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

Sampa Pal,Richard Ansbro,Amanda Hann,Pooja Bansil,Jane Myburgh,Lynn Robertson,Mark Layton,Sean C Murphy,Michelle R Manis,Gonzalo J Domingo,Nickolas A Styke,Vajra Allan,Stephanie Zobrist,Tobi Akingbade,Gwen Ambler,Andrew Bryan,Maria Kahn,James G Kublin,Emily Gerth‐Guyette ,Greg T Bizilj

doi:10.1371/journal.pone.0257560

Abstract

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.

Highlights

Glucose-6-phosphate dehydrogenase (G6PD) (EC 1.1.1.49) is an essential enzyme in the pentose phosphate metabolic pathway
Three of the studies were performed on adult volunteers in the United States to assess the performance of the STANDARDTM G6PD Test (SD BIOSENSOR, South Korea) on fresh fingerstick blood: 1. A prospective, cross-sectional diagnostic accuracy study recruiting adults presenting to the Plasma MedResearch clinical laboratory in Boca Raton, Florida, USA
For the fingerstick studies conducted in the United States, recruitment focused primarily on African Americans to maximize the probability of recruiting individuals with G6PD deficiency

Summary

Introduction

Glucose-6-phosphate dehydrogenase (G6PD) (EC 1.1.1.49) is an essential enzyme in the pentose phosphate metabolic pathway. It helps maintain the levels of the co-enzyme nicotinamide adenine dinucleotide phosphate, and through this, glutathione. The X-linked G6PD gene is highly polymorphic with several missense mutations, resulting in enzyme with reduced activity or more often reduced stability. These mutations result in higher proportions of red blood cells with suboptimal amounts of the enzyme and more susceptibility to lysis when exposed to an oxidative challenge [1, 2]. An estimated 400 million people have G6PD deficiency, a large proportion of whom reside in malaria-endemic regions [2, 3]

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Results

Conclusion