Proficiency testing of platelet counting in Ontario

Proficiency testing results provide data for interlaboratory comparisons. The Laboratory Proficiency Testing Program of Ontario, Canada, has tested platelet counting for a decade and other hematology parameters for 15 years. Despite the fact that all testing programs are compromised by the type of testing material used, for platelet count testing, conclusions are possible. The data indicate that most laboratories in Ontario have greater difficulty performing reproducible platelet counting as compared with other components of hematologic cytometry. A major contributor to this shortfall is the method used by the laboratory. It was not a surprise that manual counting had a high coefficient of variation. Unexpectedly, the semiautomated methods used in the mid-1980s also displayed a high coefficient of variation.