Leprosy in blood donors.

Objectives: We investigated the prevalence of anti-phenolic glycolipid-I (PGL-I) IgM antibodies among temporarily unfit blood donors at the Pará State Blood Bank (HEMOPA), located in the Amazon region of northern Brazil. Using an arbitrary high cutoff for optical density (OD ≥0.750) in ELISA, a subset of donors was invited for clinical evaluation for leprosy.

Methods: Temporarily unfit individuals were invited to participate, and blood samples were collected for anti-PGL-I IgM titration by ELISA. Donors with high OD values were referred for clinical examination, slit skin smear (SSS) bacilloscopy, and quantitative PCR (qPCR) targeting M. leprae-specific repetitive element (RLEP) sequences from dermal scrapes of the earlobes and peripheral blood.

Results: From an annual average of 2762 temporarily unfit donors (2019-2023), 500 (16.6%) were tested for anti-PGL-I IgM. Of these, 20/500 (4.0%) had high antibody titres, and 8/20 (40.0%) attended clinical evaluation, resulting in 5/8 (62.5%) newly diagnosed cases of leprosy. Among these, Mycobacterium leprae detection yielded positivity rates of 2/8 (25.0%) by SSS bacilloscopy, 3/7 (42.9%) by qPCR of dermal scrapes, and 2/8 (25.0%) by qPCR of peripheral blood.

Conclusions: Using an anti-PGL-I IgM cutoff of OD ≥0.750, we identified a significant proportion of undiagnosed leprosy cases among temporarily unfit blood donors. These findings support the need for targeted leprosy screening in this population. Regardless of qPCR results, individuals with clinical signs of leprosy require appropriate treatment and assessment of their eligibility for blood donation.