[Definition of maximum permissible errors for major physical parameters affecting the result of microplate ABO-RH1...

Metrological survey of analytic equipment is developing well in French blood bank laboratories, but still the limits of critical parameters affecting the result of basic methods are usually not defined. The aim of this study is to establish experimentally maximum permissible errors for critical physical values involved in microplate ABO-RH1 blood grouping, such as temperature and time of incubation and volumes of reagents and blood samples.

Samples were internal quality controls used routinely in the laboratory. Three set points were defined for each parameter: incubation temperature 18, 22 and 26 degrees C; incubation time 10, 15 and 20 min; reagent sera and sample cells volume 20, 30 and 40 microL; reagent cells volume 15, 20 et 25 microL; plasma sample volume 30, 40 et 50 microL. All equipments (temperature test chamber, chronometer and pipettors) were calibrated using national standards (COFRAC) according to appropriate methods for estimation of uncertainty of measurement. Significant components of uncertainty were taken into account to define a global uncertainty for each measurable quantity.

All tests results from any combination of the above set points (n=81 for each sample tested in triplicate) were consistent with the expected result. Not one undetermined result was observed.

The experimental design of this study allowed us to define accurately maximum permissible errors for major critical parameters involved in microplate ABO-RH1 blood grouping. Hence these values must be applied to metrological survey of the equipment. Further, our study demonstrates the robustness of the method.