Abstract
Safe access to the most effective treatment options for Plasmodium vivaxmalaria are limited by the absence of accurate point-of-care testingto detect glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common human genetic disorder. G6PD-deficient patients are at risk of life-threatening hemolysis when exposed to 8-aminoquinolines, the only class of drugs efficacious against P. vivaxhypnozoites. Until recently, only qualitative tests were available in most settings. These accurately identify patients with severe G6PD deficiency (mostly male) but not patients with intermediate G6PD deficiency (always female).This has led to and reinforced a gap in awareness in clinical practice of the risks and implications of G6PD deficiency in females-who, unlike males, can have a heterozygous genotype for G6PD.Increasing recognition of the need for radical cure of P. vivax, first for patients' health and then for malaria elimination, is driving the development of new point-of-care tests for G6PD deficiency and their accessibility to populations in low-resource settings. The availability of simple, affordable, and accurate point-of-care diagnostics for the precise classification of the three G6PD phenotypes can reduce sex-linked disparities by ensuring safe and effective malaria treatment, providing opportunities to develop supportive counseling to enhance understanding of genetic test results, and improving the detection of all G6PD deficiency phenotypes in newborns and their family members.
Highlights
A new, single-dose radical cure for Plasmodium vivax, tafenoquine has recently received registration in Australia (Kozenis®) and the United States (Krintafel®)
The World Health Organization (WHO) estimates that there were 7.5 million cases of P. vivax in 2017 alone[3], a large proportion of which occurred in populations with high glucose-6-phosphate dehydrogenase (G6PD) deficiency prevalence[4]
For most countries approaching malaria elimination, P. vivax is the main contributor to malaria disease burden, and there is recognition of the need for broader access to radical cure with either the current, standard, 7- to 14-day primaquine course or the new, single-dose tafenoquine, both of which are contraindicated in people with G6PD deficiency[5,6,7]
Summary
A new, single-dose radical cure for Plasmodium vivax, tafenoquine has recently received registration in Australia (Kozenis®) and the United States (Krintafel®). Anticipation of mandatory quantitative G6PD testing to support anti-relapse treatment of P. vivax with tafenoquine has spurred the development of new quantitative point-of-care G6PD diagnostic tests, which only recently have become commercially available These tests demonstrate greater accuracy in identifying G6PD deficiency in females, including those with the intermediate phenotype[43,44]. At a higher level, knowing one’s G6PD status at subsequent clinical visits would allow the patient and clinician to prevent a severe haemolytic crisis by avoiding oxidative medication, or if such a prescription is unavoidable, to closely monitor for signs of haemolysis so interventions could be performed earlier This benefit could expand even further if, through appropriate community sensitisation and genetic counseling, a woman with intermediate G6PD activity seeks G6PD testing for her newborn. Deliberations over cost-benefit trade-offs at the country and district level should include careful consideration of the ethical and equity considerations discussed above
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