The Primaquine Problem-and the Solution? Point-of-care Diagnostics for Glucose 6-Phosphate Dehydrogenase Deficiency

Performance of a Commercial Multiplex Allele-Specific Polymerase Chain Reaction Kit to Genotype African-Type Glucose-6-Phosphate Dehydrogenase Deficiency

8-Aminoquinoline antimalarial drugs (primaquine, tafenoquine) are required for complete cure of Plasmodium vivax malaria, but they are contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. In the absence of spectrophotometry, which is a gold standard for measuring G6PD activity, G6PD genotyping is one of the alternatives to establish a database and distribution map of G6PD enzyme deficiency in Mauritania, which has become a new epicenter of P. vivax malaria in West Africa. The aim of our study was to assess the performance of multiplex allele-specific polymerase chain reaction (PCR) (African-type Diaplex C™ G6PD kit) against PCR-restriction fragment length polymorphism and sequencing. Of 146 mutations associated with G6PD A- genotypes in 177 blood samples from Mauritanian patients, all but two samples were identified correctly using multiplex allele-specific PCR (100% sensitivity and 99% specificity; "almost perfect agreement" between allele-specific PCR and PCR-restriction fragment length polymorphism/sequencing, with a kappa coefficient of 0.977). Despite a suboptimal PCR protocol for dried blood spots and the inability of the commercial assay to predict unequivocally the G6PD enzyme level in heterozygous females, the African-type Diaplex C™ G6PD genotyping kit seemed to be a valuable screening tool for male subjects and for research purposes in resource-limited countries where spectrophotometer and DNA sequencing are not available.

An Evaluation of a New Quantitative Point-of Care Diagnostic to Measure Glucose-6-phosphate Dehydrogenase Activity

Malaria continues to be one of the most crucial infectious burdens in endemic areas worldwide, as well as for travelers visiting malaria transmission regions. It has been reported that 8-aminoquinolines are effective against the Plasmodium species, particularly primaquine, for anti-hypnozoite therapy in P. vivax malaria. However, primaquine causes acute hemolytic anemia in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Therefore, G6PD deficiency testing should precede hypnozoite elimination with 8-aminoquinoline. Several point-of-care devices have been developed to detect G6PD deficiency. The aim of the present study was to evaluate the performance of a novel, quantitative G6PD diagnostics based on a metagenomic blue fluorescent protein (mBFP). We comparatively evaluated the sensitivity and specificity of the G6PD diagnostic modality with standard methods using 120 human whole blood samples. The G6PD deficiency was spectrophotometrically confirmed. The performance of the G6PD quantitative test kit was compared with that of a licensed control medical device, the G6PD strip. The G6PD quantitative test kit had a sensitivity of 95% (95% confidence interval (CI): 89.3–100%) and a specificity of 100% (95% CI: 94.3–100%). This study shows that the novel diagnostic G6PD quantitative test kit could be a cost-effective and time-efficient, and universally mandated screening tool for G6PD deficiency.

Assessment of CareStart G6PD rapid diagnostic test and CareStart G6PD biosensor in Mauritania

BACKGROUND

The elimination of Plasmodium vivax malaria requires 8-aminoquinolines, which are contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to the risk of acute haemolytic anaemia. Several point-of-care devices have been developed to detect G6PD deficiency. The objective of the present study was to evaluate the performance of two of these devices against G6PD genotypes in Mauritania.

METHODS

Outpatients were screened for G6PD deficiency using CareStart™ rapid diagnostic test (RDT) and CareStart™ G6PD biosensor in Nouakchott, Mauritania, in 2019-2020. African-type and Mediterranean-type G6PD genotypes commonly observed in Africa were determined by polymerase chain reaction-restriction fragment length polymorphism and sequencing. Qualitative variables were compared using Fisher's exact test.

RESULTS

Of 323 patients (74 males and 249 females), 5 males and 2 homozygous females had the African-type A- genotype: A-(202) in 3 males and 2 females and G6PD A-(968) in 2 males. Among heterozygous females, 13 carried G6PD A-(202), 12 G6PD A-(968), and 3 G6PD A-(542) variants. None had the Mediterranean-type G6PD genotype. Eight had a positive G6PD RDT result, including all 7 hemizygous males and homozygous females with A- or A-A- (0.12 to 2.34 IU/g haemoglobin, according to G6PD biosensor), but RDT performed poorly (sensitivity, 11.1% at the cut-off level of < 30%) and yielded many false negative tests. Thirty-seven (50.0%) males and 141 (56.6%) females were anaemic. The adjusted median values of G6PD activity were 5.72 and 5.34 IU/g haemoglobin in non-anaemic males (n = 35) and non-anaemic males and females (n = 130) with normal G6PD genotypes using G6PD biosensor, respectively. Based on the adjusted median of 5.34 IU/g haemoglobin, the performance of G6PD biosensor against genotyping was as follows: at 30% cut-off, the sensitivity and specificity were 85.7% and 91.7%, respectively, and at 80% cut-off, the sensitivity was 100% while the specificity was 64.9%.

CONCLUSIONS

Although this pilot study supports the utility of biosensor to screen for G6PD deficiency in patients, further investigation in parallel with spectrophotometry is required to promote and validate a more extensive use of this point-of-care device in areas where P. vivax is highly prevalent in Mauritania.

Evolving Role of Pharmacogenetic Biomarkers to Predict Drug-Induced Hematological Disorders

ABSTRACT

Drug-induced hematological disorders constitute up to 30% of all blood dyscrasias seen in the clinic. Hematologic toxicity from drugs may range from life-threatening marrow aplasia, agranulocytosis, hemolysis, thrombosis to mild leukopenia, and thrombocytopenia. Pathophysiologic mechanisms underlying these disorders vary from an extension of the pharmacological effect of the drug to idiosyncratic and immune-mediated reactions. Predicting these reactions is often difficult, and this makes clinical decision-making challenging. Evidence supporting the role of pharmacogenomics in the management of these disorders in clinical practice is rapidly evolving. Despite the Clinical Pharmacology Implementation Consortium and Pharmacogenomics Knowledge Base recommendations, few tests have been incorporated into routine practice. This review aims to provide a comprehensive summary of the various drugs which are implicated for the hematological adverse events, their underlying mechanisms, and the current evidence and practical recommendations to incorporate pharmacogenomic testing in clinical care for predicting these disorders.