A user's classification of problems identified by proficiency testing surveys.

Laboratory results judged as unacceptable in external proficiency surveys do not always signal laboratory testing problems. This is a report of the results of a user's investigation of the proficiency testing flags encountered in our laboratory from three survey programs over a two-year period. The survey programs were administered by the College of American Pathologists, the Centers for Disease Control, and the State of New York. The explanations for the abnormal survey results were classified into six categories: possible analytic measurement problem (28%), clerical error in transcription or completion of forms (16%), inappropriate survey criteria (17%), specimen problem (11%), agency amended report (5%), and no identifiable cause (23%).