ABSTRACT
INTRODUCTION: Laboratory quality assurance (QA) includes internal quality control (IQC), external quality assurance (EQA) and quality improvement (QI). EQA identifies quality deviations and training needs. D-dimers are breakdown products of thrombus and results guide various clinical decisions. METHODS: The National Health Laboratory Service (NHLS) in South Africa performs the pathology tests for more than 80% of the population. The NHLS Quality Assurance Department distributed 301 questionnaires to laboratories enquiring about D-dimer testing. Two levels of STAGO® and Siemens® commercial D-dimer assay control material were distributed for analysis and returned results analysed. RESULTS: A total of 64 (21.2%) completed questionnaires were returned and 26 (40.6%) laboratories were performing D-dimers with 25 (97%) subscribing to an EQA scheme. All laboratories reported results in D-dimer units with a negative result cut-off of ≤0.25 mg/L but various testing platforms were in use. All returned interpretations of analyses on the blinded control material were correct. The results were also within the respective reference ranges of the controls apart from three outliers. One laboratory obtained a result on STAGO® pathological control that was above the cut-off of the control reference range but the reason for this error could not be identified. Another obtained results on the STAGO® and on the Siemens® normal controls that were both below the cut-off of the control reference range due to transcription errors. CONCLUSION: The study demonstrated the feasibility of a local EQA scheme for D-dimers based on commercial control material that could mitigate against the cost of international EQA scheme participation.
