Proficiency testing of serum enzymes based on medical-needs criteria.

Proficiency testing goals for serum enzymes have been set by statistical methods, by the ex cathedra statements of experts, based on the intraindividual variation of healthy people, and based on responses from the users of enzyme data, ie, clinicians in practice. Clinicians consider small changes in serum enzyme values to be medically unimportant. Medical-needs criteria are probably the most relevant in setting proficiency testing goals for enzymes. The enzyme values that most modern clinical analyzers are capable of producing are more precise than appears to be medically necessary. We surveyed clinicians for their perceived needs; based on their responses, we conclude that tight proficiency testing limits for enzyme tests are inappropriate.