To reduce the risk of drug-induced haemolysis, all patients should be tested for glucose-6-phosphate dehydrogenase (G6PD) deficiency (G6PDd) prior to prescribing primaquine (PQ)-based radical cure ...for the treatment of vivax malaria. This systematic review and individual patient meta-analysis assessed the utility of a qualitative lateral flow assay from Access Bio/CareStart (Somerset, NJ) (CareStart Screening test for G6PD deficiency) for the diagnosis of G6PDd compared to the gold standard spectrophotometry (International Prospective Register of Systematic Reviews PROSPERO: CRD42019110994).
Articles published on PubMed between 1 January 2011 and 27 September 2019 were screened. Articles reporting performance of the standard CSG from venous or capillary blood samples collected prospectively and considering spectrophotometry as gold standard (using kits from Trinity Biotech PLC, Wicklow, Ireland) were included. Authors of articles fulfilling the inclusion criteria were contacted to contribute anonymized individual data. Minimal data requested were sex of the participant, CSG result, spectrophotometry result in U/gHb, and haemoglobin (Hb) reading. The adjusted male median (AMM) was calculated per site and defined as 100% G6PD activity. G6PDd was defined as an enzyme activity of less than 30%. Pooled estimates for sensitivity and specificity, unconditional negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were calculated comparing CSG results to spectrophotometry using a random-effects bivariate model. Of 11 eligible published articles, individual data were available from 8 studies, 6 from Southeast Asia, 1 from Africa, and 1 from the Americas. A total of 5,815 individual participant data (IPD) were available, of which 5,777 results (99.3%) were considered for analysis, including data from 3,095 (53.6%) females. Overall, the CSG had a pooled sensitivity of 0.96 (95% CI 0.90-0.99) and a specificity of 0.95 (95% CI 0.92-0.96). When the prevalence of G6PDd was varied from 5% to 30%, the unconditional NPV was 0.99 (95% CI 0.94-1.00), with an LR+ and an LR- of 18.23 (95% CI 13.04-25.48) and 0.05 (95% CI 0.02-0.12), respectively. Performance was significantly better in males compared to females (p = 0.027) but did not differ significantly between samples collected from capillary or venous blood (p = 0.547). Limitations of the study include the lack of wide geographical representation of the included data and that the CSG results were generated under research conditions, and therefore may not reflect performance in routine settings.
The CSG performed well at the 30% threshold. Its high NPV suggests that the test is suitable to guide PQ treatment, and the high LR+ and low LR- render the test suitable to confirm and exclude G6PDd. Further operational studies are needed to confirm the utility of the test in remote endemic settings.
The WHO recommends routine testing of G6PD activity to guide radical cure in patients with Plasmodium vivax malaria. Females may have intermediate G6PD enzyme activity and to date, only complex ...diagnostics are able to reliably identify them. The semi-quantitative G6PD diagnostic "One Step G6PD Test" (Humasis, RoK; "RDT") is a lateral flow assay that can distinguish deficient, intermediate, and normal G6PD status and offers a simpler diagnostic alternative.
G6PD status of participants enrolled in Malinau and Nunukan Regencies and the capital Jakarta was assessed with the RDT, and G6PD activity was measured in duplicate by reference spectrophotometry. The adjusted male median (AMM) of the spectrophotometry measurements was defined as 100% activity; 70% and 30% of the AMM were defined as thresholds for intermediate and deficient G6PD status, respectively. Results were compared to those derived from spectrophotometry at the clinically relevant G6PD activity thresholds of 30% and 70%.
Of the 161 participants enrolled, 10 (6.2%) were G6PD deficient and 12 (7.5%) had intermediate G6PD activity by spectrophotometry. At the 30% threshold, the sensitivity of the RDT was 10.0% (95%CI: 0.3-44.5%) with a specificity of 99.3% (95%CI: 96.4-100.0%); the positive predictive value was 50.0% (95%CI: 1.3-98.7%) and the negative predictive value 94.3% (95%CI: 89.5-97.4%). The corresponding figures at the 70% threshold were 22.7% (95%CI: 7.8-45.4%), 100.0% (95%CI: 97.4-100.0%), 100.0% (95%CI: 47.8-100.0%) and 89.1% (95%CI: 83.1-93.5%), respectively.
While there is a dire need for an easy-to-use, economical, semi-quantitative diagnostic for the point of care, the observed performance of the "One Step G6PD Test" in its current form was insufficient to guide antimalarial treatment.
Patients infected by Plasmodium vivax or Plasmodium ovale suffer repeated clinical attacks without primaquine therapy against latent stages in liver. Primaquine causes seriously threatening acute ...hemolytic anemia in patients having inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency. Access to safe primaquine therapy hinges upon the ability to confirm G6PD normal status. CareStart G6PD, a qualitative G6PD rapid diagnostic test (G6PD RDT) intended for use at point-of-care in impoverished rural settings where most malaria patients live, was evaluated.
This device and the standard qualitative fluorescent spot test (FST) were each compared against the quantitative spectrophotometric assay for G6PD activity as the diagnostic gold standard. The assessment occurred at meso-endemic Panenggo Ede in western Sumba Island in eastern Indonesia, where 610 residents provided venous blood. The G6PD RDT and FST qualitative assessments were performed in the field, whereas the quantitative assay was performed in a research laboratory at Jakarta. The median G6PD activity ≥ 5 U/gHb was 9.7 U/gHb and was considered 100% of normal activity. The prevalence of G6PD deficiency by quantitative assessment (<5 U/gHb) was 7.2%. Applying 30% of normal G6PD activity as the cut-off for qualitative testing, the sensitivity, specificity, positive predictive value, and negative predictive value for G6PD RDT versus FST among males were as follows: 100%, 98.7%, 89%, and 100% versus 91.7%, 92%, 55%, and 99%; P = 0.49, 0.001, 0.004, and 0.24, respectively. These values among females were: 83%, 92.7%, 17%, and 99.7% versus 100%, 92%, 18%, and 100%; P = 1.0, 0.89, 1.0 and 1.0, respectively.
The overall performance of G6PD RDT, especially 100% negative predictive value, demonstrates suitable safety for G6PD screening prior to administering hemolytic drugs like primaquine and many others. Relatively poor diagnostic performance among females due to mosaic G6PD phenotype is an inherent limitation of any current practical screening methodology.
Primaquine is essential for malaria control and elimination since it is the only available drug preventing multiple clinical attacks by relapses of Plasmodium vivax. It is also the only therapy ...against the sexual stages of Plasmodium falciparum infectious to mosquitoes, and is thus useful in preventing malaria transmission. However, the difficulties of diagnosing glucose-6-phosphate dehydrogenase deficiency (G6PDd) greatly hinder primaquine's widespread use, as this common genetic disorder makes patients susceptible to potentially severe and fatal primaquine-induced haemolysis. The risk of such an outcome varies widely among G6PD gene variants.
A literature review was conducted to identify surveys of G6PD variant frequencies among representative population groups. Informative surveys were assembled into two map series: (1) those showing the relative proportions of the different variants among G6PDd individuals; and (2) those showing allele frequencies of G6PD variants based on population surveys without prior G6PDd screening.
Variants showed conspicuous geographic patterns. A limited repertoire of variants was tested for across sub-Saharan Africa, which nevertheless indicated low genetic heterogeneity predominated by the G6PD A(-202A) mutation, though other mutations were common in western Africa. The severe G6PD Mediterranean variant was widespread across western Asia. Further east, a sharp shift in variants was identified, with high variant heterogeneity in the populations of China and the Asia-Pacific where no single variant dominated.
G6PD variants exhibited distinctive region-specific distributions with important primaquine policy implications. Relative homogeneity in the Americas, Africa, and western Asia contrasted sharply with the heterogeneity of variants in China, Southeast Asia and Oceania. These findings will inform rational risk assessments for primaquine in developing public health strategies for malaria control and elimination, and support the future development of regionally targeted policies. The major knowledge gaps highlighted here strongly advocate for further investigation of G6PD variant diversity and their primaquine-sensitivity phenotypes.
Glucose-6-phosphate dehydrogenase (G6PD) is a potentially pathogenic inherited enzyme abnormality and, similar to other human red blood cell polymorphisms, is particularly prevalent in historically ...malaria endemic countries. The spatial extent of Plasmodium vivax malaria overlaps widely with that of G6PD deficiency; unfortunately the only drug licensed for the radical cure and relapse prevention of P. vivax, primaquine, can trigger severe haemolytic anaemia in G6PD deficient individuals. This chapter reviews the past and current data on this unique pharmacogenetic association, which is becoming increasingly important as several nations now consider strategies to eliminate malaria transmission rather than control its clinical burden. G6PD deficiency is a highly variable disorder, in terms of spatial heterogeneity in prevalence and molecular variants, as well as its interactions with P. vivax and primaquine. Consideration of factors including aspects of basic physiology, diagnosis, and clinical triggers of primaquine-induced haemolysis is required to assess the risks and benefits of applying primaquine in various geographic and demographic settings. Given that haemolytically toxic antirelapse drugs will likely be the only therapeutic options for the coming decade, it is clear that we need to understand in depth G6PD deficiency and primaquine-induced haemolysis to determine safe and effective therapeutic strategies to overcome this hurdle and achieve malaria elimination.
Background Plasmodium vivax occurs as a latent infection of liver and a patent infection of red blood cells. Radical cure requires both blood schizontocidal and hypnozoitocidal chemotherapies. The ...hypnozoitocidal therapies available are primaquine and tafenoquine, 8-aminoquinoline drugs that can provoke threatening acute hemolytic anemia in patients having an X-linked G6PD-deficiency. Heterozygous females may screen as G6PD-normal prior to radical cure and go on to experience hemolytic crisis. Methods & findings This study examined G6PD phenotypes in 1928 female subjects living in malarious Sumba Island in eastern Indonesia to ascertain the prevalence of females vulnerable to diagnostic misclassification as G6PD-normal. All 367 (19%) females having <80% G6PD normal activity were genotyped. Among those, 103 (28%) were G6PD wild type, 251 (68·4%) were heterozygous, three (0·8%) were compound heterozygotes, and ten (2·7%) were homozygous deficient. The variants Vanua Lava, Viangchan, Coimbra, Chatham, and Kaiping occurred among them. Below the 70% of normal G6PD activity threshold, just 18 (8%) were G6PD-normal and 214 (92%) were G6PD-deficient. Among the 31 females with <30% G6PD normal activity were all ten homozygotes, all three compound heterozygotes, and just 18 were heterozygotes (7% of those). Conclusions In this population, most G6PD heterozygosity in females occurred between 30% and 70% of normal (69·3%; 183/264). The prevalence of females at risk of G6PD misclassification as normal by qualitative screening was 9·5% (183/1928). Qualitative G6PD screening prior to 8-aminoquinoline therapies against P. vivax may leave one in ten females at risk of hemolytic crisis, which may be remedied by point-of-care quantitative tests.
Malaria elimination will be possible only with serious attempts to address asymptomatic infection and chronic infection by both Plasmodium falciparum and Plasmodium vivax. Currently available drugs ...that can completely clear a human of P. vivax (known as "radical cure"), and that can reduce transmission of malaria parasites, are those in the 8-aminoquinoline drug family, such as primaquine. Unfortunately, people with glucose-6-phosphate dehydrogenase (G6PD) deficiency risk having severe adverse reactions if exposed to these drugs at certain doses. G6PD deficiency is the most common human enzyme defect, affecting approximately 400 million people worldwide.Scaling up radical cure regimens will require testing for G6PD deficiency, at two levels: 1) the individual level to ensure safe case management, and 2) the population level to understand the risk in the local population to guide Plasmodium vivax treatment policy. Several technical and operational knowledge gaps must be addressed to expand access to G6PD deficiency testing and to ensure that a patient's G6PD status is known before deciding to administer an 8-aminoquinoline-based drug.In this report from a stakeholder meeting held in Thailand on October 4 and 5, 2012, G6PD testing in support of radical cure is discussed in detail. The focus is on challenges to the development and evaluation of G6PD diagnostic tests, and on challenges related to the operational aspects of implementing G6PD testing in support of radical cure. The report also describes recommendations for evaluation of diagnostic tests for G6PD deficiency in support of radical cure.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency, an X-linked genetic disorder, is associated with increased risk of jaundice and kernicterus at birth. G6PD deficiency can manifest later in life ...as severe hemolysis, when the individual is exposed to oxidative agents that range from foods such as fava beans, to diseases such as typhoid, to medications such as dapsone, to the curative drugs for Plasmodium (P.) vivax malaria, primaquine and tafenoquine. While routine testing at birth for G6PD deficiency is recommended by the World Health Organization for populations with greater than 5% prevalence of G6PD deficiency and to inform P. vivax case management using primaquine, testing coverage is extremely low. Test coverage is low due to the need to prioritize newborn interventions and the complexity of currently available G6PD tests, especially those used to inform malaria case management. More affordable, accurate, point-of-care (POC) tests for G6PD deficiency are emerging that create an opportunity to extend testing to populations that do not have access to high throughput screening services. Some of these tests are quantitative, which provides an opportunity to address the gender disparity created by the currently available POC qualitative tests that misclassify females with intermediate G6PD activity as normal. In populations where the epidemiology for G6PD deficiency and P. vivax overlap, screening for G6PD deficiency at birth to inform care of the newborn can also be used to inform malaria case management over their lifetime.
Tens of millions of patients diagnosed with vivax malaria cannot safely receive primaquine therapy against repeated attacks caused by activation of dormant liver stages called hypnozoites. Most of ...these patients lack access to screening for glucose-6-phosphate dehydrogenase (G6PD) deficiency, a highly prevalent disorder causing serious acute hemolytic anemia with primaquine therapy. We optimized CuCl inhibition of G6PD in normal red blood cells (RBCs) to assess G6PD diagnostic technologies suited to point of care in the impoverished rural tropics. The most widely applied technology for G6PD screening—the fluorescent spot test (FST)—is impractical in that setting. We evaluated a new point-of-care G6PD screening kit (CareStart G6PD, CSG) against FST using graded CuCl treatments to simulate variable hemizygous states, and varying proportions of CuCl-treated RBC suspensions to simulate variable heterozygous states of G6PD deficiency. In experiments double-blinded to CuCl treatment, technicians reading FST and CSG test (n = 269) classified results as positive or negative for deficiency. At G6PD activity ≤40% of normal (n = 112), CSG test was not inferior to FST in detecting G6PD deficiency ( P = 0.003), with 96% vs 90% ( P = 0.19) sensitivity and 75% and 87% ( P = 0.01) specificity, respectively. The CSG test costs less, requires no specialized equipment, laboratory skills, or cold chain for successful application, and performs as well as the FST standard of care for G6PD screening. Such a device may vastly expand access to primaquine therapy and aid in mitigating the very substantial burden of morbidity and mortality imposed by the hypnozoite reservoir of vivax malaria.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme disorder in the world. Its main function is to generate NADPH that is required for anti-oxidative pathway in the cells ...especially in red blood cells (RBC). G6PD deficiency is X-linked and thus subject to random X-chromosome inactivation in women giving them mosaic expression of G6PD activities in their individual cells. This phenomenon makes it difficult for diagnosis with the currently available G6PD qualitative diagnostic tests. With the rolling out of newly marketed anti-malarial drug tafenoquine, which has a long half-life, screening for G6PD deficiency becomes a necessity where those with < 70% G6PD activity cannot receive this drug. Thus, evidence for a quantitative cut-off for G6PD activity is needed to ensure safe drug administration.
RBC models were developed to analyse the effect of oxidant on RBC oxidative markers namely total glutathione (GSH)and malondialdehyde (MDA). G6PD activity was measured using quantitative assay from Trinity Biotech and was correlated with cytofluorometric assay. RBC from two G6PD heterozygous women with different G6PD activities were also analysed for comparison.
There was a negative correlation between G6PD activity and CuCl concentration and a strong association between G6PD activities and proportion of G6PD normal RBC in CuCl-treated models and in ex vivo RBC. However, in terms of oxidative stress markers analyses, unlike the hypothesis where the lower G6PD activity, the higher MDA and the lower GSH level, the CuCl RBC model showed that in low G6PD activities (10-30%) cells, the MDA level is lower compared to the rest of the models (p < 0.05). The ex vivo models however were in line with the hypothesis, although the result was not significant (p = 0.5). There was a significant difference between RBC with < 60% and those with > 80% G6PD activities in CuCl RBC model, but not in ex vivo RBC (p = 0.5). Genotyping heterozygous subjects showed G6PDViangchan variant with 2.97 U/gHb (33% activity) and 6.58 U/gHb (74% activity).
The GSH analysis has pointed to the 60% G6PD activity cut-off and this data is supportive of the old World Health Organization threshold for intermediate upper limit of 60% G6PD activity. However, there are significant limitations in using MDA assay with CuCl RBC model because the RBC was already stressed due to the copper treatment and thus present a different result when compared to the ex vivo model.
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