GB18467-2011），a total of 240 voluntary blood donors eligible for multiple free voluntary donation were randomly selected as study object. The blood samples were treated at different separation interval，at different storage condition，at different centrifugation temperatures，at different collection tubes（anticoagulant tube v.s. coagulant tube），and underwent centrifugation after storage or before storage. The variance of each group and undifferentiated group was statistically analyzed by SPSS 20.0 software. For statistically significant components，the uncertainty before the analysis can be calculated by the non-negligible component. Results：The results of ANOVA showed that there were statistical differences between the groups coping with different sequence of centrifugation and storage，between the goups at different storage temperature，with different time intervals between sample collection and separation，and at different centrifugation temperatures（P < 0.05）. Only the groups using different collection tubes showed no statistical difference（P > 0.05）. The results indicated that the sequence of centrifugation and storage，storage temperature，time intervals and centrifugation temperature could influence the uncertainty of ALT measurement. Conclusions：The pre-analysis components，such as sequence of centrifugation and storage，storage temperature，time intervals and centrifugation temperature，should be strictly controlled . The uncertainty assessment before the analysis is not negligible.