Proficiency testing programs--promises, progress, and problems. A 40-year prospective.

Proficiency testing as a means of interlaboratory improvement is over 40 years old. Proficiency testing as a tool of the regulatory process is nearly 20. While successful, ie, the quality of laboratory work in the United States has improved significantly during the past 40 years, this union of regulation and education continues to be a marriage of unequals. Clearly, those who started the professional laboratory community on the road to interlaboratory proficiency testing envisioned a promise of improved quality. The promise is fulfilled; even on an interlaboratory basis, the quality of work (precision) approaches or even exceeds the clinicians' requirements for medically useful data. Major problems continue to exist: the prospect of regulating a vast population of "physicians' office laboratories" presents new challenges for program providers, and as methodologies in laboratories have improved, some of the long-held systems of grading and performance evaluation are beginning to fail. The failure is not one of intent, logistics, or statistics. Proficiency testing, as a fine sharp tool, is corrupted when applied in a situation in which it is ill suited to perform. New knowledge will renew the promise and allow the professional, clinical laboratory community to progress.