Abstract
G6PD deficiency is the most common human enzymopathy, particularly in individuals of African descent. Its epidemiology has not been studied in the Dominican Republic, where many individuals have African ancestry. HIV-infected patients are at risk for adverse effects from G6PD deficiency due to receiving prophylaxis with oxidative drugs, which can induce hemolysis in G6PD-deficient patients. We determined the prevalence of G6PD deficiency, as well as the spectrum of variants, in HIV-infected patients at the Clínica de Familia La Romana, a free HIV clinic in the Dominican Republic.
A medical history, chart review, and G6PD testing were performed for 238 consenting HIV-positive adults. A qualitative assay (Trinity Biotech), performed at the clinic, was assessed for color change at 30 and 60 minutes. All blood samples were also shipped to our home institution for quantifying enzyme activity (Trinity Biotech) and molecular testing by Sanger sequencing. The threshold for G6PD deficiency was 5.42 U/g hemoglobin (Hb; i.e. <60% of the mean normal activity level, by WHO criteria). Severe anemia was defined as Hb <8 g/dL. A history of hemolysis was defined as a report of dark urine or jaundice. Statistical analysis was performed using SAS 9.3.
The overall prevalence of G6PD deficiency was 8.8% and was similar in males (9.3% [9/97]) and females (8.5% [12/141]), but higher in Haitians (18% [9/50]) as compared to Dominicans (6.4% [12/187]; p=0.01), determined by maternal country of birth. All G6PD-deficient subjects carried the “African” variant (G6PD A-). ∼60% of patients had received and ∼15% were currently on trimethoprim-sulfamethoxazole (TMP-SMX), regardless of G6PD status. Two G6PD-normal patients received Dapsone after TMP-SMX was stopped for allergy or anemia. Univariate analysis identified variables associated with G6PD deficiency in this cohort. A multivariable logistic regression model identified three variables that predicted G6PD status (p<0.05): maternal country of birth (p=0.01), a history of hemolysis (p=0.01), and a history of severe anemia (p=0.03). Using these criteria for screening the cohort, we identified a subset of patients who would benefit most from qualitative G6PD testing. A stepwise screening strategy using clinical history and biochemical testing yielded a diagnostic sensitivity of 94.7% and specificity of 97.2%. In addition, using the combined approach, rather than biochemical testing alone, increased the pretest probability from 8.8% to 15.1% and halved the number of patients needing testing. This algorithm for diagnosing G6PD deficiency may be a cost-effective strategy for improving the quality of care for HIV-infected patients in resource-limited settings.
Screening for G6PD deficiency in the developing world is further complicated by lack of access to confirmatory testing. Detecting heterozygous females with intermediate, or even normal, G6PD activity is a diagnostic challenge for enzyme assays. To diagnose heterozygotes definitively, all G6PD exons were sequenced for all subjects with G6PD activity near or below the threshold, with discordant qualitative and quantitative Results, and for selected controls. Of 55 subjects sequenced, 29 had at least one G6PD A- allele. The G6PD A+ allele, also associated with African ancestry, was the only other variant detected. Overall, the 3 Methods agreed well when subjects had low or high G6PD activity, with uncertainty near the quantitative threshold for G6PD deficiency. The sequencing assay detected the G6PD A- allele in all subjects found to be G6PD-deficient by the quantitative assay, but also identified 8 heterozygous females with normal enzyme activity. The qualitative assay, whose sensitivity was increased by assessing color change at 30 minutes, was able to detect the majority (12/19) of heterozygous females, but 6 were heterozygotes with normal enzyme activity. Nonetheless, because genotype does not directly correlate with clinical severity, low activity remains the gold standard for diagnosing G6PD deficiency. Therefore, optimizing qualitative enzyme assays to detect biochemically deficient patients in conjunction with using clinical screening to increase pretest probability may together improve the diagnosis of clinically relevant G6PD deficiency in resource-limited settings.
Disclosures:
No relevant conflicts of interest to declare.
A HISTOCHEMICAL METHOD FOR THE DEMONSTRATION OF 20α-HYDROXYSTEROID DEHYDROGENASE ACTIVITY IN RAT OVARIES
