Methods for the field evaluation of quantitative G6PD diagnostics: a review

Abstract

Individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency are at risk of severe haemolysis following the administration of 8-aminoquinoline compounds. Primaquine is the only widely available 8-aminoquinoline for the radical cure of Plasmodium vivax. Tafenoquine is under development with the potential to simplify treatment regimens, but point-of-care (PoC) tests will be needed to provide quantitative measurement of G6PD activity prior to its administration. There is currently a lack of appropriate G6PD PoC tests, but a number of new tests are in development and are likely to enter the market in the coming years. As these are implemented, they will need to be validated in field studies. This article outlines the technical details for the field evaluation of novel quantitative G6PD diagnostics such as sample handling, reference testing and statistical analysis. Field evaluation is based on the comparison of paired samples, including one sample tested by the new assay at point of care and one sample tested by the gold-standard reference method, UV spectrophotometry in an established laboratory. Samples can be collected as capillary or venous blood; the existing literature suggests that potential differences in capillary or venous blood are unlikely to affect results substantially. The collection and storage of samples is critical to ensure preservation of enzyme activity, it is recommended that samples are stored at 4 °C and testing occurs within 4 days of collection. Test results can be visually presented as scatter plot, Bland–Altman plot, and a histogram of the G6PD activity distribution of the study population. Calculating the adjusted male median allows categorizing results according to G6PD activity to calculate standard performance indicators and to perform receiver operating characteristic (ROC) analysis.

Glucose-6-phosphate dehydrogenase activity measured by spectrophotometry and associated genetic variants from the Oromiya zone, Ethiopia

“…Loss of enzyme activity during the process cannot be excluded. As Ley and colleagues point out, the duration between blood collection and spectrophotometry and the storage conditions in between are the crucial factors to maintain a stable enzyme activity [ 7 ].…”

“…Affecting over 400 million people, it is one of the most common enzyme deficiencies in the world that is probably protective against malaria especially severe malaria outcomes [ 7 ]. G6PD is an essential enzyme in the pentose phosphate pathway assuring normal oxidizing processes in the red blood cells (RBC).…”

Mass drug administrations with dihydroartemisinin-piperaquine and single low dose primaquine to eliminate Plasmodium falciparum have only a transient impact on Plasmodium vivax: Findings from randomised controlled trials

“…Robust and accurate point-of-care tests for the diagnosis of G6PD deficiency could play a pivotal role in the elimination of vivax malaria. A range of new diagnostic tests is currently in development [29,30]. Second, high participation in mass treatment programmes is critical in clearing asymptomatic reservoirs.…”

Evaluation of the CareStart™ glucose-6-phosphate dehydrogenase (G6PD) rapid diagnostic test in the field settings and assessment of perceived risk from primaquine at the community level in Cambodia

“…The reduction in malaria cases observed in Cambodia over the last decade is primarily due to the lower burden of P. falciparum (Pf) malaria [2,6]. Recently, G6PD point-of-care tests have become commercially available but provider training on G6PDd diagnosis and the use of G6PD rapid diagnostic tests (RDTs) at the community level is poorly defined [7]. In order to eliminate Pv by 2025, the goal set by the Cambodian government, the implementation of screening for G6PDd at the community level will be required [8].…”