The use of a technical questionnaire in laboratory proficiency testing.

As an adjunct to laboratory improvement, a technical questionnaire concerning specific steps of the more commonly employed laboratory procedures was incorporated into three proficiency testing evaluations: syphilis serology, mycobacteriology, and parasitology. This addition to proficiency testing revealed some basic and detrimental procedural deviations which could affect the validity of reported clinical values. These procedural deviations were communicated to the laboratories in an attempt to improve performance.