Evaluation of the Sysmex XN-31 automated analyser for blood donor malaria screening at Malawi Blood Transfusion Services

Abstract

Background and Objectives: Balancing blood supply safety and sufficiency is challenging in malaria-endemic countries where the risk of transfusion-transmitted malaria (TTM) is ever-present. In support of reducing this risk, our study aimed at evaluating the performance of the Sysmex XN-31 analyser in blood donor malaria screening, as compared with current practice in Malawi. Materials and Methods: This prospective observational study was conducted on remnant venous donor blood samples collected at Malawi Blood Transfusion Service donation sites countrywide for routine blood-borne pathogen screening. XN-31 results were compared with routine thick smear malaria microscopy, using expert microscopy (phase 1 and 2) plus qualitative malaria polymerase chain reaction (PCR) (phase 2) to adjudicate discrepancies. Results: XN-31 detected malaria in 614 (11.6%) of 5281 study samples compared with 341 (6.5%) for routine microscopy. Of the 273 discrepant samples, 60 smears (phase 1) could not be retrieved for expert microscopic review. Expert microscopy confirmed the XN-31 positivity in 78.8% (149/189) and 91.7% (22/24) of discrepant samples in phase 1 (n = 4416) and phase 2 (n = 975), respectively, with two cases requiring PCR testing, confirming one each as positive and negative, giving sensitivities of 100% and 75% and specificities of 99.9% and 100%, respectively, for XN-31 and routine microscopy. Conclusion: The automated Sysmex XN-31 analyser's high sensitivity and specificity, ability to detect all Plasmodium species and high throughput with rapid turnaround-time, overcomes many of the limitations of currently available diagnostic tests, making it well-suited for malaria screening of donated blood in malaria-endemic countries in support of TTM risk reduction.