WHO malaria nucleic acid amplification test external quality assessment scheme: results of eleven distributions over 6 years.

Background: The World Health Organization (WHO) recommends parasite-based diagnosis of malaria before treatment. The use of nucleic-acid amplification (NAAT) for detection of Plasmodium spp. has expanded rapidly in recent years, for epidemiological research globally and clinical care in high-resource settings. Data from NAATs are frequently used to inform policy decisions, so quality control is essential to ensure results are reliable and comparable. Therefore, robust quality control, including an external quality assessment (EQA) scheme targeting malaria NAATs, is essential. The WHO Global Malaria Programme and the UK National External Quality Assessment Service (UK NEQAS) have collaborated since 2017 to implement a global malaria NAAT EQA scheme.

Methods: Panels of specimens containing five major species of human-infecting Plasmodium at various parasite concentrations and negative samples were created in lyophilized blood (LB) and dried blood spot (DBS) formats. Two distributions per year were sent, containing five LB and five DBS specimens. Samples were validated by expert referee laboratories prior to distribution. Between 37 and 51 laboratories participated in each distribution and submitted results online. Participants were scored based on their laboratory's stated capacity to identify Plasmodium species, and individual laboratory reports were sent which included performance comparison with anonymized peers. Change in performance over time was calculated using a generalized mixed model with a logit link function.

Results: Participating laboratories were located in 42 countries. Sample format (DBS or LB) and parasite density were found to significantly affect performance, while referee labs performed better at identifying P. falciparum samples than non-referee labs. Performance of laboratories improved significantly over time, especially for lower density and P. falciparum samples.

Conclusions: Results from the first eleven distributions indicate that the EQA scheme has facilitated improved performance of laboratories over time, highlighting the value of implementing such programmes. EQA schemes are critical to safeguarding the reliability of data and diagnoses, especially in situations where NAAT methodologies and protocols are used. In future, funders should make participation in an EQA scheme a requirement for laboratories, and countries can take initiatives to embed such schemes into their own national assessment programmes.