A Longitudinal Assessment of External Quality Assurance Performance of Haematology and Coagulation Analytes at an Academic Laboratory

Abstract

Participation in external quality assurance (EQA) is a requirement of the South African National Accreditation System. The main purpose of EQA is to monitor quality from sample collection to authorizing of results in order to improve laboratory performance. This study evaluated the EQA performance of the haematology and coagulation test parameters on the Royal College of Pathologists of Australasia program from December 2016 to December 2020 at Charlotte Maxeke Johannesburg Academic Hospital. The following tests were assessed from the EQA reports, the full blood count, differential, and reticulocyte (Sysmex XN haematology analysers, Roche Diagnostics, Kobe, Japan); erythrocyte sedimentation rate (StaRRsed, Mechatronics, Zwaag, the Netherlands); and lupus anticoagulant, von Willebrand factor, prothrombin time, international normalised ratio, fibrinogen, activated partial thromboplastin time (aPTT), thrombin time, d-dimer and coagulation factors (STA-R/Max evolution coagulation analysers, Diagnostica Stago, Paris, France). The test performance was determined from analytical quality specification (APS) and/or z-scores. Bias and imprecision were used to calculate sigma (σ) metric scores. Specifications from European Federation of Laboratory Medicine and/or biological variation were applied. The laboratory achieved a satisfactory mean testing score of at least 80% over the 4-year study period. All the haematology and coagulation test parameters evaluated achieved an acceptable APS. The mean z-scores, however, were >2 and unacceptable for the mean cell volume and haematocrit. On investigation, this was attributed to a pre-survey issue. The median σ value was ≥ 6 for white cell count, haemoglobin, aPTT, thrombin time, fibrinogen, and d-dimers. EQA participation assisted the laboratory in maintaining a quality system. Ageing of the analytical platforms with a decline in test performance was not observed during the study period. Six sigma may be a beneficial quality management system tool for haematology laboratories with multiple analysers.