Tools for mass screening of G6PD deficiency: Validation of the WST8/1-methoxy-PMS enzymatic assay in Uganda

Mariana De Niz, Alice C. Eziefula, Lucas Othieno, Edith Mbabazi, Damalie Nabukeera, Emmanuel Ssemmondo, Samuel Gonahasa, Patrick Tumwebaze, Deborah Diliberto, Catherine Maiteki-Sebuguzi, Sarah G. Staedke, Chris Drakeley*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Background: The distribution of the enzymopathy glucose-6-phosphate dehydrogenase (G6PD) deficiency is linked to areas of high malaria endemicity due to its association with protection from disease. G6PD deficiency is also identified as the cause of severe haemolysis following administration of the anti-malarial drug primaquine and further use of this drug will likely require identification of G6PD deficiency on a population level. Current conventional methods for G6PD screening have various disadvantages for field use. Methods. The WST8/1-methoxy PMS method, recently adapted for field use, was validated using a gold standard enzymatic assay (R&D Diagnostics Ltd ®) in a study involving 235 children under five years of age, who were recruited by random selection from a cohort study in Tororo, Uganda. Blood spots were collected by finger-prick onto filter paper at routine visits, and G6PD activity was determined by both tests. Performance of the WST8/1-methoxy PMS test under various temperature, light, and storage conditions was evaluated. Results: The WST8/1-methoxy PMS assay was found to have 72% sensitivity and 98% specificity when compared to the commercial enzymatic assay and the AUC was 0.904, suggesting good agreement. Misclassifications were at borderline values of G6PD activity between mild and normal levels, or related to outlier haemoglobin values (<8.0 gHb/dl or >14 gHb/dl) associated with ongoing anaemia or recent haemolytic crises. Although severe G6PD deficiency was not found in the area, the test enabled identification of low G6PD activity. The assay was found to be highly robust for field use; showing less light sensitivity, good performance over a wide temperature range, and good capacity for medium-to-long term storage. Conclusions: The WST8/1-methoxy PMS assay was comparable to the currently used standard enzymatic test, and offers advantages in terms of cost, storage, portability and use in resource-limited settings. Such features make this test a potential key tool for deployment in the field for point of care assessment prior to primaquine administration in malaria-endemic areas. As with other G6PD tests, outlier haemoglobin levels may confound G6PD level estimation.

Original languageEnglish (US)
Article number210
JournalMalaria journal
Volume12
Issue number1
DOIs
StatePublished - 2013

Funding

We would like to express our gratitude to the Infectious Disease Research Collaboration, and the ACT PRIME and Tororo lab teams, particularly Florence Nankya, Rita Kabuleta Luswata, Joseph Wadamba, and Andrew Walakira for their contributions to the logistics of this study. We thank Eric Becha and Simon P. Kigozi for advice on data analysis. We are very grateful to all participants and their families. We thank James McCarthy and Melissa Kuwahata, and George Reclos for their advice on the use of the WST8/1-methoxy PMS test and the R&D reference tests respectively. ACE and CD are supported by a grant from the Wellcome Trust (090558 & 091924 respectively). MDN was supported by an LSHTM grant to carry out this study. The ACT PRIME study was supported by the ACT Consortium, which is funded through a grant from the Bill and Melinda Gates Foundation to the London School of Hygiene & Tropical Medicine. This research was previously presented at the 2012 ‘Challenges in Malaria Research, Progress towards elimination’ meeting in Basel, Switzerland.

Keywords

  • G6PD deficiency
  • Malaria
  • Primaquine
  • WST8/1-methoxy PMS

ASJC Scopus subject areas

  • Infectious Diseases
  • Parasitology

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