Proficiency Testing Performance in US Laboratories: Results Reported to the Centers for Medicare & Medicaid Services, 1994 Through 2006

Abstract

Abstract Context.—Beginning in 1994, clinical laboratories performing nonwaived testing were required, under the regulations implementing the Clinical Laboratory Improvement Amendments of 1988 (CLIA), to enroll and participate in a proficiency testing (PT) program approved by the Centers for Medicare & Medicaid Services. Successful PT performance is a requirement for maintaining CLIA certification to perform testing in certain specialties and subspecialties and for specific analytes. Objective.—To evaluate the PT performance from 1994 through 2006 of hospital and independent laboratories (HI) compared with all other testing sites (AOT) for selected commonly performed tests and analytes. Design.—Proficiency testing data, from 1994 through 2006, were electronically reported to the Centers for Medicare & Medicaid Services by approved PT programs as required by CLIA regulations. Approximately 16 million PT event scores from 36 000 unique testing sites were sorted into 2 groups based on the type of testing facility: HI or AOT. Results.—The PT performance scores for 15 of the most commonly performed tests demonstrated a decline in failure rates for both HI and AOT laboratory groups during 1994 through 2006 (analyte/test values reported in this article include alanine aminotransferase, amylase, bilirubin, cholesterol, digoxin, glucose, hemoglobin, leukocyte count, potassium, prothrombin time, theophylline, thyroxine, triglycerides, white blood cell differential, and uric acid). For most analytes, the difference in failure rates between HI and AOT was statistically significant. The AOT group started with higher failure rates, and remained higher for all analytes, during most years when compared with the HI group; although, over time, that difference diminished. The AOT group showed a greater decline in PT failure than the HI group. For all analytes, the AOT group performance improved during this period. Conclusions.—The PT performance improved dramatically for the AOT group from 1994 through 2006 as measured by a decrease in the percentage of laboratories with unsatisfactory performance for 15 selected analytes. The PT performance in the HI group improved modestly for some analytes during this same period, whereas, for other analytes, the group showed no apparent improvement.