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.

Antigen concentration, viral load, and test performance for SARS-CoV-2 in multiple specimen types

The relationship between N-antigen concentration and viral load within and across different specimens guides the clinical performance of rapid diagnostic tests (RDT) in different uses. A prospective study was conducted in Porto Velho, Brazil, to investigate RDT performance in different specimen types as a function of the correlation between antigen concentration and viral load. The study included 214 close contacts with recent exposures to confirmed cases, aged 12 years and older and with various levels of vaccination. Antigen concentration was measured in nasopharyngeal swab (NPS), anterior nares swab (ANS), and saliva specimens. Reverse transcriptase (RT)-PCR was conducted on the NPS and saliva specimens, and two RDTs were conducted on ANS and one RDT on saliva. Antigen concentration correlated well with viral load when measured in the same specimen type but not across specimen types. Antigen levels were higher in symptomatic cases compared to asymptomatic/oligosymptomatic cases and lower in saliva compared to NPS and ANS samples. Discordant results between the RDTs conducted on ANS and the RT-PCR on NPS were resolved by antigen concentration values. The analytical limit-of-detection of RDTs can be used to predict the performance of the tests in populations for which the antigen concentration is known. The antigen dynamics across different sample types observed in SARS-CoV-2 disease progression support use of RDTs with nasal samples. Given lower antigen concentrations in saliva, rapid testing using saliva is expected to require improved RDT analytical sensitivity to achieve clinical sensitivity similar to rapid testing of nasal samples.

Screening for Severe Acute Respiratory Syndrome Coronavirus 2 in Close Contacts of Individuals With Confirmed Infection: Performance and Operational Considerations

BACKGROUND

Point-of-care and decentralized testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical to inform public health responses. Performance evaluations in priority use cases such as contact tracing can highlight trade-offs in test selection and testing strategies.

METHODS

A prospective diagnostic accuracy study was conducted among close contacts of coronavirus disease 2019 (COVID-19) cases in Brazil. Two anterior nares swabs (ANS), a nasopharyngeal swab (NPS), and saliva were collected at all visits. Vaccination history and symptoms were assessed. Household contacts were followed longitudinally. Three rapid antigen tests and 1 molecular method were evaluated for usability and performance against reference reverse-transcription polymerase chain reaction (RT-PCR) on nasopharyngeal swab specimens.

RESULTS

Fifty index cases and 214 contacts (64 household) were enrolled. Sixty-five contacts were RT-PCR positive during ≥1 visit. Vaccination did not influence viral load. Gamma variants were most prevalent; Delta variants emerged increasingly during implementation. The overall sensitivity of evaluated tests ranged from 33% to 76%. Performance was higher among symptomatic cases and those with cycle threshold (Ct) values <34 and lower among oligosymptomatic or asymptomatic cases. Assuming a 24-hour time to results for RT-PCR, the cumulative sensitivity of an anterior nares swab rapid antigen test was >70% and almost 90% after 4 days.

CONCLUSIONS

The near-immediate time to results for antigen tests significantly offsets lower analytical sensitivity in settings where RT-PCR results are delayed or unavailable.

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.

Evaluation of a point-of-care diagnostic to identify glucose-6-phosphate dehydrogenase deficiency in Brazil

Background

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common enzyme deficiency, prevalent in many malaria-endemic countries. G6PD-deficient individuals are susceptible to hemolysis during oxidative stress, which can occur from exposure to certain medications, including 8-aminoquinolines used to treat Plasmodium vivax malaria. Accordingly, access to point-of-care (POC) G6PD testing in Brazil is critical for safe treatment of P. vivax malaria.

Methodology/Principal findings

This study evaluated the performance of the semi-quantitative, POC STANDARD G6PD Test (SD Biosensor, Republic of Korea). Participants were recruited at clinics and through an enriched sample in Manaus and Porto Velho, Brazil. G6PD and hemoglobin measurements were obtained from capillary samples at the POC using the STANDARD and HemoCue 201+ (HemoCue AB, Sweden) tests. A thick blood slide was prepared for malaria microscopy. At the laboratories, the STANDARD and HemoCue tests were repeated on venous samples and a quantitative spectrophotometric G6PD reference assay was performed (Pointe Scientific, Canton, MI). G6PD was also assessed by fluorescent spot test. In Manaus, a complete blood count was performed.

Samples were analyzed from 1,736 participants. In comparison to spectrophotometry, the STANDARD G6PD Test performed equivalently in determining G6PD status in venous and capillary specimens under varied operating temperatures. Using the manufacturer-recommended reference value thresholds, the test’s sensitivity at the <30% threshold on both specimen types was 100% (95% confidence interval [CI] venous 93.6%–100.0%; capillary 93.8%–100.0%). Specificity was 98.6% on venous specimens (95% CI 97.9%–99.1%) and 97.8% on capillary (95% CI 97.0%–98.5%). At the 70% threshold, the test’s sensitivity was 96.9% on venous specimens (95% CI 83.8%–99.9%) and 94.3% on capillary (95% CI 80.8%–99.3%). Specificity was 96.5% (95% CI 95.0%–97.6%) and 92.3% (95% CI 90.3%–94.0%) on venous and capillary specimens, respectively.

Conclusion/Significance

The STANDARD G6PD Test is a promising tool to aid in POC detection of G6PD deficiency in Brazil.

Trial registration

This study was registered with ClinicalTrials.gov (identifier: NCT04033640).

G6PD deficiency affects an estimated 500 million people worldwide and is prevalent in many malaria-endemic settings. People with G6PD deficiency are at risk of hemolysis when exposed to certain medications, including 8-aminoquinoline drugs used to treat Plasmodium vivax malaria. Increased access to testing for G6PD deficiency at or near the point of care is critical for expanding the safe treatment of P. vivax malaria. In this study, we aimed to evaluate the performance of a point-of-care, semi-quantitative test for G6PD deficiency, the STANDARD G6PD Test, in a malaria-endemic setting in Brazil. The test was evaluated on both capillary and venous blood samples across a broad range of operating temperatures. The findings show that the STANDARD G6PD Test performed equivalently to the reference test in its ability to diagnose G6PD deficiency at the point of care. The STANDARD G6PD Test is a promising tool to aid in detecting G6PD deficiency at the point of care in Brazil.

Persistence of oral pre-exposure prophylaxis (PrEP) among adolescent girls and young women initiating PrEP for HIV prevention in Kenya

The Determined, Resilient, Empowered, AIDS-free, Mentored, and Safe (DREAMS) Initiative aims to reduce HIV infections among adolescent girls and young women (AGYW) in Africa. Oral pre-exposure prophylaxis (PrEP) is offered through DREAMS in Kenya to eligible AGYW in high burden counties including Kisumu and Homa Bay. This study examines PrEP persistence among AGYW in high burden community-based PrEP delivery settings. We evaluated PrEP persistence among AGYW in the DREAMS PrEP program in Kisumu and Homa Bay using survival analysis and programmatic PrEP refill data collected between March through December 2017. Among 1,259 AGYW who initiated PrEP during the study period, the median persistence time in the program was 56 days (95% CI: 49-58 days) and the proportion who persisted 3 months later was 37% (95% CI: 34-40%). Persistence varied by county (p < 0.001), age at PrEP initiation (p = 0.002), marital status (p = 0.008), transactional sex (p = 0.002), gender-based violence (GBV) experience (p = 0.009) and current school attendance (p = 0.001) at DREAMS enrollment. Persistence did not vary with orphan status, food insecurity, condom use, age at first sexual encounter or engagement in age-disparate sex at DREAMS enrollment. Targeted strategies are needed to improve AGYW retention in the PrEP program.

Evaluating the nutritional content of an insect-fortified food for the child complementary diet in Ghana

BACKGROUND

Due to rising food insecurity, natural resource scarcity, population growth, and the cost of and demand for animal proteins, insects as food have emerged as a relevant topic. This study examines the nutrient content of the palm weevil larva (Rhynchophorus phoenicis), a traditionally consumed edible insect called akokono in Ghana, and assesses its potential as an animal-source, complementary food.

METHODS

Akokono in two "unmixed" forms (raw, roasted) and one "mixed" form (akokono-groundnut paste) were evaluated for their macronutrient, micronutrient, amino acid, and fatty acid profiles.

RESULTS

Nutrient analyses revealed that a 32 g (2 tbsp.) serving of akokono-groundnut paste, compared to recommended daily allowances or adequate intakes (infant 7-12 months; child 1-3 years), is a rich source of protein (99%; 84%), minerals [copper (102%; 66%), magnesium (54%; 51%), zinc (37%; 37%)], B-vitamins [niacin (63%; 42%), riboflavin (26%; 20%), folate (40%; 21%)], Vitamin E (a-tocopherol) (440%; 366%), and linoleic acid (165%; 108%). Feed experiments indicated that substituting palm pith, the typical larval diet, for pito mash, a local beer production by-product, increased the carbohydrate, potassium, calcium, sodium, and zinc content of raw akokono. Akokono-groundnut paste meets (within 10%) or exceeds the levels of essential amino acids specified by the Institute of Medicine criteria for animal-source foods, except for lysine.

CONCLUSIONS

Pairing akokono with other local foods (e.g., potatoes, soybeans) can enhance its lysine content and create a more complete dietary amino acid profile. The promotion of akokono as a complementary food could play an important role in nutrition interventions targeting children in Ghana.

Potential new tool for anemia screening: An evaluation of the performance and usability of the TrueHb Hemometer

In low- and middle-income countries, many women experience anemia during pregnancy due to insufficient dietary intake of key micronutrients, parasitic infections, hemoglobinopathies, and chronic infections. Maternal anemia increases perinatal risks for both mothers and infants, and slow progress to reduce the prevalence may be due in part to the lack of affordable tools to quantify hemoglobin levels in antenatal care (ANC) clinics. A simple, inexpensive, accurate, and robust diagnostic is needed to measure hemoglobin in ANC. This study evaluated the performance and usability of the TrueHb Hemometer. A cross-sectional diagnostic accuracy study was conducted to compare the accuracy of the TrueHb and the HemoCue® 201+ using capillary samples. Next, analytical performance (precision, coefficient of variation, R²) of the TrueHb was evaluated in varying environmental conditions using linearity panels with serial dilutions of venous blood samples. Lastly, the usability of the TrueHb Hemometer was assessed across three domains (effectiveness, efficiency, and satisfaction) by 20 ANC providers in Ghana. Capillary blood test results were not well correlated (R² = 0.35) between the TrueHB and HemoCue201+, but 80% of TrueHb measurements were within +/-1.0 g/dl of the HemoCue® 201+ hemoglobin values. Precision tests indicated similar mean values across the three environmental conditions (CV<6%). At 21°C, the TrueHb follows a linear relationship (R²≥0.96) but does not generate accurate readings below 4.0 g/dl. At 30°C and 37°C, the TrueHb follows a linear relationship (R² > 0.90) but begins to underestimate the hemoglobin concentration below 7.0 g/dl. The usability study identified potential failure modes due to inadequate instructions and device feedback. With some modifications, both to the product and to the instructions for use, the TrueHb may be suitable for use in ANC settings to help fill the diagnostic gap for anemia screening during pregnancy. Further testing is required with anemic populations in LMIC settings.

Bacterial community dynamics in lait caillé, a traditional product of spontaneous fermentation from Senegal

Spontaneously fermented food products contain a complex, natural microbial community with potential probiotic activity. The addition of a health-promoting, probiotic bacterium to these products ensures the delivery of that probiotic activity to consumers. Here, we assess the microbial community of a traditional Senegalese milk product produced by spontaneous fermentation, called lait caillé. We produced the lait caillé in a traditional way and added a probiotic starter containing Lactobacillus rhamnosus yoba 2012 to the traditional process. We found various species that are known for their ability to ferment milk, including species from the genera Lactobacillus, Acetobacter, Lactococcus, and Streptococcus. Our results show that the addition of L. rhamnosus to the inoculum, can result in detectable levels of this strain in the final product, ranging between 0.2 and 1 percent of the total bacterial population. Subsequent rounds of fermentation using passive back-slopping without the addition of new L. rhamnosus led to a loss of this strain from the community of fermenting bacteria. Our results suggest that the addition of probiotic strains at every fermentation cycle can enrich the existing complex communities of traditionally fermented lait caillé while traditional bacterial strains remain dominant in the bacterial communities.

Naturally Fermented Milk From Northern Senegal: Bacterial Community Composition and Probiotic Enrichment With Lactobacillus rhamnosus

A variety of foods fermented with lactic acid bacteria serve as dietary staples in many African communities; yet, their bacterial profiles are poorly characterized. The integration of health-promoting probiotics into naturally fermented milk products could make a profound impact on human health. Here, we characterize the bacterial community composition of a naturally fermented milk product (lait caillé) from northern Senegal, prepared in wooden bowls (lahals) with a bacterial biofilm to steer the fermentation process. We incorporated a probiotic starter culture containing the most documented probiotic strain Lactobacillus rhamnosus GG (generic strain name yoba 2012) into the local fermentation process. Bar-coded 16S rRNA amplicon sequencing of lait caillé samples indicated that the bacterial community of lait caillé has high species richness with over 100 bacterial genera; however, few have high abundance. In contrast to the diverse bacterial compositions of other characterized naturally fermented milk products, the composition of lait caillé predominantly consists of the lactic acid bacteria Streptococcus and Lactobacillus, resembling the bacterial composition in regular yogurt. The bacterial community composition of lait caillé varies geographically based on the presence of some genera, including Lactoccoccus, Enterococcus, Bifidobacterium, and Bacillus, but this trend is not consistent within production communities. The diversity of bacterial communities is much higher in the lahal biofilm than in the naturally fermented milk products, which is in turn greater than in commercial yogurts. Addition of a starter culture with L. rhamnosus yoba 2012 to milk in lahals led to substantial growth of this probiotic bacterium during the fermentation process. Two independent quantitative PCR-analyses specific for L. rhamnosus yoba 2012 indicated a 20- to 60-fold increase in the total number of probiotic bacteria in the first batch after inoculation. A similar increase of the probiotic was observed in a variation of lait caillé prepared with carbohydrate-rich millet granules (thiakry) added prior to fermentation. This study shows the feasibility of integrating health-promoting probiotic strains into naturally fermented foods produced in regions with a high prevalence of malnutrition.

Using cognitive mapping to understand Senegalese infant and young child feeding decisions

Caregivers make decisions about how to feed their infants and young children based on complex interactions of knowledge, beliefs, and values, as well as assessments of situational determinants, including economic and social constraints and opportunities. Because of the relationship of these factors to the adoption of new feeding behaviours, the development of nutrition interventions for this age group must be grounded in knowledge about the target population. This paper presents the results of a study that used cognitive mapping techniques to gain insight into mothers' knowledge and perceptions of foods for infants and young children and examine their significance for feeding decisions in Saint-Louis, northern Senegal. Guided by mixed-methods protocols from the Focused Ethnographic Study for Infant and Young Child Feeding Manual, in-depth interviews that included qualitative discussions and cognitive mapping techniques were conducted with 46 mothers in rural and peri-urban communities. We explored mothers' perceptions about five dimensions that affect food decision-making-healthiness, convenience, child acceptance, appeal, and modernity-and the relationship of these dimensions to 38 local food items. Data analysis entailed a combination of qualitative thematic analysis and descriptive statistics. In both communities, "healthiness" was the most valued dimension for food decision-making by a large margin, followed by child acceptance, appeal, modernity, and convenience. We explore how different interpretations and definitions of these dimensions, and their relationship to specific local food items, may influence the design and planning of nutrition interventions. The results support the importance of mixed-methods formative research to illuminate the emic perspectives of caregivers.

Results of Applying Cultural Domain Analysis Techniques and Implications for the Design of Complementary Feeding Interventions in Northern Senegal

Background:

Designing effective nutrition interventions for infants and young children requires knowledge about the population to which the intervention is directed, including insights into the cognitive systems and values that inform caregiver feeding practices.

Objective:

To apply cultural domain analysis techniques in the context of implementation research for the purpose of understanding caregivers’ knowledge frameworks in Northern Senegal with respect to infant and young child (IYC) feeding. This study was intended to inform decisions for interventions to improve infant and young child nutrition.

Methods:

Modules from the Focused Ethnographic Study for Infant and Young Child Feeding Manual were employed in interviews with a sample of 126 key informants and caregivers from rural and peri-urban sites in the Saint-Louis region of northern Senegal. Descriptive statistics, cluster analysis, and qualitative thematic analysis were used to analyze the data.

Results:

Cluster analysis showed that caregivers identified 6 food clusters: heavy foods, light foods, snack foods, foraged foods, packaged foods, and foods that are good for the body. The study also revealed similarities and differences between the 2 study sites in caregivers’ knowledge frameworks.

Conclusions:

The demonstration of differences between biomedical concepts of nutrition and the knowledge frameworks of northern Senegalese women with regard to IYC feeding highlights the value of knowledge about emic perspectives of local communities to help guide decisions about interventions to improve nutrition.

An Exploration of Edible Palm Weevil Larvae (Akokono) as a Source of Nutrition and Livelihood: Perspectives From Ghanaian Stakeholders

BACKGROUND

Meeting the nutritive needs of infants and young children is a challenge in Ghana. Alternative animal source foods, including insects, could enhance infant and young child dietary quality while also improving livelihoods.

OBJECTIVE

To investigate the perspectives of Ghanaian stakeholders on the acceptability of the palm weevil larvae ( akokono) as a food source and the feasibility of micro-farming this local edible insect as a complementary food for infants and young children.

METHODS

We conducted an ethnographic study in the Brong-Ahafo Region of Ghana. First, 48 caregivers were asked questions about feeding and care practices, including attitudes toward production and consumption of akokono. Then, a selection of previously interviewed respondents joined 1 of 8 focus group discussions to provide further insight on key themes that emerged from earlier interviews. Concurrently, interviews with 25 other key local stakeholders were conducted.

RESULTS

Respondents generally had favorable perceptions of akokono as a nutritious food. A small minority would not consume akokono for religious reasons. Key factors positively influencing the acceptability of akokono as a complementary food were familiarity with the consumption of akokono by the primary caregiver and health worker endorsement of akokono. Stakeholders consider the larvae farmable and were open to its domestication.

CONCLUSIONS

Anticipated barriers to scaling up akokono micro-farming include a need for greater familiarity with and acceptance of the insect as food for infants and young children and creation of a sustainable market. Engagement with stakeholders, including health workers, will facilitate use of akokono as a complementary food.

Patterns of cultural consensus and intracultural diversity in Ghanaian complementary feeding practices

Designing effective interventions to improve infant and young child (IYC) feeding requires knowledge about determinants of current practices, including cultural factors. Current approaches to obtaining and using research on culture tend to assume cultural homogeneity within a population. The purpose of this study was to examine the extent of cultural consensus (homogeneity) in communities where interventions to improve IYC feeding practices are needed to address undernutrition during the period of complementary feeding. A second, related objective was to identify the nature of intracultural variation, if such variation was evident. Selected protocols from the Focused Ethnographic Study for Infant and Young Child Feeding Manual were administered to samples of key informants and caregivers in a peri-urban and a rural area in Brong-Ahafo, Ghana. Cultural domain analysis techniques (free listing, caregiver assessment of culturally significant dimensions, and food ratings on these dimensions), as well as open-ended questions with exploratory probing, were used to obtain data on beliefs and related practices. Results reveal generally high cultural consensus on the 5 dimensions that were assessed (healthiness, appeal, child acceptance, convenience, and modernity) for caregiver decisions and on their ratings of individual foods. However, thematic analysis of caregiver narratives indicates that the meanings and content of the constructs connoted by the dimensions differed widely among individual mothers. These findings suggest that research on cultural factors that affect IYC practices, particularly cultural beliefs, should consider the nature and extent of cultural consensus and intracultural diversity, rather than assuming cultural homogeneity.

[Health for all--the last progress assessment before the year 2000]

In the framework of the tri-annual report to WHO of progress towards "Health for all" the specific question concerning reduction of inequity in health is addressed. Regional variations in health status represent an important aspect of that question which is of particular interest in a federal country where major public health competencies are located at the regional level (cantons in Switzerland). Health status is described by both mortality measures (main causes of death) in the population aged 0-64 years and morbidity indicators (rates of disability pensioners) in the same age group. In addition to the comparison of mortality and morbidity rates between cantons an "index of dissimilarity" (DI) was used. For both criteria, changes over a time period of 10 to 12 years were considered. Results show decreasing trends of mortality from all and main causes of death in both sexes. While this tendency goes along with decreasing dissimilarity as to male overall mortality, the corresponding female DI increases, indicating an increase in inequity between the cantons. A similar pattern is observed as to morbidity: although rates of disability pensioners went up for both sexes, this increase resulted in a lower DI-value for men but a higher one for women. The results are discussed against the background of socioeconomic differences (e.g. unemployment) between the cantons studied.