Evaluation of molecular and serological testing for imported urogenital schistosomiasis screening in a referral tropical medicine centre in Barcelona, Spain.

Abstract

Background: Schistosomiasis, a major neglected tropical disease, is caused by Schistosoma spp. It is estimated that more than 200 million people are affected worldwide, mostly in Africa. The gold standard diagnosis of urogenital schistosomiasis (UGS) is the microscopic visualisation of Schistosoma haematobium eggs in concentrated urine; however, its sensitivity is low. This study aimed to evaluate the effectiveness of molecular and serological testing for imported UGS screening in asymptomatic sub-Saharan migrants in a non-endemic setting.

Methods: A retrospective cross-sectional study between November 2021 and December 2022 was conducted by collecting demographic, clinical and laboratory data from the medical records of migrants from endemic areas screened for UGS at the International Health Unit Vall d'Hebron-Drassanes, Barcelona, Spain. Urine samples were analysed by real-time PCR for S. haematobium DNA and by microscopy for egg detection. Serum samples were tested using a serological assay based on enzyme-linked immunosorbent assay (ELISA). UGS was confirmed by a positive result in real-time PCR and/or microscopy, while possible UGS was defined as a case with only a positive serological result.

Results: A total of 604 patients were included in this study; 32 out of 604 (5.3%) urine samples were positive for S. haematobium by real-time PCR and/or microscopy examination (confirmed UGS cases). Schistosoma haematobium DNA was detected in 28/604 (4.6%) urine samples, while eggs were visualised in 24/604 (3.9%), with 12 discordant cases between both techniques. Real-time PCR demonstrated a sensitivity of 83.3%, a specificity of 98.6%, and a kappa value of 0.76. Serology was performed in 529/604 cases and exhibited lower specificity, 70.87% (kappa value 0.26). Other laboratory parameters such as leukocyturia, microhaematuria, eosinophilia and elevated IgE were significantly associated with UGS diagnosis.

Conclusions: Real-time PCR proved to be more sensitive than microscopy for diagnosing imported UGS in non-endemic settings, with minimal discordance between methods. The serological test exhibited very low specificity and high sensitivity rates, suggesting its usefulness as a screening test among high-risk populations in non-endemic settings.