Repeatability and reproducibility of a handheld quantitative G6PD diagnostic

Abstract

Background The introduction of novel short course treatment regimens for the radical cure of Plasmodium vivax requires reliable point-of-care diagnosis that can identify glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. While deficient males can be identified using a qualitative diagnostic test, the genetic make-up of females requires a quantitative measurement. SD Biosensor (Republic of Korea) has developed a handheld quantitative G6PD diagnostic (STANDARD G6PD test), that has approximately 90% accuracy in field studies for identifying individuals with intermediate or severe deficiency. The device can only be considered for routine care if precision of the assay is high. Methods and findings Commercial lyophilised controls (ACS Analytics, USA) with high, intermediate, and low G6PD activities were assessed 20 times on 10 Biosensor devices and compared to spectrophotometry (Pointe Scientific, USA). Each device was then dispatched to one of 10 different laboratories with a standard set of the controls. Each control was tested 40 times at each laboratory by a single user and compared to spectrophotometry results. When tested at one site, the mean coefficient of variation (CV) was 0.111, 0.172 and 0.260 for high, intermediate, and low controls across all devices respectively; combined G6PD Biosensor readings correlated well with spectrophotometry (rs = 0.859, pConclusions Repeatability and inter-laboratory reproducibility of the Biosensor were good; though the device did not reliably discriminate between intermediate and low G6PD activities of the lyophilized specimens. Clinical studies are now required to assess the devices performance in practice. Author summary Novel treatment regimens for the radical cure of P. vivax malaria are more effective than current options but require prior quantitative G6PD testing. The reference method for quantitative G6PD measurement is spectrophotometry but, due to its operational characteristics, is not suitable for routine use. Furthermore, poor inter-laboratory reproducibility of spectrophotometry has prevented quantitative global definitions of G6PD deficiency. SD Biosensor (ROK) have developed a novel handheld “Biosensor” device (G6PD STANDARD), which measures G6PD activity within two minutes and has operational characteristics suited to point of care diagnosis. Reported accuracy of the Biosensor against spectrophotometry is around 90%, but its reproducibility remains unknown. This article reports the reproducibility of the device. Standardized samples were tested in two phases, first by a single user on ten Biosensors and then by ten independent users. All users received a standardized one-hour online training. Measured G6PD activities did not differ significantly across all devices in either phase, demonstrating the capacity to provide user-independent results. If further studies under real life conditions generate comparable results, the Biosensor will allow global cut offs for G6PD deficiency to be defined and will greatly simplify the roll out of novel highly effective radical cure treatment regimens for P. vivax infections.