Comparison of quantitative and qualitative tests for glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase deficiency detection using fluorocytometric assay: Evaluation after 1 year of clinical implementation

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common enzymopathy that affects red blood cells (RBCs) and renders them susceptible to oxidative stress. G6PD deficiency can cause hemolytic anemia, especially after exposure to certain drugs or infections. The diagnosis of G6PD deficiency is usually based on spectrophotometric measurement of enzyme activity, but this method has limitations in heterozygous females and in patients with other hematological disorders. In this study, we evaluated the use of flow cytometry as an alternative method for detecting G6PD deficiency in 514 samples (265 females and 249 males) from a clinical laboratory. We compared the results of flow cytometry with those of spectrophotometry and molecular analysis, and assessed the performance of flow cytometry in different subgroups of patients. We found that flow cytometry was able to identify G6PD deficiency in most cases, with high sensitivity and specificity. Flow cytometry also allowed the quantification of the percentage of G6PD-deficient RBCs, which varied among heterozygous females due to X-chromosome inactivation. Moreover, flow cytometry detected several cases of G6PD deficiency that were missed by spectrophotometry, especially in heterozygous females with normal or subnormal enzyme activity. However, flow cytometry also showed some false negative results, mainly in patients with sickle cell disease. Therefore, flow cytometry is a reliable and efficient tool for screening G6PD deficiency, but some precautions should be taken in interpreting the results in patients with other hematological conditions.

Unexpected Rasburicase-Induced Hemolysis in a Patient With Normal Glucose-6-Phosphate Dehydrogenase Activity

Tumor lysis syndrome (TLS) presents significant challenges in oncology, primarily due to metabolic complications such as hyperuricemia, which can lead to acute kidney injury. Rasburicase, a recombinant urate oxidase, is frequently employed to manage hyperuricemia in TLS patients. However, its use is an absolute contraindication in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to the risk of hemolysis. In this case, the patient developed hemolytic anemia post-rasburicase administration even though she had normal G6PD activity, which was confirmed on two separate occasions, including during an acute episode and 3 months later. This case is unique as it documents hemolytic anemia induced by rasburicase in a patient without G6PD deficiency, challenging current understandings of the drug's safety profile. It suggests the need for caution and thorough screening before rasburicase use, even in patients considered low risk for G6PD deficiency. The report highlights the importance of close monitoring for adverse effects and the potential for alternative mechanisms of rasburicase-induced hemolysis.

Field evaluation of a novel semi-quantitative point-of-care diagnostic for G6PD deficiency in Indonesia

BACKGROUND

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.

METHODS

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%.

RESULTS

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.

CONCLUSION

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.

Epidemiology of Glucose-6-Phosphate Dehydrogenase Deficiency in Arab Countries: Insights from a Systematic Review

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common metabolic disorder affecting more than 400 million individuals worldwide. Being an X-linked disorder, the disease is more common among males than females. Various Arab countries estimated the prevalence of G6PD deficiency; however, findings from different countries have not been synthesized collectively. Hence, a systematic review was undertaken to synthesize the findings on the epidemiology of G6PD deficiency in all Arab countries. We performed an electronic systematic literature search based on the eligibility criteria using databases, including MEDLINE, Embase, and CINHAL. The studies included in the review were primary and original research studies assessing the prevalence or incidence, risk factors, or determinants of G6PD deficiency, and published in the English language in a peer-reviewed scientific journal between 2000 and 2022. The systematic review was carried out with the help of an updated PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist. After the screening, 23 full texts were finalized for data extraction. The prevalence of G6PD deficiency ranged from 2 to 31% with a greater burden among high-risk populations like neonates with sickle cell anemia. The determinants included males, family history, consanguineous marriages, and geographic regions, which were all risk factors, except for body weight, which was a protective factor. The prevalence of G6PD deficiency varies across Arab countries, with a higher prevalence in males than females. Different regions of Arab countries need to revisit their screening and diagnostic guidelines to detect G6PD deficiency promptly and prevent unnecessary morbidity and mortality among their communities.

Clinical performance validation of the STANDARD G6PD test: A multi-country pooled analysis

INTRODUCTION

Screening for G6PD deficiency can inform disease management including malaria. Treatment with the antimalarial drugs primaquine and tafenoquine can be guided by point-of-care testing for G6PD deficiency.

METHODS AND FINDINGS

Data from similar clinical studies evaluating the performance of the STANDARD G6PD Test (SD Biosensor, South Korea) conducted in Bangladesh, Brazil, Ethiopia, India, Thailand, the United Kingdom, and the United States were pooled. Test performance was assessed in a retrospective analysis on capillary and venous specimens. All study sites used spectrophotometry for reference G6PD testing, and either the HemoCue or complete blood count for reference hemoglobin measurement. The sensitivity of the STANDARD G6PD Test using the manufacturer thresholds for G6PD deficient and intermediate cases in capillary specimens from 4212 study participants was 100% (95% Confidence Interval (CI): 97.5%-100%) for G6PD deficient cases with <30% activity and 77% (95% CI 66.8%-85.4%) for females with intermediate activity between 30%-70%. Specificity was 98.1% (95% CI 97.6%-98.5%) and 92.8% (95% CI 91.6%-93.9%) for G6PD deficient individuals and intermediate females, respectively. Out of 20 G6PD intermediate females with false normal results, 12 had activity levels >60% on the reference assay. The negative predictive value for females with G6PD activity >60% was 99.6% (95% CI 99.1%-99.8%) on capillary specimens. Sensitivity among 396 P. vivax malaria cases was 100% (69.2%-100.0%) for both deficient and intermediate cases. Across the full dataset, 37% of those classified as G6PD deficient or intermediate resulted from true normal cases. Despite this, over 95% of cases would receive correct treatment with primaquine, over 87% of cases would receive correct treatment with tafenoquine, and no true G6PD deficient cases would be treated inappropriately based on the result of the STANDARD G6PD Test.

CONCLUSIONS

The STANDARD G6PD Test enables safe access to drugs which are contraindicated for individuals with G6PD deficiency. Operational considerations will inform test uptake in specific settings.

Performance Comparison Between Conventional Fluorescent Spot Test and Quantitative Assay in Detecting G6PD Deficiency in Neonates

Objectives

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy worldwide. The fluorescent spot test (FST) is the conventional method for screening neonates for G6PD. However, it has limitations and quantitative assays such as the CareStart Biosensor 1 are being increasingly recommended. This study aimed to compare FST and CareStart Bioensor 1 in their ability to detect G6PD levels in neonates.

Methods

This cross-sectional study involved 455 neonates between June and December 2020. Two milliliters of cord blood were analyzed with CareStart Biosensor 1 and dried cord blood spots with FST. Data was recorded and statistically analyzed. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated to determine the performance of FST at specific G6PD cut-off values; Cohen's kappa analysis assessed the agreement between the two methods.

Results

The sensitivity of FST at 30% cut-off G6PD activity level was 91.0%, (95% CI: 57.0-100) and specificity of 97.0% (95% CI: 95.0-98.0). At 60% cut-off, the FST sensitivity sharply declined to 29.0% (95% CI: 19.0-40.0) with a specificity of 100% (95% CI: 98.0-100). The overall prevalence of G6PD deficiency was 5.1% as measured by FST and 17.8% by Biosensor 1 (p < 0.001).

Conclusions

In this study, FST missed a significant proportion of cases of intermediate G6PD levels. FST also misclassified several G6PD intermediate individuals as normal, rendering them susceptible to oxidative stress. Biosensor 1 reported a significantly higher prevalence of G6PD deficiency.

A Review of the Current Status of G6PD Deficiency Testing to Guide Radical Cure Treatment for Vivax Malaria

Plasmodium vivax malaria continues to cause a significant burden of disease in the Asia-Pacific, the Horn of Africa, and the Americas. In addition to schizontocidal treatment, the 8-aminoquinoline drugs are crucial for the complete removal of the parasite from the human host (radical cure). While well tolerated in most recipients, 8-aminoquinolines can cause severe haemolysis in glucose-6-phosphate dehydrogenase (G6PD) deficient patients. G6PD deficiency is one of the most common enzymopathies worldwide; therefore, the WHO recommends routine testing to guide 8-aminoquinoline based treatment for vivax malaria whenever possible. In practice, this is not yet implemented in most malaria endemic countries. This review provides an update of the characteristics of the most used G6PD diagnostics. We describe the current state of policy and implementation of routine point-of-care G6PD testing in malaria endemic countries and highlight key knowledge gaps that hinder broader implementation. Identified challenges include optimal training of health facility staff on point-of-care diagnostics, quality control of novel G6PD diagnostics, and culturally appropriate information and communication with affected communities around G6PD deficiency and implications for treatment.

Glucose-6-Phosphate Dehydrogenase (G6PD) Measurement Using Biosensors by Community-Based Village Malaria Workers and Hospital Laboratory Staff in Cambodia: A Quantitative Study

Vivax malaria can relapse after an initial infection due to dormant liver stages of the parasite. Radical cure can prevent relapses but requires the measurement of glucose-6-phosphate dehydrogenase enzyme (G6PD) activity to identify G6PD-deficient patients at risk of drug-induced haemolysis. In the absence of reliable G6PD testing, vivax patients are denied radical curative treatment in many places, including rural Cambodia. A novel Biosensor, 'G6PD Standard' (SD Biosensor, Republic of Korea; Biosensor), can measure G6PD activity at the point of care. The objectives of this study were to compare the G6PD activity readings using Biosensors by village malaria workers (VMWs) and hospital-based laboratory technicians (LTs), and to compare the G6PD deficiency categorization recommended by the Biosensor manufacturer with categories derived from a locally estimated adjusted male median (AMM) in Kravanh district, Cambodia. Participants were enrolled between 2021 and 2022 in western Cambodia. Each of the 28 VMWs and 5 LTs received a Biosensor and standardized training on its use. The G6PD activities of febrile patients identified in the community were measured by VMWs; in a subset, a second reading was done by LTs. All participants were tested for malaria by rapid diagnostic test (RDT). The adjusted male median (AMM) was calculated from all RDT-negative participants and defined as 100% G6PD activity. VMWs measured activities in 1344 participants. Of that total, 1327 (98.7%) readings were included in the analysis, and 68 of these had a positive RDT result. We calculated 100% activity as 6.4 U/gHb (interquartile range: 4.5 to 7.8); 9.9% (124/1259) of RDT-negative participants had G6PD activities below 30%, 15.2% (191/1259) had activities between 30% and 70%, and 75.0% (944/1259) had activities greater than 70%. Repeat measurements among 114 participants showed a significant correlation of G6PD readings (rs = 0.784, p < 0.001) between VMWs and LTs. Based on the manufacturer's recommendations, 285 participants (21.5%) had less than 30% activity; however, based on the AMM, 132 participants (10.0%) had less than 30% activity. The G6PD measurements by VMWs and LTs were similar. With the provisions of training, supervision, and monitoring, VMWs could play an important role in the management of vivax malaria, which is critical for the rapid elimination of malaria regionally. Definitions of deficiency based on the manufacturer's recommendations and the population-specific AMM differed significantly, which may warrant revision of these recommendations.

Glucose 6 Phosphate Dehydrogenase (G6PD) quantitation using biosensors at the point of first contact: a mixed method study in Cambodia

BACKGROUND

Quantitative measurement of Glucose-6-Phosphate Dehydrogenase (G6PD) enzyme activity is critical to decide on appropriate treatment and provision of radical cure regimens for vivax malaria. Biosensors are point-of-care semi-quantitative analysers that measure G6PD enzyme activity. The main objective of this study was to evaluate the operational aspects of biosensor deployment in the hands of village malaria workers (VMWs) in Cambodia over a year.

METHODS

Following initial orientation and training at Kravanh Referral Hospital, each VMW (n = 28) and laboratory technician (n = 5) was provided a biosensor (STANDARD SD Biosensor, Republic of Korea) with supplies for routine use. Over the next 12 months VMWs convened every month for refresher training, to collect supplies, and to recalibrate and test their biosensors. A quantitative self-administered questionnaire was used to assess the skills necessary to use the biosensor after the initial training. Subsequently, VMWs were visited at their location of work for field observation and evaluation using an observer-administered questionnaire. All quantitative questionnaire-based data were analysed descriptively. Semi-structured interviews (SSIs) were conducted among all participants to explore their experience and practicalities of using the biosensor in the field. SSIs were transcribed and translated into English and underwent thematic analysis.

RESULTS

A total of 33 participants completed the training and subsequently used the biosensor in the community. Quantitative assessments demonstrated progressive improvement in skills using the biosensor. VMWs expressed confidence and enthusiasm to use biosensors in their routine work. Providing G6PD testing at the point of first contact avoids a multitude of barriers patients have to overcome when travelling to health centres for G6PD testing and radical cure. Deploying biosensors in routine work of VMWs was also considered an opportunity to expand and strengthen the role of VMWs as health care providers in the community. VMWs reported practical concerns related to the use of biosensor such as difficulty in using two pipettes, difficulty in extracting the code chip from the machine, and the narrow base of buffer tube.

CONCLUSIONS

VMWs considered the biosensor a practical and beneficial tool in their routine work. Providing VMWs with biosensors can be considered when followed by appropriate training and regular supervision. Providing community management of vivax malaria at the point of first contact could be key for elimination.

Cord Platelet Count of Full-Term Neonates in Relation to ABO Incompatibility and Glucose-6-Phosphate Dehydrogenase Levels: A Retrospective Cohort Study

Background The immunoglobulin G of mothers with O blood type may sensitize the platelets of their neonates with A (O-A incompatibility) or B (O-B incompatibility) blood type. As the expression and antigenicity of the B antigen on platelets is less than that of the A antigens, we have hypothesized that platelet count is higher in the O-B incompatibility group compared to the O-A incompatibility group. There is controversy about whether glucose-6-phosphate dehydrogenase (G6PD) deficiency, without evidence of hemolysis, is associated with a lower platelet count than G6PD-normal. Aim To assess whether platelet count is higher in the O-B than in the O-A incompatible neonates and whether it correlates with their G6PD levels. Methods This study was a retrospective cohort study on a sample of 835 healthy neonates born at ≥38 weeks gestation who were either A or B blood types with mothers that carried the blood type O Rh-positive. The platelet count (thousand per microliter) from umbilical cord venous blood (UCVB) was used. A G6PD level of 11.0 units/gram of hemoglobin (U/g Hb) was considered the lower reference limit. G6PD deficiency was defined as a G6PD level of <3.3 U/g Hb in both sexes. Intermediate G6PD deficiency in females was described as a G6PD level of 3.3-8.8 U/g Hb. Results The mean UCVB platelet count was higher in female neonates compared to male neonates (n=389, 283±65 versus n=446, 272±73, p=0.01). The mean UCVB platelet count was higher in the O-B incompatibility group in both male (n=114, 291±82 versus n=103, 266±63) and female neonates (n=83, 303±66 versus n=81, 278±58) with G6PD levels of >8.8 U/g Hb. There was a positive weak correlation between UCVB platelet counts and G6PD levels only in O-B incompatible female neonates (n=176, r=0.23, p=0.002). The partitioning and combined 95% reference intervals (RIs) of the UCVB platelet count were presented. Conclusion The platelet count was higher in the O-B incompatibility group compared to the O-A incompatibility group, but only when the G6PD level was >8.8 U/g Hb. A correlation between UCVB platelet count and G6PD levels was found only among O-B incompatible female neonates. These findings may have an important implication in estimating RIs of the UCVB platelet count, however, they need to be confirmed and explored in future research.

Acute Hemolytic Anemia Caused by G6PD Deficiency in Children in Mayotte: A Frequent and Severe Complication

Severe hemolytic anemia is a rare complication of glucose-6-phosphate dehydrogenase (G6PD) deficiency. It occurs with the Mediterranean (Med) variant corresponding to a class 2 deficiency according to the World Health Organization (WHO) classification, and it correlates with a severe deficiency in G6PD activity. In Mayotte, the majority of patients have the African (A-) variant as a WHO class 3 deficiency. Yet we have observed numerous cases of severe hemolytic anemia defined by a hemoglobin level of <6 g/dL. In this study, we aimed to describe the epidemiological, clinical, and biological features as well as the treatment modalities of children presenting with a severe hemolytic crisis secondary to G6PD deficiency in Mayotte. The secondary objective was to study the disease genotype when this information was available. Between April 2013 and September 2020, 73 children presented with severe anemia because of G6PD deficiency in Mayotte. The median hemoglobin level during the hemolytic crises was 3.9 g/dL. All of the patients underwent a transfusion and hospitalization. Twenty patients had a disease genotype: 11 had the African mutation and 9 had the Med mutation. Although they are among the most common triggers of G6PD acute hemolytic anemia, drugs were found to not be present and fava bean ingestion was found in only 1 child. One of the specific triggers was traditional medicine, including Acalypha indica . Severe hemolytic crisis in children because of G6PD deficiency is a frequent occurrence in Mayotte. The patients had severe disease symptoms, but the severity did not correlate with the genotype: the African (A-) variant and the Med variant resulted in the same level of disease severity.

Genetic Variants of Glucose-6-Phosphate Dehydrogenase and Their Associated Enzyme Activity: A Systematic Review and Meta-Analysis

Low glucose-6-phosphate dehydrogenase enzyme (G6PD) activity is a key determinant of drug-induced haemolysis. More than 230 clinically relevant genetic variants have been described. We investigated the variation in G6PD activity within and between different genetic variants. In this systematic review, individual patient data from studies reporting G6PD activity measured by spectrophotometry and corresponding the G6PD genotype were pooled (PROSPERO: CRD42020207448). G6PD activity was converted into percent normal activity applying study-specific definitions of 100%. In total, 4320 individuals from 17 studies across 10 countries were included, where 1738 (40.2%) had one of the 24 confirmed G6PD mutations, and 61 observations (3.5%) were identified as outliers. The median activity of the hemi-/homozygotes with A-(c.202G>A/c.376A>G) was 29.0% (range: 1.7% to 76.6%), 10.2% (range: 0.0% to 32.5%) for Mahidol, 16.9% (range 3.3% to 21.3%) for Mediterranean, 9.0% (range: 2.9% to 23.2%) for Vanua Lava, and 7.5% (range: 0.0% to 18.3%) for Viangchan. The median activity in heterozygotes was 72.1% (range: 16.4% to 127.1%) for A-(c.202G>A/c.376A>G), 54.5% (range: 0.0% to 112.8%) for Mahidol, 37.9% (range: 20.7% to 80.5%) for Mediterranean, 53.8% (range: 10.9% to 82.5%) for Vanua Lava, and 52.3% (range: 4.8% to 78.6%) for Viangchan. A total of 99.5% of hemi/homozygotes with the Mahidol mutation and 100% of those with the Mediterranean, Vanua Lava, and Viangchan mutations had <30% activity. For A-(c.202G>A/c.376A>G), 55% of hemi/homozygotes had <30% activity. The G6PD activity for each variant spanned the current classification thresholds used to define clinically relevant categories of enzymatic deficiency.

Sulfhemoglobinemia and methemoglobinemia following acetaminophen overdose

Introduction

Though acetaminophen overdoses are common, acetaminophen induced methemoglobinemia is rare and it is thought to be due to oxidative stress from reactive metabolites. However, few prior cases of sulfhemoglobinemia in the setting of acetaminophen overdose have been reported. We report a case of mixed methemoglobinemia and sulfhemoglobinemia in the setting of a large, isolated acetaminophen ingestion.

Case report

A 30-year-old African American male presented after intentionally ingesting 50 tablets of 500 mg acetaminophen two days prior. He was cyanotic and tachypneic. Peripheral oxygen saturation was 78 % on room air and minimally improved with high-flow oxygen. He was noted to have leukocytosis, thrombocytopenia, anion gap metabolic acidosis with lactic acidemia, acute kidney injury, transaminitis, hyperbilirubinemia, and coagulopathy. Arterial partial pressure of oxygen was normal. Methemoglobin and sulfhemoglobin concentrations were 8.5 % and 5.2 %, respectively. Along with intravenous N-acetylcysteine, methylene blue was administered without clinical improvement. Hemolytic anemia was subsequently noted. Glucose-6- phosphate dehydrogenase (G6PD) deficiency was then confirmed with a quantitative assay and genetic testing. He also received one dose of intravenous metoclopramide. The patient ultimately required eight units of packed red blood cells and several weeks of hemodialysis before discharge on hospital day 43.

Discussion

Acetaminophen is structurally related to compounds known to cause methemoglobinemia and sulfhemoglobinemia. We hypothesize that these dyshemoglobinemias were triggered by acetaminophen-induced oxidative stress. The role of G6PD deficiency in the formation of sulfhemoglobinemia is unclear. Acetaminophen overdoses presenting with methemoglobinemia should prompt concern for underlying G6PD deficiency. Coincidental sulfhemoglobinemia should be considered if the clinical presentation is more severe than the methemoglobin concentration alone would suggest. Use of methylene blue in this case, despite the low measured methemoglobin percentage, which likely triggered hemolytic anemia; methylene blue use in a similar circumstance should be weighed carefully against the risk of harm.

Cut-off values for diagnosis of G6PD deficiency by flow cytometry in Thai population

In heterozygous females, X-inactivation causes a change in glucose-6-phosphate dehydrogenase (G6PD) activity from normal to deficient. Most G6PD screening tests are used to accurately diagnose hemizygous males, but they are less reliable for diagnosing heterozygous females. This study established flow cytometric cut-off values for screening of G6PD deficiency in hemizygous males and heterozygous or homozygous females. We studied 205 (125 females, 80 males) leftover blood samples from quantitative methemoglobin reduction (MR) screening. G6PD gene mutations determined by multiplex amplification refractory mutation system-polymerase chain reaction and direct DNA sequencing were used as the gold standard reference. Accuracy of the test, including the sensitivity, specificity, and positive and negative predictive values, was analyzed using MedCalc software. The optimal cut-off values for classification of %red blood cells with normal G6PD activity or %bright cells into homozygous normal, heterozygous, and homozygous deficiency in females were 85.4–100%, 6.3–85.3%, and 0–6.2%, respectively (sensitivity 93.2%, specificity 100%). The cut-offs for classification into hemizygous normal and hemizygous deficiency in males were 76.5–100% and 0–76.4%, respectively (sensitivity 100%, specificity 96.5%). Flow cytometry can be used to differentiate heterozygous females with intermediate phenotype from homozygous females, but cannot distinguish between heterozygous females with extreme phenotype and homozygous females. By flow cytometry, heterozygous and homozygous deficiency was detected in 29.6% and 3.2% of females, respectively. Among males, hemizygous deficiency was found in 31.3%. Flow cytometry can be used to screen patients with G6PD deficiency, and reliably and efficiently identify heterozygous and homozygous females, and hemizygous males based on cellular G6PD activity.

An International Survey of Glucose-6-Phosphate Dehydrogenase Laboratory Reporting Practices

CONTEXT.—

Glucose-6-phosphate dehydrogenase (G6PD) activity is used in the evaluation of hemolysis risk in patients being assessed for G6PD deficiency. A long-acting 8-aminoquinoline drug (tafenoquine) used in malaria treatment is contraindicated in patients with G6PD deficiency (<70% normal G6PD activity). The current state of G6PD reporting practices to support clinical eligibility assessment is poorly understood.

OBJECTIVE.—

To assess clinical laboratory reporting practices for G6PD testing.

DESIGN.—

In October 2019 and October 2020, voluntary questionnaires were distributed to 327 and 324 laboratories participating in the College of American Pathologists G6PD proficiency testing (PT).

RESULTS.—

Two hundred fifty-seven and 119 laboratories responded to the 2019 and 2020 questionnaires, respectively. Few laboratories have received clinical questions about average normal G6PD activity (US/Canada, 2.0% [3 of 149]; international, 8.4% [9 of 107]), whereas slightly more have determined the average normal G6PD activity for their own assay and patient populations (US/Canada, 6.7% [10 of 149]; international, 19.4% [21 of 108]). Few laboratories report G6PD activity in percent of normal format (US/Canada, 2.7% [4 of 149]; international, 8.3% [9 of 108]). The most common unit of measurement in use for quantitative G6PD reporting is unit per gram of hemoglobin. Reference intervals vary based on assay, reaction temperature, and participant laboratory and demonstrate moderate correlation (r = .46-.51) to G6PD activity measured from a "normal" PT challenge specimen. Nearly half of participants (47.8% [85 of 178]) categorized a quantitatively "intermediate" G6PD PT challenge as "normal" when using qualitative assays.

CONCLUSIONS.—

Percent of normal G6PD activity reporting would facilitate patient eligibility assessment for drugs, such as tafenoquine. Quantitative assays are better able to differentiate "intermediate" specimens than qualitative assays.

Prevalence of chronic conditions in Syrian refugees to Ottawa

OBJECTIVE

To study the prevalence of chronic conditions (ie, anemia, glucose-6-phosphate dehydrogenase [G6PD] deficiency, hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, and tobacco use) in Syrian refugees.

DESIGN

Cross-sectional study. Four primary care health clinics received Syrian refugees from December 2015 to April 2016, and each followed a standard protocol for refugee health assessments.

SETTING

Ottawa, Ont.

PARTICIPANTS

Arabic-speaking Syrian refugees were invited for early primary care health assessment. Most participants arrived in Ottawa from temporary refugee encampments in Lebanon and Jordan between December 2015 and April 2016.

MAIN OUTCOME MEASURES

Following a protocol, family physicians and nurse practitioners systematically documented age, sex, education, hemoglobin level, G6PD status, HBV and HCV infection, and tobacco use.

RESULTS

The study included 669 of the 916 government-assisted refugees, which represents most of the 1087 Syrian refugees to Ottawa: 373 male and 296 female participants. Overall, 28.5% of women and adolescent girls had anemia, and 2.0% of men had G6PD deficiency. The seroprevalence of HBV and HCV infection in the overall population was 0.9% and 0.7%, respectively. Tobacco use was reported in 60.3% of men and 11.7% of women. Overall, alcohol use (3.7%) and other substance use (0.5%) were uncommon.

CONCLUSION

Anemia was a common health problem in women of reproductive age, while the prevalence of chronic HBV and HCV infection was lower than the prevalence in the general Canadian population. Results showed substantial sex differences in tobacco use, with Syrian men using it at a rate much higher than Canadian men and Syrian women. The health assessment did not document chronic conditions affecting dental or mental health.

Genetic Variation of G6PD and CYP2D6: Clinical Implications on the Use of Primaquine for Elimination of Plasmodium vivax

Primaquine, an 8-aminoquinoline, is the only medication approved by the World Health Organization to treat the hypnozoite stage of Plasmodium vivax and P. ovale malaria. Relapse, triggered by activation of dormant hypnozoites in the liver, can occur weeks to years after primary infection, and provides the predominant source of transmission in endemic settings. Hence, primaquine is essential for individual treatment and P. vivax elimination efforts. However, primaquine use is limited by the risk of life-threatening acute hemolytic anemia in glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. More recently, studies have demonstrated decreased efficacy of primaquine due to cytochrome P450 2D6 (CYP2D6) polymorphisms conferring an impaired metabolizer phenotype. Failure of standard primaquine therapy has occurred in individuals with decreased or absent CYP2D6 activity. Both G6PD and CYP2D6 are highly polymorphic genes, with considerable geographic and interethnic variability, adding complexity to primaquine use. Innovative strategies are required to overcome the dual challenge of G6PD deficiency and impaired primaquine metabolism. Further understanding of the pharmacogenetics of primaquine is key to utilizing its full potential. Accurate CYP2D6 genotype-phenotype translation may optimize primaquine dosing strategies for impaired metabolizers and expand its use in a safe, efficacious manner. At an individual level the current challenges with G6PD diagnostics and CYP2D6 testing limit clinical implementation of pharmacogenetics. However, further characterisation of the overlap and spectrum of G6PD and CYP2D6 activity may optimize primaquine use at a population level and facilitate region-specific dosing strategies for mass drug administration. This precision public health approach merits further investigation for P. vivax elimination.

Model-based assessment of the safety of community interventions with primaquine in sub-Saharan Africa

BACKGROUND

Single low-dose primaquine (SLD-PQ) is recommended in combination with artemisinin-based combination therapy to reduce Plasmodium falciparum transmission in areas threatened by artemisinin resistance or aiming for malaria elimination. SLD-PQ may be beneficial in mass drug administration (MDA) campaigns to prevent malaria transmission but uptake is limited by concerns of hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. The aim of this study was to improve the evidence on the safety of MDA with SLD-PQ in a sub-Saharan African setting.

METHODS

A nonlinear mixed-effects model describing the pharmacokinetics and treatment-induced hemolysis of primaquine was developed using data from an adult (n = 16, G6PD deficient) and pediatric study (n = 38, G6PD normal). The relationship between primaquine pharmacokinetics and hemolysis was modeled using an established erythrocyte lifespan model. The safety of MDA with SLD-PQ was explored through Monte Carlo simulations for SLD-PQ at 0.25 or 0.4 mg/kg using baseline data from a Tanzanian setting with detailed information on hemoglobin concentrations and G6PD status.

RESULTS

The predicted reduction in hemoglobin levels following SLD-PQ was small and returned to pre-treatment levels after 25 days. G6PD deficiency (African A- variant) was associated with a 2.5-fold (95% CI 1.2-8.2) larger reduction in hemoglobin levels. In the Tanzanian setting where 43% of the population had at least mild anemia (hemoglobin < 11-13 g/dl depending on age and sex) and 2.73% had severe anemia (hemoglobin < 7-8 g/dl depending on age and sex), an additional 3.7% and 6.0% of the population were predicted to develop at least mild anemia and 0.25% and 0.41% to develop severe anemia after 0.25 and 0.4 mg/kg SLD-PQ, respectively. Children < 5 years of age and women ≥ 15 years of age were found to have a higher chance to have low pre-treatment hemoglobin.

CONCLUSIONS

This study supports the feasibility of MDA with SLD-PQ in a sub-Saharan African setting by predicting small and transient reductions in hemoglobin levels. In a setting where a substantial proportion of the population had low hemoglobin concentrations, our simulations suggest treatment with SLD-PQ would result in small increases in the prevalence of anemia which would most likely be transient.

Reference and point-of-care testing for G6PD deficiency: Blood disorder interference, contrived specimens, and fingerstick equivalence and precision

Certain clinical indications and treatments such as the use of rasburicase in cancer therapy and 8-aminoquinolines for Plasmodium vivax malaria treatment would benefit from a point-of-care test for glucose-6-phosphate dehydrogenase (G6PD) deficiency. Three studies were conducted to evaluate the performance of one such test: the STANDARD^™ G6PD Test (SD BIOSENSOR, South Korea). First, biological interference on the test performance was evaluated in specimens with common blood disorders, including high white blood cell (WBC) counts. Second, the test precision on fingerstick specimens was evaluated against five individuals of each, deficient, intermediate, and normal G6PD activity status. Third, clinical performance of the test was evaluated at three point-of-care settings in the United States. The test performed equivalently to the reference assay in specimens with common blood disorders. High WBC count blood samples resulted in overestimation of G6PD activity in both the reference assay and the STANDARD G6PD Test. The STANDARD G6PD Test showed good precision on multiple fingerstick specimens from the same individual. The same G6PD threshold values (U/g Hb) were applied for a semiquantitative interpretation for fingerstick- and venous-derived results. The sensitivity/specificity values (95% confidence intervals) for the test for G6PD deficiency were 100 (92.3–100.0)/97 (95.2–98.2) and 100 (95.7–100.0)/97.4 (95.7–98.5) for venous and capillary specimens, respectively. The same values for females with intermediate (> 30% to ≤ 70%) G6PD activity were 94.1 (71.3–99.9)/88.2 (83.9–91.7) and 82.4 (56.6–96.2)/87.6(83.3–91.2) for venous and capillary specimens, respectively. The STANDARD G6PD Test enables point-of-care testing for G6PD deficiency.

Rapid quantitative assays for glucose-6-phosphate dehydrogenase (G6PD) and hemoglobin combined on a capillary-driven microfluidic chip

Rapid tests for glucose-6-phosphate dehydrogenase (G6PD) are extremely important for determining G6PD deficiency, a widespread metabolic disorder which triggers hemolytic anemia in response to primaquine and tafenoquine medication, the most effective drugs for the radical cure of malaria caused by Plasmodium parasites. Current point-of-care diagnostic devices for G6PD are either qualitative, do not normalize G6PD activity to the hemoglobin concentration, or are very expensive. In this work we developed a capillary-driven microfluidic chip to perform a quantitative G6PD test and a hemoglobin measurement within 2 minutes and using less than 2 μL of sample. We used a powerful microfluidic module to integrate and resuspend locally the reagents needed for the G6PD assay and controls. We also developed a theoretical model that successfully predicts the enzymatic reactions on-chip, guides on-chip reagent spotting and allows efficient integration of multiple assays in miniaturized formats with only a few nanograms of reagents.

Genotypes and phenotypes of G6PD deficiency among Indonesian females across diagnostic thresholds of G6PD activity guiding safe primaquine therapy of latent malaria

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.

Donor sex, age and ethnicity impact stored red blood cell antioxidant metabolism through mechanisms in part explained by glucose 6-phosphate dehydrogenase levels and activity

Red blood cell storage in the blood bank promotes the progressive accumulation of metabolic alterations that may ultimately impact the erythrocyte capacity to cope with oxidant stressors. However, the metabolic underpinnings of the capacity of RBCs to resist oxidant stress and the potential impact of donor biology on this phenotype are not known. Within the framework of the REDS-III RBC-Omics study, RBCs from 8,502 healthy blood donors were stored for 42 days and tested for their propensity to hemolyze following oxidant stress. A subset of extreme hemolyzers donated a second unit of blood, which was stored for 10, 23, and 42 days and profiled again for oxidative hemolysis and metabolomics (599 samples). Alterations of RBC energy and redox homeostasis were noted in donors with high oxidative hemolysis. RBCs from females, donors over 60 years old, donors of Asian/South Asian race-ethnicity, and RBCs stored in additive solution-3 were each independently characterized by improved antioxidant metabolism compared to, respectively, males, donors under 30 years old, Hispanic and African American race ethnicity donors, and RBCs stored in additive solution-1. Merging metabolomics data with results from an independent GWAS study on the same cohort, we identified metabolic markers of hemolysis and G6PD-deficiency, which were associated with extremes in oxidative hemolysis and dysregulation in NADPH and glutathione-dependent detoxification pathways of oxidized lipids. Donor sex, age, ethnicity, additive solution and G6PD status impact the metabolism of the stored erythrocyte and its susceptibility to hemolysis following oxidative insults.

Evaluation of a flow cytometric test for G6PD-deficient erythrocytes

OBJECTIVE

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, an X-linked recessive disorder, is the commonest erythrocytic enzymopathy worldwide. Reliable diagnosis and severity prediction in G6PD-deficient/heterozygous females remain challenging. A recently developed flow cytometric test for G6PD deficiency has shown promise in precisely identifying deficient females. This paper presents our experiences with this test in a subtropical setting and presents a modification in flow cytometric data acquisition strategy.

METHODS

The methaemoglobin reduction + ferryl Hb generation-based flow cytometric G6PD test was compared with the screening methaemoglobin reduction test (MRT) and confirmatory G6PD enzyme activity assay (EAA) in 20 G6PD-deficient males, 22 G6PD-heterozygous/deficient females and 20 controls. Stained cells were also assessed for bright/dim G6PD activity under a fluorescent microscope.

RESULTS

Flow cytometry separated and quantified %bright cells in heterozygous/deficient females, objectively classifying them into 6 normal (>85% bright cells), 14 intermediate (10-85%) and two G6PD-deficient (<10% bright cells). Concordance with MRT was 89% (55/62 cases) and with EAA was 77% (48/62 cases). Fluorometrically predicted violet laser excitation (405-nm) with signal acquisition in the 425-475 nm region was a technical advancement noted for the first time in this paper.

CONCLUSION

Flow cytometry/fluorescence microscopy represent technically straightforward methods for the detection and quantification of G6PD-deficient erythrocytes. Based on our results, we recommend their application as a first-line investigation to screen females who are prescribed an oxidant drug like primaquine or dapsone.

Diagnostic Practices and Treatment for P. vivax in the InterEthnic Therapeutic Encounter of South-Central Vietnam: A Mixed-Methods Study

Malaria elimination in the Greater Mekong Sub-Region is challenged by a rising proportion of malaria attributable to P. vivax. Primaquine (PQ) is effective in eliminating the parasite's dormant liver stages and can prevent relapsing infections, but it induces severe haemolysis in patients with Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, highlighting the importance of testing enzyme activity prior to treatment. A mixed-method study was conducted in south-central Vietnam to explore the factors that affect acceptability of G6PD testing, treatment-seeking behaviors, and adherence to current regimens. The majority of respondents (75.7%) were unaware of the different parasite species and rather differentiated malaria by perceived severity. People sought a diagnosis if suspected of malaria fever but not if they perceived their fevers as mild. Most respondents agreed to take prescribed medication to treat asymptomatic infection (94.1%) and to continue medication even if they felt better (91.5%). Health professionals did not have G6PD diagnostic tools nor the means to prescribe PQ safely. Adherence to treatment was linked to trust in public providers, who were perceived to make therapeutic decisions in the interest of the patient. Greater focus on providing acceptable ways of assessing G6PD deficiency will be needed to ensure the timely elimination of malaria in Vietnam.

Evaluating Percentage-Based Reporting of Glucose-6-Phosphate Dehydrogenase (G6PD) Enzymatic Activity

OBJECTIVES

The World Health Organization recommends measurement of glucose-6-phosphate dehydrogenase (G6PD) activity before initiation of 8-aminoquinoline therapy. A new drug for malaria prophylaxis and treatment (tafenoquine) is contraindicated in patients with G6PD deficiency or unknown G6PD status given its prolonged half-life. Assessments of percentage of normal G6PD activity using laboratory-specific result distributions are not widely available, making tafenoquine-eligibility decisions potentially challenging.

METHODS

Using an institutional review board-exempt protocol, a data set of quantitative G6PD results was retrieved from a national reference laboratory. G6PD testing was previously performed at 37 °C using an automated enzymatic assay configured on a Roche cobas c501 chemistry analyzer.

RESULTS

Overall, 52,216 results from patients 18 years and older and 6,397 results from patients younger than 18 years were obtained. A modified adjusted male median of 12.7 U/g Hb was derived for adult males in this assay configuration. Result distributions showed higher G6PD activity in neonates.

CONCLUSIONS

Retrospective data analysis can be used to determine laboratory-specific normal G6PD activity values in clinical populations and thus can assist in clinical-eligibility considerations for 8-aminoquinoline treatment.

Point-of-care tests for malaria: speeding up the diagnostics at the bedside and challenges in malaria cases detection

Malaria remains as one of the major public health problems worldwide. About 228 million cases occurred in 2018 only, with Africa bearing about 93% of the cases. Asymptomatic population carrying the various forms of the parasite Plasmodium in endemic areas plays an important role in the spread of the disease. To tackle this battle, more sensitive and precise detection kits for malaria are crucial to better control the number of new malaria cases. In this review, we not only discuss some of the available approaches to rapidly detect new malaria cases in endemic areas but also shed light on parallel problems that may affect the detection of individuals infected with the parasite, covering kelch 13 mutation, glucose 6-phosphate dehydrogenase deficiency, and hemoglobin disorders. Available approaches for malaria detection covered in this review are focused on point-of-care tests, including portable polymerase chain reaction and aptamers.

Determining a critical threshold for G6PD activity below which red blood cell response to oxidative stress is poor

Background

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.

Methods

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.

Results

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).

Conclusions

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.

Efficacy of a Spatial Repellent for Control of Malaria in Indonesia: A Cluster-Randomized Controlled Trial

A cluster-randomized, double-blinded, placebo-controlled trial was conducted to estimate the protective efficacy (PE) of a spatial repellent (SR) against malaria infection in Sumba, Indonesia. Following radical cure in 1,341 children aged ≥ 6 months to ≤ 5 years in 24 clusters, households were given transfluthrin or placebo passive emanators (devices designed to release vaporized chemical). Monthly blood screening and biweekly human-landing mosquito catches were performed during a 10-month baseline (June 2015-March 2016) and a 24-month intervention period (April 2016-April 2018). Screening detected 164 first-time infections and an accumulative total of 459 infections in 667 subjects in placebo-control households, and 134 first-time and 253 accumulative total infections among 665 subjects in active intervention households. The 24-cluster protective effect of 27.7% and 31.3%, for time to first-event and overall (total new) infections, respectively, was not statistically significant. Purportedly, this was due in part to zero to low incidence in some clusters, undermining the ability to detect a protective effect. Subgroup analysis of 19 clusters where at least one infection occurred during baseline showed 33.3% (P-value = 0.083) and 40.9% (P-value = 0.0236, statistically significant at the one-sided 5% significance level) protective effect to first infection and overall infections, respectively. Among 12 moderate- to high-risk clusters, a statistically significant decrease in infection by intervention was detected (60% PE). Primary entomological analysis of impact was inconclusive. Although this study suggests SRs prevent malaria, additional evidence is required to demonstrate the product class provides an operationally feasible and effective means of reducing malaria transmission.

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

Background

Primaquine is an approved radical cure treatment for Plasmodium vivax malaria but treatment can result in life-threatening hemolysis if given to a glucose-6-phosphate dehydrogenase deficient (G6PDd) patient. There is a need for reliable point-of-care G6PD diagnostic tests.

Objectives

To evaluate the performance of the CareStart™ rapid diagnostic test (RDT) in the hands of healthcare workers (HCWs) and village malaria workers (VMWs) in field settings, and to better understand user perceptions about the risks and benefits of PQ treatment guided by RDT results.

Methods

This study enrolled 105 HCWs and VMWs, herein referred to as trainees, who tested 1,543 healthy adult male volunteers from 84 villages in Cambodia. The trainees were instructed on G6PD screening, primaquine case management, and completed pre and post-training questionnaires. Each trainee tested up to 16 volunteers in the field under observation by the study staff.

Results

Out of 1,542 evaluable G6PD volunteers, 251 (16.28%) had quantitative enzymatic activity less than 30% of an adjusted male median (8.30 U/g Hb). There was no significant difference in test sensitivity in detecting G6PDd between trainees (97.21%), expert study staff in the field (98.01%), and in a laboratory setting (95.62%) (p = 0.229); however, test specificity was different for trainees (96.62%), expert study staff in the field (98.14%), and experts in the laboratory (98.99%) (p < 0.001). Negative predictive values were not statistically different for trainees, expert staff, and laboratory testing: 99.44%, 99.61%, and 99.15%, respectively. Knowledge scores increased significantly post-training, with 98.7% willing to prescribe primaquine for P.vivax malaria, an improvement from 40.6% pre-training (p < 0.001).

Conclusion

This study demonstrated ability of medical staff with different background to accurately use CareStart™ RDT to identify G6PDd in male patients, which may enable safer prescribing of primaquine; however, pharmacovigilance is required to address possible G6PDd misclassifications.

Ex Vivo Study of Laban's Role in Decreasing Hemolysis Crisis in G6PD-Deficient Patients

In spite of the vast nutritional and environmental benefits provided by fava bean (Vicia faba), the ingestion of vicine/convicine provokes an acute hemolytic anemia called favism in individuals with a glucose-6-phosphate dehydrogenase (G6PD) deficiency. The elimination of these glycosides is a goal that could be accomplished using different processing methods including bacteriological treatment. Laban as a good source of lactic acid bacteria was tested in an ex vivo assay on human blood samples in order to determine its capacity in decreasing the hemolysis crisis induced by the ingestion of fava beans. Results indicate a significant decrease in human blood cell hemolysis after the treatment of fava beans by Laban. This decrease in hemolysis was also correlated with the G6PD deficiency categorization. The highest hemolysis level (mean: 23.11 ± 0.76%) was observed in samples with G6PD activity between 10 and 30%, while the lowest hemolysis level (mean: 5.75 ± 0.64%) was observed in samples with G6PD activity more than 60%. This decrease was correlated with a high antioxidant capacity of Laban (51.61 ± 1.13% expressed by the percentage inhibition of DPPH radical). The counts of isolates from MRS and M17 culture plates were 6.75 ± 0.095 and 7.91 ± 0.061 log cfu ml^-1, respectively. In conclusion, the synergy between the antioxidant properties of Laban and the possible decrease of vicine and convicine concentrations by lactobacillus found in the fermented dairy products could explain the ability of Laban to reduce the hemolysis crisis ex vivo.

A paper-based biosensor for visual detection of glucose-6-phosphate dehydrogenase from whole blood

Paper-based, colorimetric, visual detection of G6PD from whole blood without need for equipment.

Evaluation of a Novel Quantitative Test for Glucose-6-Phosphate Dehydrogenase Deficiency: Bringing Quantitative Testing for Glucose-6-Phosphate Dehydrogenase Deficiency Closer to the Patient

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, a common genetic blood condition, can result in kernicterus at birth, and later in life as severe hemolysis on exposure to certain infections, foods, and drugs. The unavailability of point-of-care tests for G6PD deficiency is a barrier to routine curative treatment of Plasmodium vivax malaria with 8-aminoquinolines, such as primaquine. Two quantitative reference tests (Trinity Biotech, Bray, Ireland and Pointe Scientific, Canton, MI; Cat No. G7583) and the point-of-care STANDARD^™ G6PD test (SD Biosensor, Suwon, South Korea) were evaluated. The STANDARD G6PD test was evaluated at multiple temperatures, in anticoagulated venous and capillary samples, including 79 G6PD-deficient and 66 intermediate samples and across two laboratories, one in the United States and one in Thailand. The STANDARD test performed equivalently to a reference assay for its ability to diagnose G6PD deficiency (< 30% normal) with a sensitivity of 100% (0.95 confidence interval [CI]: 95.7–100) and specificity of 97% (0.95 CI: 94.5–98.5), and could reliably identify females with less than 70% normal G6PD activity with a sensitivity of 95.5% (0.95 CI: 89.7–98.5) and specificity of 97% (0.95 CI: 94.5–98.6). The STANDARD G6PD product represents an opportunity to diagnose G6PD deficiency equally for males and females in basic clinical laboratories in high- and low-resource settings. This quantitative point-of-care diagnostic test for G6PD deficiency can provide equal access to safe radical cure of P. vivax cases in high- and low-resource settings, for males and females and may support malaria elimination, in countries where P. vivax is endemic.

Short-course primaquine for the radical cure of Plasmodium vivax malaria: a multicentre, randomised, placebo-controlled non-inferiority trial

BACKGROUND

Primaquine is the only widely used drug that prevents Plasmodium vivax malaria relapses, but adherence to the standard 14-day regimen is poor. We aimed to assess the efficacy of a shorter course (7 days) of primaquine for radical cure of vivax malaria.

METHODS

We did a randomised, double-blind, placebo-controlled, non-inferiority trial in eight health-care clinics (two each in Afghanistan, Ethiopia, Indonesia, and Vietnam). Patients (aged ≥6 months) with normal glucose-6-phosphate dehydrogenase (G6PD) and presenting with uncomplicated vivax malaria were enrolled. Patients were given standard blood schizontocidal treatment and randomly assigned (2:2:1) to receive 7 days of supervised primaquine (1·0 mg/kg per day), 14 days of supervised primaquine (0·5 mg/kg per day), or placebo. The primary endpoint was the incidence rate of symptomatic P vivax parasitaemia during the 12-month follow-up period, assessed in the intention-to-treat population. A margin of 0·07 recurrences per person-year was used to establish non-inferiority of the 7-day regimen compared with the 14-day regimen. This trial is registered at ClinicalTrials.gov (NCT01814683).

FINDINGS

Between July 20, 2014, and Nov 25, 2017, 2336 patients were enrolled. The incidence rate of symptomatic recurrent P vivax malaria was 0·18 (95% CI 0·15 to 0·21) recurrences per person-year for 935 patients in the 7-day primaquine group and 0·16 (0·13 to 0·18) for 937 patients in the 14-day primaquine group, a difference of 0·02 (-0·02 to 0·05, p=0·3405). The incidence rate for 464 patients in the placebo group was 0·96 (95% CI 0·83 to 1·08) recurrences per person-year. Potentially drug-related serious adverse events within 42 days of starting treatment were reported in nine (1·0%) of 935 patients in the 7-day group, one (0·1%) of 937 in the 14-day group and none of 464 in the control arm. Four of the serious adverse events were significant haemolysis (three in the 7-day group and one in the 14-day group).

INTERPRETATION

In patients with normal G6PD, 7-day primaquine was well tolerated and non-inferior to 14-day primaquine. The short-course regimen might improve adherence and therefore the effectiveness of primaquine for radical cure of P vivax malaria.

FUNDING

UK Department for International Development, UK Medical Research Council, UK National Institute for Health Research, and the Wellcome Trust through the Joint Global Health Trials Scheme (MR/K007424/1) and the Bill & Melinda Gates Foundation (OPP1054404).

Safety of Single-Dose Primaquine in G6PD-Deficient and G6PD-Normal Males in Mali Without Malaria: An Open-Label, Phase 1, Dose-Adjustment Trial

Background

The World Health Organization recommendation on the use of a single low dose of primaquine (SLD-PQ) to reduce Plasmodium falciparum malaria transmission requires more safety data.

Methods

We conducted an open-label, nonrandomized, dose-adjustment trial of the safety of 3 single doses of primaquine in glucose-6-phosphate dehydrogenase (G6PD)-deficient adult males in Mali, followed by an assessment of safety in G6PD-deficient boys aged 11–17 years and those aged 5–10 years, including G6PD-normal control groups. The primary outcome was the greatest within-person percentage drop in hemoglobin concentration within 10 days after treatment.

Results

Fifty-one participants were included in analysis. G6PD-deficient adult males received 0.40, 0.45, or 0.50 mg/kg of SLD-PQ. G6PD-deficient boys received 0.40 mg/kg of SLD-PQ. There was no evidence of symptomatic hemolysis, and adverse events considered related to study drug (n = 4) were mild. The mean largest within-person percentage change in hemoglobin level between days 0 and 10 was −9.7% (95% confidence interval [CI], −13.5% to −5.90%) in G6PD-deficient adults receiving 0.50 mg/kg of SLD-PQ, −11.5% (95% CI, −16.1% to −6.96%) in G6PD-deficient boys aged 11–17 years, and −9.61% (95% CI, −7.59% to −13.9%) in G6PD-deficient boys aged 5–10 years. The lowest hemoglobin concentration at any point during the study was 92 g/L.

Conclusion

SLD-PQ doses between 0.40 and 0.50 mg/kg were well tolerated in G6PD-deficient males in Mali.

Clinical Trials Registration

NCT02535767.

Addressing the gender-knowledge gap in glucose-6-phosphate dehydrogenase deficiency: challenges and opportunities

Glucose-6-phosphate dehyrdgoenase (G6PD) deficiency is a common X-linked genetic trait, with an associated enzyme phenotype, whereby males are either G6PD deficient or normal, but females exhibit a broader range of G6PD deficiencies, ranging from severe deficiency to normal. Heterozygous females typically have intermediate G6PD activity. G6PD deficiency has implications for the safe treatment for Plasmodium vivax malaria. Individuals with this deficiency are at greater risk of serious adverse events following treatment with the only curative class of anti-malarials, 8-aminoquinolines, such as primaquine. Quantitative diagnostic tests for G6PD deficiency are complex and require sophisticated laboratories. The commonly used qualitative tests, do not discriminate intermediate G6PD activities. This has resulted in poor understanding of the epidemiology of G6PD activity in females and its corresponding treatment ramifications. New simple-to-use quantitative tests, and a momentum to eliminate malaria, create an opportunity to address this knowledge gap. While this will require additional resources for clinical studies, adequate operational research, and appropriate pharmacovigilance, the health benefits from this investment go beyond the immediate intervention for which the G6PD status is first diagnosed.

Drug-induced Hemolysis in G6PD Deficiency: an Unusual Presentation of a Common Clinical Condition

Glucose-6-phosphate dehydrogenase (G6PD) deficiency can present a diagnostic dilemma owing to the varying degrees of disease severity and the wide range of precipitating factors. Here, we report a case of a 56-year-old man who presented with signs and symptoms of heart failure and, during the course of treatment, developed intravascular hemolysis. On investigation, he was found to be G6PD deficient. Following discontinuation of the fixed-dose combination of isosorbide dinitrate and hydralazine, the clinical condition of the patient improved, and there were no further episodes of hemolysis. The case highlights the need for a high degree of suspicion of G6PD deficiency in patients with unexplained signs and symptoms of intravascular hemolysis.

G6PD deficiency, primaquine treatment, and risk of haemolysis in malaria-infected patients

BACKGROUND

The incidence of malaria in the Americas has decreased markedly in recent years. Honduras and the other countries of Mesoamerica and the island of Hispaniola have set the goal of eliminating native malaria by the year 2020. To achieve this goal, Honduras has recently approved national regulations to expand the possibilities of a shortened double dose primaquine (PQ) treatment for vivax malaria. Considering this new shortened anti-malarial treatment, the high frequency of G6PDd genotypes in Honduras, and the lack of routinely assessment of the G6PD deficiency status, this study aimed at investigating the potential association between the intake of PQ and haemolysis in malaria-infected G6PDd subjects.

METHODS

This was a prospective cohort and open-label study. Participants with malaria were recruited. Plasmodium vivax infection was treated with 0.25 mg/kg of PQ daily for 14 days. Safety and signs of haemolysis were evaluated by clinical criteria and laboratory values before and during the 3rd and 7th day of PQ treatment. G6PD status was assessed by a rapid test (CareStart™) and two molecular approaches.

RESULTS

Overall 55 participants were enrolled. The frequency of G6PD deficient genotypes was 7/55 (12.7%), where 5/7 (71.4%) were hemizygous A- males and 2/7 (28.6%) heterozygous A- females. Haemoglobin concentrations were compared between G6PD wild type (B) and G6PDd A- subjects, showing a significant difference between the means of both groups in the 3rd and 7th days. Furthermore, a statistically significant difference was evident in the change in haemoglobin concentration between the 3rd day and the 1st day for both genotypes, but there was no statistical difference for the change in haemoglobin concentration between the 7th day and the 1st day. Besides these changes in the haemoglobin concentrations, none of the patients showed signs or symptoms associated with severe haemolysis, and none needed to be admitted to a hospital for further medical attention.

CONCLUSIONS

The findings support that the intake of PQ during 14 days of treatment against vivax malaria is safe in patients with a class III variant of G6PDd. In view of the new national regulations in the shortened treatment of vivax malaria for 7 days, it is advisable to be alert of potential cases of severe haemolysis that could occur among G6PD deficient hemizygous males with a class II mutation such as the Santamaria variant, previously reported in the country.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency in Ethiopia: absence of common African and Mediterranean allelic variants in a nationwide study

BACKGROUND

Building on the declining trend of malaria in Ethiopia, the Federal Ministry of Health aims to eliminate malaria by 2030. As Plasmodium falciparum and Plasmodium vivax are co-endemic in Ethiopia, the use of primaquine is indicated for both transmission interruption and radical cure, respectively. However, the limited knowledge of the local prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency and its associated variants has hindered the use of primaquine.

METHODS

Some 11,138 dried blood spot (DBS) samples were collected in 2011 as part of a national, household Malaria Indicator Survey, a multi-stage nationally representative survey of all malaria-endemic areas of Ethiopia. A randomly selected sub-set of 1414 DBS samples was successfully genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Considering the geographical position and ethnic mix of the country, three common variants: G6PD*A (A376G), G6PD*A- (G202A) and Mediterranean (C563T) were investigated.

RESULTS

Of the 1998 randomly selected individuals, 1429 (71.5%) DBS samples were genotyped and merged to the database, of which 53.5% were from females. G6PD*A (A376G) was the only genotype detected. No sample was positive for either G6PD*A- (G202A) or Mediterranean (C563T) variants. The prevalence of G6PD*A (A376G) was 8.9% [95% confidence interval (CI) 6.7-11.2] ranging from 12.2% in the Southern Nations, Nationalities and Peoples' (95% CI 5.7-18.7) to none in Dire Dawa/Harari Region.

CONCLUSION

The common G6PD*A- (G202A) or Mediterranean (C563T) variants were not observed in this nationwide study. The observed G6PD*A (A376G) mutation has little or no clinical significance. These findings supported the adoption of primaquine for P. falciparum transmission interruption and radical cure of P. vivax in Ethiopia. As the presence of other clinically important, less common variants cannot be ruled out, the implementation of radical cure will be accompanied by active haematological and adverse events monitoring in Ethiopia.

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

BACKGROUND

The study aimed to gain first data on the prevalence of G6PD enzyme deficiency measured by spectrophotometry and associated genetic variants in Jimma and surroundings, Ethiopia. The area is a Plasmodium vivax endemic region, but 8-aminoquinolines such as primaquine are not recommended as G6PD testing is not available.

METHODS

Healthy volunteers were recruited at Jimma University, Ethiopia. Enzyme activity was tested by spectrophotometry at the University of Ulm, Germany. A G6PD RDT (Binax NOW^® G6PD, Alere, USA) was additionally performed. The G6PD gene was analysed for polymorphisms in a sub-population. Tests for haemoglobinopathies and the presence of malaria parasites were conducted.

RESULTS

No severe or moderate (cut-off 60%) G6PD deficiency was found in 206 volunteers. Median male activity was 6.1 U/g Hb. Eleven participants (5.4%) showed activities between 70 and 80%. No haemoglobinopathy was detected. None of the subjects showed asymptomatic parasitaemia. One G6PD-A+ variant (A376G) and one new non-synonymous mutation (G445A) were found.

CONCLUSIONS

As the prevalence of G6PD deficiency seems low in this area, the use of 8-aminoquinolines should be encouraged. However, reliable G6PD testing methods have to be implemented and safe cut-off levels need to be defined.

Comparison of glucose-6 phosphate dehydrogenase status by fluorescent spot test and rapid diagnostic test in Lao PDR and Cambodia

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy worldwide. Primaquine is the only licensed drug that effectively removes Plasmodium vivax hypnozoites from the human host and prevents relapse. While well tolerated by most recipients, primaquine can cause haemolysis in G6PD deficient individuals and is, therefore, underused. Rapid diagnostic tests (RDTs) could permit ascertainment of G6PD status outside of laboratory settings and hence safe treatment in remote areas. The performance of the fluorescent spot test (Trinity, Ireland; FST) and a G6PD RDT (Carestart, USA) against spectrophotometry were assessed.

METHODS

Participants were enrolled during cross-sectional surveys in Laos and by purposive sampling in Cambodia. FST and RDT were performed during village surveys and 3 mL of venous blood was collected for subsequent G6PD measurement by spectrophotometry.

RESULTS

A total of 757 participants were enrolled in Laos and 505 in Cambodia. FST and RDT performed best at 30% cut-off activity and performed significantly better in Laos than in Cambodia. When defining intermediate results as G6PD deficient, the FST had a sensitivity of 100% (95%CI 90-100) and specificity of 90% (95%CI 87.7-92.2) in Laos and sensitivity of 98% (94.1-99.6) and specificity of 71% (95%CI 66-76) in Cambodia (p < 0.001). The RDT had sensitivity and specificity of 100% (95%CI 90-100) and 99% (95%CI 97-99) in Laos and sensitivity and specificity of 91% (86-96) and 93% (90-95) in Cambodia (p < 0.001). The RDT performed significantly better (all p < 0.05) than the FST when intermediate FST results were defined as G6PD deficient.

CONCLUSION

The interpretation of RDT results requires some training but is a good alternative to the FST. Trial registration clinicaltrials.gov; NCT01872702; 06/27/2013; https://clinicaltrials.gov/ct2/show/NCT01872702.

Implications of current therapeutic restrictions for primaquine and tafenoquine in the radical cure of vivax malaria

Background

The 8-aminoquinoline antimalarials, the only drugs which prevent relapse of vivax and ovale malaria (radical cure), cause dose-dependent oxidant haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Patients with <30% and <70% of normal G6PD activity are not given standard regimens of primaquine and tafenoquine, respectively. Both drugs are currently considered contraindicated in pregnant and lactating women.

Methods

Quantitative G6PD enzyme activity data from 5198 individuals were used to estimate the proportions of heterozygous females who would be ineligible for treatment at the 30% and 70% activity thresholds, and the relationship with the severity of the deficiency. This was used to construct a simple model relating allele frequency in males to the potential population coverage of tafenoquine and primaquine under current prescribing restrictions.

Findings

Independent of G6PD deficiency, the current pregnancy and lactation restrictions will exclude ~13% of females from radical cure treatment. This could be reduced to ~4% if 8-aminoquinolines can be prescribed to women breast-feeding infants older than 1 month. At a 30% activity threshold, approximately 8–19% of G6PD heterozygous women are ineligible for primaquine treatment; at a 70% threshold, 50–70% of heterozygous women and approximately 5% of G6PD wild type individuals are ineligible for tafenoquine treatment. Thus, overall in areas where the G6PDd allele frequency is >10% more than 15% of men and more than 25% of women would be unable to receive tafenoquine. In vivax malaria infected patients these proportions will be lowered by any protective effect against P. vivax conferred by G6PD deficiency.

Conclusion

If tafenoquine is deployed for radical cure, primaquine will still be needed to obtain high population coverage. Better radical cure antimalarial regimens are needed.

More than half of the malaria outside of Sub-Saharan Africa is caused by the parasite Plasmodium vivax which is characterised by multiple relapses of malaria from parasites which persist in the liver. The only drugs which prevent these relapses (radical cure) are the 8-aminoquinolines primaquine and tafenoquine, and they both cause haemolytic anaemia in G6PD deficiency, the most common enzymopathy of man. Neither can currently be prescribed in pregnancy or lactation. Tafenoquine is given as a single dose regimen and is a significant advance over primaquine (recommended as a 14 day regimen). However, a greater number of individuals, mostly females, will be ineligible for tafenoquine treatment due to a tighter restriction on the minimum G6PD enzyme activity considered safe for use of the drug. Using enzyme activity data from over 5000 individuals, we estimate the proportions ineligible due to G6PD deficiency as a function of the deficient allele prevalence. Adding this to simple estimates of pregnancy and lactation, we estimate the proportions of populations who cannot receive either tafenoquine or primaquine radical cure. For the elimination of vivax malaria in areas with a high prevalence of G6PD deficiency, then if tafenoquine is deployed primaquine will still be needed, so better regimens should be developed.

STARD-rapid screening for the 6 most common G6PD gene mutations in the Chinese population using the amplification refractory mutation system combined with melting curve analysis

Dot-blot hybridization and high-resolution melting curve methods are used to detect G6PD gene mutations; however, the performance and throughput limitations of these methods hinder their use for screening large populations. For simple screening, we developed a novel approach called "Amplification Refractory Mutation System combined with Melting Curve Analysis (ARMS-MC)," which enables rapid and batch-based detection of the 6 most common G6PD mutations.In this method, we established 4 PCR reaction systems that can be used to detect the 6 most common G6PD mutations (c.95A>G, c.392G>T, c.871G>A, c.1024C>T, c.1376G>T, and c.1388G>A) in the Chinese population.The ARMS-MC method was evaluated with 174 cases of clinical G6PD-deficient samples, and the results were verified by direct sequencing at G6PD gene exons. The results showed that 170 samples had ≥1 of the 6 mutations, which accounted for 97.70% of all mutations. These results were consistent with the results of direct sequencing with 100% accuracy and specificity. Sequencing validation revealed other mutations in the 4 samples in which no mutation was detected by the ARMS-MC method.ARMS-MC provides a rapid, simple, inexpensive, and accurate screening method for detecting the most common G6PD mutations in Chinese people.

Primaquine-induced haemolysis in females heterozygous for G6PD deficiency

Oxidative agents can cause acute haemolytic anaemia in persons with G6PD deficiency. Understanding the relationship between G6PD genotype and the phenotypic expression of the enzyme deficiency is necessary so that severe haemolysis can be avoided. The patterns of oxidative haemolysis have been well described in G6PD deficient hemizygous males and homozygous females; and haemolysis in the proportionally more numerous heterozygous females has been documented mainly following consumption of fava beans and more recently dapsone. It has long been known that 8-aminoquinolines, notably primaquine and tafenoquine, cause acute haemolysis in G6PD deficiency. To support wider use of primaquine in Plasmodium vivax elimination, more data are needed on the haemolytic consequences of 8-aminoquinolines in G6PD heterozygous females. Two recent studies (in 2017) have provided precisely such data; and the need has emerged for the development of point of care quantitative testing of G6PD activity. Another priority is exploring alternative 8-aminoquinoline dosing regimens that are practical and improve safety in G6PD deficient individuals.

Single low-dose primaquine for blocking transmission of Plasmodium falciparum malaria - a proposed model-derived age-based regimen for sub-Saharan Africa

BACKGROUND

In 2012, the World Health Organization recommended blocking the transmission of Plasmodium falciparum with single low-dose primaquine (SLDPQ, target dose 0.25 mg base/kg body weight), without testing for glucose-6-phosphate dehydrogenase deficiency (G6PDd), when treating patients with uncomplicated falciparum malaria. We sought to develop an age-based SLDPQ regimen that would be suitable for sub-Saharan Africa.

METHODS

Using data on the anti-infectivity efficacy and tolerability of primaquine (PQ), the epidemiology of anaemia, and the risks of PQ-induced acute haemolytic anaemia (AHA) and clinically significant anaemia (CSA), we prospectively defined therapeutic-dose ranges of 0.15-0.4 mg PQ base/kg for children aged 1-5 years and 0.15-0.5 mg PQ base/kg for individuals aged ≥6 years (therapeutic indices 2.7 and 3.3, respectively). We chose 1.25 mg PQ base for infants aged 6-11 months because they have the highest rate of baseline anaemia and the highest risks of AHA and CSA. We modelled an anthropometric database of 661,979 African individuals aged ≥6 months (549,127 healthy individuals, 28,466 malaria patients and 84,386 individuals with other infections/illnesses) by the Box-Cox transformation power exponential and tested PQ doses of 1-15 mg base, selecting dosing groups based on calculated mg/kg PQ doses.

RESULTS

From the Box-Cox transformation power exponential model, five age categories were selected: (i) 6-11 months (n = 39,886, 6.03%), (ii) 1-5 years (n = 261,036, 45.46%), (iii) 6-9 years (n = 20,770, 3.14%), (iv) 10-14 years (n = 12,155, 1.84%) and (v) ≥15 years (n = 328,132, 49.57%) to receive 1.25, 2.5, 5, 7.5 and 15 mg PQ base for corresponding median (1st and 99th centiles) mg/kg PQ base of: (i) 0.16 (0.12-0.25), (ii) 0.21 (0.13-0.37), (iii) 0.25 (0.16-0.38), (iv) 0.26 (0.15-0.38) and (v) 0.27 (0.17-0.40). The proportions of individuals predicted to receive optimal therapeutic PQ doses were: 73.2 (29,180/39,886), 93.7 (244,537/261,036), 99.6 (20,690/20,770), 99.4 (12,086/12,155) and 99.8% (327,620/328,132), respectively.

CONCLUSIONS

We plan to test the safety of this age-based dosing regimen in a large randomised placebo-controlled trial (ISRCTN11594437) of uncomplicated falciparum malaria in G6PDd African children aged 0.5 - 11 years. If the regimen is safe and demonstrates adequate pharmacokinetics, it should be used to support malaria elimination.

Cytochemical flow analysis of intracellular G6PD and aggregate analysis of mosaic G6PD expression

Background

Medicines that exert oxidative pressure on red blood cells (RBC) can cause severe hemolysis in patients with glucose‐6‐phosphate dehydrogenase (G6PD) deficiency. Due to X‐chromosome inactivation, females heterozygous for G6PD with 1 allele encoding a G6PD‐deficient protein and the other a normal protein produce 2 RBC populations each expressing exclusively 1 allele. The G6PD mosaic is not captured with routine G6PD tests.

Methods

An open‐source software tool for G6PD cytofluorometric data interpretation is described. The tool interprets data in terms of % bright RBC, or cells with normal G6PD activity in specimens collected from 2 geographically and ethnically distinct populations, an African American cohort (USA) and a Karen and Burman ethnic cohort (Thailand) comprising 242 specimens including 89 heterozygous females.

Results

The tool allowed comparison of data across 2 laboratories and both populations. Hemizygous normal or deficient males and homozygous normal or deficient females cluster at narrow % bright cells with mean values of 96%, or 6% (males) and 97%, or 2% (females), respectively. Heterozygous females show a distribution of 10‐85% bright cells and a mean of 50%. The distributions are associated with the severity of the G6PD mutation.

Conclusions

Consistent cytofluorometric G6PD analysis facilitates interlaboratory comparison of cellular G6PD profiles and contributes to understanding primaquine‐associated hemolytic risk.