Comparison between the Precision of Measurements in Two Types of the Micropipettes according to CLSI EP5 and ISO 8655

Background: In the diagnosis medical labs, it is very important to evaluate the precision ofmicropipettes in transferring small amounts of liquids. The medical tests will not result accurately, ifthe liquid volume doesn’t transfer exactly by micropipettes. Thus the doctor faces sort of problems inthe disease diagnosis and its control. In the standard CLSI EP5, there is a method to specify and assessthe precision of micropipettes, by using CV (coefficients of variation). Also there are other methods toestimate and test the mention CV theory, in the formal statistic texts which could be used to assess themicropipettes precision. It is the main goal of this research to study the precision of lab micropipetteswhich are shown by A and B and compared by reference standard value from ISO 8655.Material and Methods: In this research we evaluate the precision of the lab micropipettes. Twobrands A and B are assigned to measure the distilled water mass by using the accurate scale which isaccurate up to 10-6 to measure 50 gram weight. The experimental environment is a metrology labwhich is confirmed by Iran Standard and Industrial Researches. A unique technician sampled in thebeginning of the work time and after 2 hours repeated the sampling. Totally, each micropipette is usedto measure 40 times with 10 times repeat for single measurement in 28 work days. It is used commonstatistical methods to estimate and test the coefficients of variation theory.Results: Point estimation of CV for micropipettes A and B were 0.50% and 0.64% respectively.Also the 95% confidence upper bounds for these two micropipettes by using likelihood ratio methodwere 0.53% and 0.64% respectively. The micropipette A confirmed the ISO 8655, but the micropipetteB did not. Measurement error in micropipette B was 30% less than micropipette A in average.Conclusion: By using the approach of CLS EP5 and confidence interval for CV, precision of twomicropipettes were compared. Only one of them confirmed the ISO 8655, but the other one was failed .