ABSTRACT:

Background/Purpose: Glucose 6 Phosphate Dehydrogenase (G6PD) deficiency is the most common enzymatic disorder of red blood cells, and its frequency varies among different ethnicities. People with G6PD deficiency may develop hemolytic anemia with certain drugs such as hydroxychloroquine, sulfasalazine and dapsone. Clinically, there is inconsistent practice in testing G6PD level among rheumatologists before initiating drugs like hydroxychloroquine, and there are no set guidelines on testing the enzyme. G6PD deficiency occurs in 0.5-7% in Americans, and its frequency in patients with rheumatic diseases was not previously reported in America. This study aimed at determining the frequency of G6PD deficiency in the disease population.

Methods: This study is a retrospective chart review and was approved by the Institutional Research Board.  Electronic Medical Records (EMRs) were reviewed of patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren Syndrome, and seronegative spondyloarthritis between July 2013 and December 2016. These patients could be tested for G6PD due to concern for anemia from potential use of the above drugs.  Patients aged 18 and older were included, and their demographics, rheumatic diseases, the medication use and G6PD testing results were recorded. G6PD deficiency was considered to be present if its value was less than 7.0-20.5 U/g. Descriptive statistics and chi-square/fisher exact tests were used for the data analysis.  

Results: Eighty-nine (39%) of 228 patients with rheumatic diseases were screened for G6PD deficiency. In the 89 patients tested, 7 patients (7.9%) including 5 females and 2 males were found to be G6PD deficient. Their mean age was 34.9 years, and there were 5 (71%) Caucasians and 2(29%) African Americans. Overall, the frequency of G6PD deficiency in patients with rheumatic diseases was close to that in the general American population. Caucasians patients had a frequency of 5.6%, and this may be due to higher Caucasians tested in our study. Demographics and relevant data in patients with G6PD tested and those with G6PD deficiency are shown in Table. The overwhelming majority of the patients tested were treated with hydroxychloroquine. G6PD deficiency is an x-linked disease, mainly affects male, and should be considered in female as well. There was a higher percentage of females with G6PD deficiency than males in this study as the disease population tested consisted of 97% of female patients.

    Table 1 Demographics and Relevant Data in Patients with G6PD Tested and Those with Deficiency

Conclusion: This may be the first study to examine the frequency of G6PD deficiency in the American patient population with rheumatic diseases. Such testing might not be cost effective given the low incidence of G6PD deficiency in the patient population. Instead, we recommend to monitor for potential anemia with complete blood counts in the setting of hydroxychloroquine use.