Is folate deficiency a common cause of distal symmetric polyneuropathy in Zambian clinics?

Objectives: To evaluate the odds of vitamin B12 and folate deficiencies among Zambian clinic attendees with distal symmetric polyneuropathy (DSP) and age, sex, and HIV matched controls.

Methods: Cases were adults from clinics in urban/peri-urban Zambia. Controls were enrolled among persons not seeking personal medical care, such as a caregiver or person collecting antiretrovirals without a medical complaint. Participants underwent structured interviews, physician examination, and assessments of complete blood count, renal and liver profiles, serum vitamin B12 and folate, erythrocyte folate, plasma total homocysteine and methylmalonic acid. HIV testing and CD4 counts were performed when appropriate.

Results: Among 107 consenting matched case-control pairs, 65% were female, 52% HIV positive, with mean age of 47.6 (SD 13.5) years. Among HIV positive participants, mean CD4 count was 484 (SD 221) and 482 (SD 236) for cases and controls, respectively (p = .93). DSP symptoms and severity did not differ by HIV status (p's > 0.05). Height, history of tuberculosis treatment, alcohol use, education, asset index, dietary diversity, and nutritional supplement use did not differ between cases and controls (p's > 0.05). DSP cases had at least 3:1 odds of having low serum folate (p = .0001), severely low erythrocyte folate (p = .014), and elevated total homocysteine (p = .001) levels compared to controls. Markers of vitamin B12 deficiency were not associated with case status (p's > 0.05).

Conclusion: Markers of folate deficiency are highly associated with DSP among Zambian clinic attendees. Future studies should consider a broader range of comorbid nutritional deficiencies, and strategies for interventions.