Combined international external quality assessment results of medical laboratory performance and reporting of samples with known antimicrobial resistance

Background Reporting on the presence of antimicrobial resistance is of considerable concern both for individual patient care and for understanding the underlying health status within the community at large. Antimicrobial resistance is solely dependent upon clinical laboratory detection and thus can be impacted upon by the quality and competence of medical laboratories. Proficiency testing or external quality assessment (PT/EQA) is the international standard for the direct measurement of medical laboratory performance on critical testing. Methods An international, intercontinental collaborative retrospective study of medical laboratory performance in antibiotic resistance was performed by the Microbiology Working Group (MWG) of the European Organisation for External Quality Assurance for Laboratory Medicine (EQALM) with particular examination of laboratory performance on the testing and reporting of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and carbapenem-resistant Enterobacteriaceae (CRE). Results The results of 1880 medical laboratories were compiled. Strictly accurate reporting of isolates as resistant occurred with MRSA 96.9%, with VRE 91.3% and with CRE 93.1% of the time. On the other hand, very major errors (reporting of false susceptibility) were observed with 2.2% of MRSA and 2.4% of VRE and 0.8% of CRE. Major errors (false resistance) were reported for vancomycin susceptibility testing for MRSA at a rate of 0.6%. Conclusions Depending on how clinical physicians read and understand microbiology susceptibility reports, proficient acceptable results were reported either between 91% and 94% of the time, or between 97% and 100%. While very major errors are infrequently reported, they were found in all regions and could potentially cause poor treatment decisions by clinicians. A collective analysis of multi-program PT/EQA information can provide valuable insights into the testing and reporting practices of medical laboratories.