title: Tools for mass screening of G6PD deficiency: validation of the WST8/1-methoxy-PMS enzymatic assay in Uganda.
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.
authors.affiliation: Malaria Centre, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Mariana
authors.initials: M
authors.lastname: De Niz
authors.forename: Alice C
authors.initials: AC
authors.lastname: Eziefula
authors.forename: Lucas
authors.initials: L
authors.lastname: Othieno
authors.forename: Edith
authors.initials: E
authors.lastname: Mbabazi
authors.forename: Damalie
authors.initials: D
authors.lastname: Nabukeera
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Ssemmondo
authors.forename: Samuel
authors.initials: S
authors.lastname: Gonahasa
authors.forename: Patrick
authors.initials: P
authors.lastname: Tumwebaze
authors.forename: Deborah
authors.initials: D
authors.lastname: Diliberto
authors.forename: Catherine
authors.initials: C
authors.lastname: Maiteki-Sebuguzi
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Staedke
authors.forename: Chris
authors.initials: C
authors.lastname: Drakeley
mesh_terms: D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000379:methods*; D015331:Cohort Studies; D057075:Enzyme Assays / Q000379:methods*; D005260:Female; D005955:Glucosephosphate Dehydrogenase Deficiency / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008403:Mass Screening / Q000379:methods*; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D014454:Uganda