Abstract
BackgroundGlucose-6-phosphate dehydrogenase (G6PD) deficiency is a common human enzyme deficiency. It is characterized by abnormally low levels of G6PD activity. Individuals with G6PD deficiency are at risk of undergoing acute haemolysis when exposed to 8‒aminoquinoline-based drugs, such as primaquine. For this reason it is imperative to identify individuals with G6PD deficiency prior to administering these anti-malarial drugs. There is a need for the development and evaluation of point-of-care G6PD deficiency screening tests suitable for areas of the developing world where malarial treatments are frequently administered. The development and evaluation of new G6PD tests will be greatly assisted with the availability of specimen repositories.MethodsCryopreservation of erythrocytes was evaluated as a means to preserve G6PD activity. Blood specimens from 31 patients including ten specimens with normal G6PD activity, three with intermediate activity, and 18 with deficient activity were cryopreserved for up to six months.ResultsGood correlation in G6PD activity between fresh and cryopreserved specimens (R2 = 0.95). The cryopreserved specimens show an overall small drop in mean G6PD activity of 0.23 U/g Hb (P=0.23). Cytochemical staining showed that intracellular G6PD activity distribution within the red blood cell populations is preserved during cryopreservation. Furthermore, the mosaic composition of red blood cells in heterozygous women is also preserved for six months or more. The fluorescent spot and the BinaxNOW qualitative tests for G6PD deficiency also showed high concordance in G6PD status determination between cryopreserved specimens and fresh specimens.ConclusionsA methodology for establishing a specimen panel for evaluation of G6PD tests is described. The approach is similar to that used in several malaria research facilities for the cryopreservation of parasites in clinical specimens and axenic cultures. Specimens stored in this manner will aid both the development and evaluation of current and emerging G6PD tests. The availability of G6PD tests is a critical bottleneck to broader access to drugs that confer radical cure of Plasmodium vivax, a requirement for elimination of malaria.
Highlights
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common human enzyme deficiency
The mean and the standard deviation (SD) of the quantitative Trinity G6PD assay were determined for all specimens at Day 0, and all specimens were thawed between Day 0 and Day 200; summary statistics were calculated for specimens stratified by the following cryopreservation time intervals: i) specimens thawed between Day 0 and Day after cryopreservation, ii) specimens thawed between Day and Day after cryopreservation, and iii) specimens thawed between Day and Day 200 after cryopreservation
All specimens were characterized for G6PD activity with the Trinity quantitative assay as well as by flow cytometry assay as described in Methods, both prior to cryopreservation (Day 0 data) and just after thawing
Summary
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common human enzyme deficiency It is characterized by abnormally low levels of G6PD activity. Individuals with G6PD deficiency are at risk of undergoing acute haemolysis when exposed to 8‐aminoquinoline-based drugs, such as primaquine. For this reason it is imperative to identify individuals with G6PD deficiency prior to administering these anti-malarial drugs. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most commonly found human enzyme deficiency, affecting over 400 million people worldwide [1,2,3,4]. People who most need these drugs have a relatively high chance of carrying the G6PD deficiency trait, putting them at risk of adverse reactions
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