Proficiency test performance and experience with College of American Pathologists' programs

We examined rates of unacceptable results in a large interlaboratory proficiency test program, which is designed for small hospitals, clinics, and physician offices. The objective was to see whether rates of unacceptable results decrease as laboratories gain experience in interlaboratory comparison programs. We examined data from the College of American Pathologists' Excel Surveys, 1987 through 1993, in the areas of chemistry, hematology, immunology, and blood bank. The data for laboratories with consistent participation show consistent and statistically significant improvement in performance for the first 3 to 4 years of proficiency testing. The data for all participants also suggest that laboratories with more experience with proficiency testing have lower rates of unacceptable results, and that these rates tend to decrease with each year of experience. These conclusions support the findings of other researchers who have documented the benefits of interlaboratory comparison programs and proficiency testing.