Contemporary quality control practices for antimicrobial susceptibility tests: a report from the microbiology portion of the College of American Pathologists (CAP) surveys program.

ABSTRACT

The evaluation of quality control (QC) practices from the College of American Pathologists (CAP) Microbiology Surveys demonstrates a trend away from daily controls similar to that first noted in 1980. Previous recommendations for more relevant cost-containment oriented weekly QC procedures are discussed, and the 1982 CAP Surveys statistics confirm earlier comparability between the daily and weekly QC participant groups. Each QC practice subgroup (daily or weekly) had nearly identical mean disk inhibitory zone diameters, and the performance accuracy on two 1982 challenge strains were very similar. Generally, disk zone diameter from those laboratories using weekly QC were smaller, but the frequency of minor and major (false-resistant) errors was only slightly increased. The authors recommend the conversion to weekly QC of disk or dilution antimicrobial susceptibility tests after an acceptable daily QC performance has been established (See criteria in discussion).