Analytical quality, performance indices and laboratory service

Faulty data lead to suboptimal diagnostics and decision making unless the f law is known and amenable to correction. However, pure noise (added analyti cal variance) has only minor effects on clinically appropriate indices of d iagnostic performance. This fact is illustrated by an idealized screening p rogramme, using the preventive benefit-to-cost ratio as the index of perfor mance. Further, this article illustrates that the effect of an unnoticed so urce of noise is roughly just twice the effect that the same noise will hav e when its magnitude is known and clinical decision Limits are adjusted acc ordingly. Owing to the small size of these effects, however, it may be prof itable to spend resources on other aspects of good laboratory service, such as timeliness, documentation and interpretative support.