Background/Purpose:

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked genetic defect that causes a non-immune hemolytic anemia affecting more than 400 million people worldwide. When initiating medications with oxidant potential such as sulfasalazine (SSZ), patients are frequently tested for G6PD deficiency. The objectives of this study include determining the prevalence of G6PD deficiency among those tested and characterizing G6PD test ordering patterns.

Methods:

Retrospective chart review was performed using the electronic medical record at the VA Greater Los Angeles Healthcare System. The database was searched for all patients who had a G6PD test ordered between 2009-2014. Data collected included demographics, reasons G6PD testing was done, number of patients who underwent repeat testing, and the specialty of the provider who ordered the test. Prevalence of G6PD deficiency was determined. Descriptive analysis of categorical variables was done with the Chi-Square test. The odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the association between ethnicity and G6PD deficiency.

Results:

G6PD levels were measured in 737 patients. The study population included 661 males (89.7%) and 76 females (10.3%) with a mean age of 56.6 (± SD 14.9). There were 60 (8.1%) patients with G6PD deficiency. The percentage of patients with G6PD deficiency by gender and within each self-reported race/ethnicity was as follows: 8.4% (N=56) males, 5.3% (N=4) females, 18.2% (N=2) American Indian, 17.9% (N=47) African American, 7.7% (N=2) Asian, 2.5% (N=7) Caucasian, 1.1% (N=1) Hispanic, and 100% (N=1) Brazilian. Observed differences in G6PD deficiency prevalence were statistically significant based on gender and self-reported race/ethnicity (p<0.001 for both). Odds ratios were calculated to evaluate the association between race/ethnicity and G6PD deficiency: African American (OR 7.77, [95% CI 4.12-14.66]), American Indian (OR 2.56, [95% CI 0.54-12.12]), Asian (OR 0.94, [95% CI 0.22-4.07]), Caucasian (OR 0.20, [95% CI 0.09-0.45]), and Hispanic (OR 0.11, [95% CI 0.02-0.82]). Repeated testing was carried out in 105 (14.2%) patients. Reasons for G6PD testing included initiation of SSZ for inflammatory arthritis (52.3%), dapsone for PCP prophylaxis (14.2%), and anemia workup (11.1%). Rheumatology ordered the majority of repeat tests (60.7%) for the following reasons: SSZ (65), hydroxychloroquine initiation (1), anemia workup (4), and dapsone initiation (4).

Conclusion:

G6PD deficiency occurred in 8% of our study population, mainly in African Americans, American Indians, and Asians. Rheumatologists ordered most of the tests measuring G6PD levels primarily before considering SSZ therapy and were more likely to order duplicate tests when compared to other specialists. Unnecessary repeat testing is an issue that could be reduced with pop-up computer reminder. This study supports G6PD deficiency testing for high risk populations, including African Americans, American Indians, and Asians, but routine screening of all rheumatology patients for G6PD deficiency when considering SSZ therapy may not be needed.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/glucose-6-phosphate-dehydrogenase-testing-in-a-us-veterans-healthcare-system-are-we-ordering-unnecessary-tests/