Non-invasive detection of bilirubin concentrations during the first week of life in a low-resource setting along the Thailand-Myanmar border.

BACKGROUND: Neonatal hyperbilirubinaemia (NH) is a common problem worldwide and is a cause of morbidity and mortality especially in low-resource settings. METHODS: A study was carried out at Shoklo Malaria Research Unit (SMRU) clinics along the Thailand-Myanmar border to evaluate a non-invasive test for diagnosis of NH in a low-resource setting. Performance of a transcutaneous bilirubinometer Dräger Jaundice Meter JM-105 was assessed against routine capillary serum bilirubin testing (with BR-501 microbilirubinometer) before phototherapy during neonatal care in the first week of life. Results were analysed by direct agreement and by various bilirubin thresholds used in clinical practice. Total serum bilirubin was also measured in cord blood at birth and tested for prediction of hyperbilirubinaemia requiring phototherapy in the first week of life. RESULTS: Between April 2020 and May 2023, 742 neonates born at SMRU facilities were included in the study. A total of 695 neonates provided one to nine capillary blood samples for analysis of serum bilirubin (total 1244 tests) during the first week of life. Performance of transcutaneous bilirubinometer was assessed in 307 neonates who provided 687 paired transcutaneous capillary blood tests. Bilirubin levels were also measured in 738 cord blood samples. Adjusted values of transcutaneous bilirubinometer showed excellent agreement with capillary serum bilirubin concentration (intraclass correlation coefficient=0.923) and high sensitivity (>98%) at all clinical thresholds analysed across 3 years of sampling and multiple users. Concentrations of bilirubin detected in cord blood were not useful in identifying neonates at risk of hyperbilirubinaemia requiring treatment. CONCLUSIONS: The transcutaneous bilirubinometer is a reliable tool to screen neonates and identify those needing confirmatory blood testing. Bilirubin concentrations in cord blood are not predictive of hyperbilirubinaemia in neonates.

Transmission-blocking activities of artesunate, chloroquine, and methylene blue on Plasmodium vivax gametocytes.

Plasmodium vivax is now the main cause of malaria outside Africa. The gametocytocidal effects of antimalarial drugs are important to reduce malaria transmissibility, particularly in low-transmission settings, but they are not well characterized for P. vivax. The transmission-blocking effects of chloroquine, artesunate, and methylene blue on P. vivax gametocytes were assessed. Blood specimens were collected from patients presenting with vivax malaria, incubated with or without the tested drugs, and then fed to mosquitos from a laboratory-adapted colony of Anopheles dirus (a major malaria vector in Southeast Asia). The effects on oocyst and sporozoite development were analyzed under a multi-level Bayesian model accounting for assay variability and the heterogeneity of mosquito Plasmodium infection. Artesunate and methylene blue, but not chloroquine, exhibited potent transmission-blocking effects. Gametocyte exposures to artesunate and methylene blue reduced the mean oocyst count 469-fold (95% CI: 345 to 650) and 1,438-fold (95% CI: 970 to 2,064), respectively. The corresponding estimates for the sporozoite stage were a 148-fold reduction (95% CI: 61 to 470) and a 536-fold reduction (95% CI: 246 to 1,311) in the mean counts, respectively. In contrast, high chloroquine exposures reduced the mean oocyst count only 1.40-fold (95% CI: 1.20 to 1.64) and the mean sporozoite count 1.34-fold (95% CI: 1.12 to 1.66). This suggests that patients with vivax malaria often remain infectious to anopheline mosquitos after treatment with chloroquine. Use of artemisinin combination therapies or immediate initiation of primaquine radical cure should reduce the transmissibility of P. vivax infections.

Prevalence and Risk Factors of Neonatal Hyperbilirubinemia in a Semi-Rural Area of the Democratic Republic of Congo: A Cohort Study.

Neonatal hyperbilirubinemia (NH) is a frequent condition that, if left untreated, can lead to neurological disability and death. We assessed the prevalence of NH and associated neonatal and maternal risk factors in 362 mothers and 365 newborns in a semi-rural area of the Democratic Republic of Congo. In addition, we explored the knowledge and practices of mothers regarding this condition. We collected demographic data, anthropometric data, and obstetric and medical anamneses. We examined newborns at birth and at 24, 48, and 72 hours and measured bilirubin at birth in umbilical cord and capillary blood and thereafter in capillary blood. Hemoglobin, hematocrit, ABO group, Rhesus factor, glucose-6-phosphate dehydrogenase (G6PD) deficiency, Hemoglobin S (HbS), and malaria were assessed in mothers and newborns. Among 296 newborns (all time points available), 5.7% developed NH (95% CI: 3.4-9.0) between 24 and 72 hours according to National Institute for Health and Care Excellence (NICE) UK guidelines. There was a significantly higher risk in newborns with G6PD deficiency (homo- and hemizygous adjusted Odd Ratio [aOR]: 21.0, 95% CI: 4.1-105.9), preterm births (aOR: 6.1, 95% CI: 1.4-26.9), newborns with excessive birth weight loss (aOR: 5.8, 95% CI: 1.4-23.2), and hyperbilirubinemia at birth (aOR: 14.8, 95% CI: 2.7-79.6). Newborns with feto-maternal ABO incompatibility and G6PD deficiency had significantly higher bilirubin at birth than others. More than 60% of mothers had adequate knowledge of NH, but compliance with phototherapy in the absence of symptoms was low. Although risk factors for NH are common in this area, prevalence was not high, suggesting a need for better case definition. Implementation of point-of-care devices for diagnosis and awareness programs on risk prevention could help reduce neonatal morbidity and mortality associated with hyperbilirubinemia in these areas.

Technical evaluation and usability of a quantitative G6PD POC test in cord blood: a mixed-methods study in a low-resource setting.

OBJECTIVES: New point-of-care (POC) quantitative G6PD testing devices developed to provide safe radical cure for Plasmodium vivax malaria may be used to diagnose G6PD deficiency in newborns at risk of severe neonatal hyperbilirubinaemia, improving clinical care, and preventing related morbidity and mortality. METHODS: We conducted a mixed-methods study analysing technical performance and usability of the 'STANDARD G6PD' Biosensor when used by trained midwives on cord blood samples at two rural clinics on the Thailand-Myanmar border. RESULTS: In 307 cord blood samples, the Biosensor had a sensitivity of 1.000 (95% CI: 0.859 to 1.000) and a specificity of 0.993 (95% CI: 0.971 to 0.999) as compared with gold-standard spectrophotometry to diagnose G6PD-deficient newborns using a receiver operating characteristic (ROC) analysis-derived threshold of ≤4.8 IU/gHb. The Biosensor had a sensitivity of 0.727 (95% CI: 0.498 to 0.893) and specificity of 0.933 (95% CI: 0.876 to 0.969) for 30%-70% activity range in girls using ROC analysis-derived range of 4.9-9.9 IU/gHb. These thresholds allowed identification of all G6PD-deficient neonates and 80% of female neonates with intermediate phenotypes.Need of phototherapy treatment for neonatal hyperbilirubinaemia was higher in neonates with deficient and intermediate phenotypes as diagnosed by either reference spectrophotometry or Biosensor.Focus group discussions found high levels of learnability, willingness, satisfaction and suitability for the Biosensor in this setting. The staff valued the capacity of the Biosensor to identify newborns with G6PD deficiency early ('We can know that early, we can counsel the parents about the chances of their children getting jaundice') and at the POC, including in more rural settings ('Because we can know the right result of the G6PD deficiency in a short time, especially for the clinic which does not have a lab'). CONCLUSIONS: The Biosensor is a suitable tool in this resource-constrained setting to identify newborns with abnormal G6PD phenotypes at increased risk of neonatal hyperbilirubinaemia.

Repeatability and reproducibility of a handheld quantitative G6PD diagnostic.

BACKGROUND: The introduction of novel short course treatment regimens for the radical cure of Plasmodium vivax requires reliable point-of-care diagnosis that can identify glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. While deficient males can be identified using a qualitative diagnostic test, the genetic make-up of females requires a quantitative measurement. SD Biosensor (Republic of Korea) has developed a handheld quantitative G6PD diagnostic (STANDARD G6PD test), that has approximately 90% accuracy in field studies for identifying individuals with intermediate or severe deficiency. The device can only be considered for routine care if precision of the assay is high. METHODS AND FINDINGS: Commercial lyophilised controls (ACS Analytics, USA) with high, intermediate, and low G6PD activities were assessed 20 times on 10 Biosensor devices and compared to spectrophotometry (Pointe Scientific, USA). Each device was then dispatched to one of 10 different laboratories with a standard set of the controls. Each control was tested 40 times at each laboratory by a single user and compared to spectrophotometry results. When tested at one site, the mean coefficient of variation (CV) was 0.111, 0.172 and 0.260 for high, intermediate, and low controls across all devices respectively; combined G6PD Biosensor readings correlated well with spectrophotometry (rs = 0.859, p<0.001). When tested in different laboratories, correlation was lower (rs = 0.604, p<0.001) and G6PD activity determined by Biosensor for the low and intermediate controls overlapped. The use of lyophilised human blood samples rather than fresh blood may have affected these findings. Biosensor G6PD readings between sites did not differ significantly (p = 0.436), whereas spectrophotometry readings differed markedly between sites (p<0.001). CONCLUSIONS: Repeatability and inter-laboratory reproducibility of the Biosensor were good; though the device did not reliably discriminate between intermediate and low G6PD activities of the lyophilized specimens. Clinical studies are now required to assess the devices performance in practice.

Contribution of genetic factors to high rates of neonatal hyperbilirubinaemia on the Thailand-Myanmar border.

Very high unconjugated bilirubin plasma concentrations in neonates (neonatal hyperbilirubinaemia; NH) may cause neurologic damage (kernicterus). Both increased red blood cell turn-over and immaturity of hepatic glucuronidation contribute to neonatal hyperbilirubinaemia. The incidence of NH requiring phototherapy during the first week of life on the Thailand-Myanmar border is high (approximately 25%). On the Thailand-Myanmar border we investigated the contribution of genetic risk factors to high bilirubin levels in the first month of life in 1596 neonates enrolled in a prospective observational birth cohort study. Lower gestational age (<38 weeks), mutations in the genes encoding glucose-6-phosphate dehydrogenase (G6PD) and uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A1 were identified as the main independent risk factors for NH in the first week, and for prolonged jaundice in the first month of life. Population attributable risks (PAR%) were 61.7% for lower gestational age, 22.9% for hemi or homozygous and 9.9% for heterozygous G6PD deficiency respectively, and 6.3% for UGT1A1*6 homozygosity. In neonates with an estimated gestational age ≥ 38 weeks, G6PD mutations contributed PARs of 38.1% and 23.6% for "early" (≤ 48 hours) and "late" (49-168 hours) NH respectively. For late NH, the PAR for UGT1A1*6 homozygosity was 7.7%. Maternal excess weight was also a significant risk factor for "early" NH while maternal mutations on the beta-globin gene, prolonged rupture of membranes, large haematomas and neonatal sepsis were risk factors for "late" NH. For prolonged jaundice during the first month of life, G6PD mutations and UGT1A1*6 mutation, together with lower gestational age at birth and presence of haematoma were significant risk factors. In this population, genetic factors contribute considerably to the high risk of NH. Diagnostic tools to identify G6PD deficiency at birth would facilitate early recognition of high risk cases.

Reference spectrophotometric values for glucose-6-phosphate dehydrogenase activity in two-to six-month-old infants on the Thailand-Myanmar border.

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency represents a barrier to the full deployment of anti-malarial drugs for vivax malaria elimination and of first-line antibiotics. Lack of established reference ranges for G6PD activity in breast-fed infants puts them at risk of drug-induced haemolysis and restricts access to safe treatment of their mothers. Methods: The present work was undertaken to establish age-specific G6PD normal values using the gold standard spectrophotometric assay to support the future clinical use of tafenoquine in lactating women and safer antibiotic treatment in infants. Results: Spectrophotometric results collected at the Thai-Myanmar border from 78 healthy infants between the ages of 2 and 6 months showed a trend of decreased enzymatic activity with increasing age (which did not reach statistical significance when comparing 2-3 months old against 4-6 months old infants) and provided a reference normal value of 100% activity for infants 2-6 months old of 10.18IU/gHb. Conclusions: Normal reference G6PD activity in 2-6-month-old infants was approximately 140% of that observed in G6PD normal adults from the same population. Age specific G6PD activity thresholds should be used in paediatric populations to avoid drug-induced haemolysis.

Primaquine and tafenoquine are 8-aminoquinolines used to provide radical cure from dormant stages of malaria vivax; recurrence from dormant malaria parasite causes morbidity and mortality especially in women who are not eligible for treatment while pregnant and breastfeeding. Subjects with glucose-6-phosphate dehydrogenase (G6PD) deficiency are susceptible to dose-dependent drug-induced haemolysis when treated with several drugs including antibiotics and 8-aminoquinolines. G6PD testing is necessary before use of these drugs. Adult normal reference values for G6PD enzymatic activity exist for adults and are used to provide safe radical cure with different regimens of primaquine and tafenoquine. We have collected data in infants to establish normal reference values of G6PD enzymatic activity in infants aged 2-6 months. These results will be used in future to carry out clinical trials where breast-feeding women of a malaria endemic area will be treated with 8-aminoquinolines. Inclusion of mothers and their babies will be based on already established reference values in adult and these newly established values for infants. An added benefit for infants is that age-specific reference values established with this study will be used more widely to provide safer antibiotic treatment.

G6PD deficiency in malaria endemic areas of Nepal.

BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is currently a threat to malaria elimination due to risk of primaquine-induced haemolysis in G6PD deficient individuals. The World Health Organization (WHO) recommends G6PD screening before providing primaquine as a radical treatment against vivax malaria. However, evidence regarding the prevalence and causing mutations of G6PD deficiency in Nepal is scarce. METHODS: A cross-sectional, population-based, prevalence study was carried out from May to October 2016 in 12 malaria-endemic districts of Nepal. The screening survey included 4067 participants whose G6PD status was determined by G6PD Care Start™ rapid diagnostic test and genotyping. RESULTS: The prevalence of G6PD deficiency at the national level was 3.5% (4.1% among males and 2.1% among females). When analysed according to ethnic groups, G6PD deficiency was highest among the Janajati (6.2% overall, 17.6% in Mahatto, 7.7% in Chaudhary and 7.5% in Tharu) and low among Brahman and Chhetri (1.3%). District-wise, prevalence was highest in Banke (7.6%) and Chitwan (6.6%). Coimbra mutation (592 C>T) was found among 75.5% of the G6PD-deficient samples analysed and Mahidol (487 G>A) and Mediterranean (563 C>T) mutations were found in equal proportions in the remaining 24.5%. There was no specific geographic or ethnic distribution for the three mutations. CONCLUSIONS: This study has identified populations with moderate to high prevalence of G6PD deficiency which provides strong evidence supporting the WHO recommendations to screen G6PD deficiency at health facility level before the use of primaquine-based radical curative regimen for Plasmodium vivax.

Vivax malaria in pregnancy and lactation: a long way to health equity.

BACKGROUND: The Sustainable Development Goals (SDG) call for increased gender equity and reduction in malaria-related mortality and morbidity. Plasmodium vivax infections in pregnancy are associated with maternal anaemia and increased adverse perinatal outcomes. Providing radical cure for women with 8-aminoquinolines (e.g., primaquine) is hindered by gender-specific complexities. CASE PRESENTATION: A symptomatic episode of vivax malaria at 18 weeks of gestation in a primigravid woman was associated with maternal anaemia, a recurrent asymptomatic P. vivax episode, severe intra-uterine growth restriction with no other identifiable cause and induction to reduce the risk of stillbirth. At 5 months postpartum a qualitative glucose-6-phosphate dehydrogenase (G6PD) point-of-care test was normal and radical cure with primaquine was prescribed to the mother. A 33% fractional decrease in haematocrit on day 7 of primaquine led to further testing which showed intermediate phenotypic G6PD activity; the G6PD genotype could not be identified. Her infant daughter was well throughout maternal treatment and found to be heterozygous for Mahidol variant. CONCLUSION: Adverse effects of vivax malaria in pregnancy, ineligibility of radical cure for pregnant and postpartum women, and difficulties in diagnosing intermediate levels of G6PD activity multiplied morbidity in this woman. Steps towards meeting the SDG include prevention of malaria in pregnancy, reducing unnecessary exclusion of women from radical cure, and accessible quantitative G6PD screening in P. vivax-endemic settings.

The impact of using primaquine without prior G6PD testing: a case series describing the obstacles to the medical management of haemolysis.

Radical cure of Plasmodium vivax malaria in glucose-6-phosphate dehydrogenase (G6PD) deficient individuals employs weekly primaquine dosing. This is the only recommended regimen for this patient sub-group. If national malaria programs mandate daily primaquine dosing (the recommended regimen for G6PD normal individuals), then G6PD testing before prescription is necessary to avoid iatrogenic haemolysis in G6PD deficient individuals. In this case series, two P. vivax infected patients with unknown G6PD status from two different countries were prescribed primaquine as per national malaria program guidelines. During treatment both patients presented to the clinic with symptoms of anaemia after taking primaquine incorrectly. The clinical management of the iatrogenic severe haemolysis that occurred in these patients demonstrates the various adverse effects primaquine can cause, that other common medical treatments also have haemolytic potential, and how the diagnosis of G6PD deficiency can be elusive during acute haemolysis. Health care providers should provide careful instructions about primaquine dosing, be watchful for haemolysis, and have a high index of suspicion for G6PD deficiency in the presence of haemolysis if the G6PD status is previously unknown.

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.

Validation of the quantitative point-of-care CareStart biosensor for assessment of G6PD activity in venous blood.

INTRODUCTION: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy in the human population affecting an estimated 8% of the world population, especially those living in areas of past and present malaria endemicity. Decreased G6PD enzymatic activity is associated with drug-induced hemolysis and increased risk of severe neonatal hyperbilirubinemia leading to brain damage. The G6PD gene is on the X chromosome therefore mutations cause enzymatic deficiency in hemizygote males and homozygote females while the majority of heterozygous females have an intermediate activity (between 30-80% of normal) with a large distribution into the range of deficiency and normality. Current G6PD qualitative tests are unable to diagnose G6PD intermediate activities which could hinder wide use of 8-aminoquinolines for Plasmodium vivax elimination. The aim of the study was to assess the diagnostic performances of the new Carestart G6PD quantitative biosensor. METHODS: A total of 150 samples of venous blood with G6PD deficient, intermediate and normal phenotypes were collected among healthy volunteers living along the north-western Thailand-Myanmar border. Samples were analyzed by complete blood count, by gold standard spectrophotometric assay using Trinity kits and by the latest model of Carestart G6PD biosensor which analyzes both G6PD and hemoglobin. RESULTS: Bland-Altman comparison of the CareStart normalized G6PD values to that of the gold standard assay showed a strong bias in values resulting in poor area under-the-curve values for both 30% and 80% thresholds. Performing a receiver operator curve identified threshold values for the CareStart product equivalent to the 30% and 80% gold standard values with good sensitivity and specificity values, 100% and 92% (for 30% G6PD activity) and 92% and 94% (for 80% activity) respectively. CONCLUSION: The Carestart G6PD biosensor represents a significant improvement for quantitative diagnosis of G6PD deficiency over previous versions. Further improvements and validation studies are required to assess its utility for informing radical cure decisions in malaria endemic settings.

Diagnostic performances of the fluorescent spot test for G6PD deficiency in newborns along the Thailand-Myanmar border: A cohort study.

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an inherited enzymatic disorder associated with severe neonatal hyperbilirubinemia and acute haemolysis after exposure to certain drugs or infections. The disorder can be diagnosed phenotypically with a fluorescent spot test (FST), which is a simple test that requires training and basic laboratory equipment. This study aimed to assess the diagnostic performances of the FST used on umbilical cord blood by locally-trained staff and to compare test results of the neonates at birth with the results after one month of age. Methods: We conducted a cohort study on newborns at the Shoklo Malaria Research Unit, along the Thai-Myanmar border between January 2015 and May 2016. The FST was performed at birth on the umbilical cord blood by locally-trained staff and quality controlled by specialised technicians at the central laboratory. The FST was repeated after one month of age. Genotyping for common local G6PD mutations was carried out for all discrepant results. Results: FST was performed on 1521 umbilical cord blood samples. Quality control and genotyping revealed 10 misdiagnoses. After quality control, 10.7% of the males (84/786) and 1.2% of the females (9/735) were phenotypically G6PD deficient at birth. The FST repeated at one month of age or later diagnosed 8 additional G6PD deficient infants who were phenotypically normal at birth. Conclusions: This study shows the short-comings of the G6PD FST in neonatal routine screening and highlights the importance of training and quality control. A more conservative interpretation of the FST in male newborns could increase the diagnostic performances. Quantitative point-of-care tests might show higher sensitivity and specificity for diagnosis of G6PD deficiency on umbilical cord blood and should be investigated.

Prevalences of inherited red blood cell disorders in pregnant women of different ethnicities living along the Thailand-Myanmar border.

Background: Inherited red blood cell disorders are prevalent in populations living in malaria endemic areas; G6PD deficiency is associated with oxidant-induced haemolysis and abnormal haemoglobin variants may cause chronic anaemia. In pregnant women, microcytic anaemia caused by haemoglobinopathies mimics iron deficiency, complicating diagnosis and treatment. Anaemia during pregnancy is associated with morbidity and mortality. The aim of this study was to characterise the prevalence of G6PD deficiency and haemoglobinopathies  among the pregnant population living along the Thailand-Myanmar border. Pregnant women attending antenatal clinics in this area belong to several distinct ethnic groups. Methods: Data were available for 13,520 women attending antenatal care between July 2012 and September 2016. Screening for G6PD deficiency was done by fluorescent spot test routinely. G6PD genotyping and quantitative phenotyping by spectrophotometry were analysed in a subsample of women. Haemoglobin variants were diagnosed by HPLC or capillary electrophoresis and molecular methods. The prevalence and distribution of inherited red blood cell disorders was analysed with respect to ethnicity. Results: G6PD deficiency was common, especially in the Sgaw Karen ethnic group, in whom the G6PD Mahidol variant allele frequency was 20.7%. Quantitative G6PD phenotyping showed that 60.5% of heterozygous women had an intermediate enzymatic activity between 30% and 70% of the population median. HbE, beta-thalassaemia trait and Hb Constant Spring were found overall in 15.6% of women. Only 45.2% of women with low percentage of HbA 2 were carriers of mutations on the alpha globin genes. Conclusions: Distribution of G6PD and haemoglobin variants varied among the different ethnic groups, but the prevalence was generally high throughout the cohort. These findings encourage the implementation of an extended program of information and genetic counselling to women of reproductive age and will help inform future studies and current clinical management of anaemia in the pregnant population in this region.

Single Low Dose Primaquine (0.25 mg/kg) Does Not Cause Clinically Significant Haemolysis in G6PD Deficient Subjects.

BACKGROUND: Primaquine is the only drug consistently effective against mature gametocytes of Plasmodium falciparum. The transmission blocking dose of primaquine previously recommended was 0.75 mg/kg (adult dose 45 mg) but its deployment was limited because of concerns over haemolytic effects in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. G6PD deficiency is an inherited X-linked enzymatic defect that affects an estimated 400 million people around the world with high frequencies (15-20%) in populations living in malarious areas. To reduce transmission in low transmission settings and facilitate elimination of P. falciparum, the World Health Organization now recommends adding a single dose of 0.25 mg/kg (adult dose 15 mg) to Artemisinin-based Combination Therapies (ACTs) without G6PD testing. Direct evidence of the safety of this low dose is lacking. Adverse events and haemoglobin variations after this treatment were assessed in both G6PD normal and deficient subjects in the context of targeted malaria elimination in a malaria endemic area on the North-Western Myanmar-Thailand border where prevalence of G6PD deficiency (Mahidol variant) approximates 15%. METHODS AND FINDINGS: The tolerability and safety of primaquine (single dose 0.25 mg base/kg) combined with dihydroartemisinin-piperaquine (DHA-PPQ) given three times at monthly intervals was assessed in 819 subjects. Haemoglobin concentrations were estimated over the six months preceding the ACT + primaquine rounds of mass drug administration. G6PD deficiency was assessed with a phenotypic test and genotyping was performed in male subjects with deficient phenotypes and in all females. Fractional haemoglobin changes in relation to G6PD phenotype and genotype and primaquine round were assessed using linear mixed-effects models. No adverse events related to primaquine were reported during the trial. Mean fractional haemoglobin changes after each primaquine treatment in G6PD deficient subjects (-5.0%, -4.2% and -4.7%) were greater than in G6PD normal subjects (0.3%, -0.8 and -1.7%) but were clinically insignificant. Fractional drops in haemoglobin concentration larger than 25% following single dose primaquine were observed in 1.8% of the population but were asymptomatic. CONCLUSIONS: The single low dose (0.25mg/kg) of primaquine is clinically well tolerated and can be used safely without prior G6PD testing in populations with high prevalence of G6PD deficiency. The present evidence supports a broader use of low dose primaquine without G6PD testing for the treatment and elimination of falciparum malaria. TRIAL REGISTRATION: ClinicalTrials.gov NCT01872702.