Screening for Parasitic Infection and Tuberculosis in Immunosuppressed and Pre-Immunosuppressed Patients: An Observational Study

Reactivation of latent tuberculosis infection (LTBI) or latent parasitic infection (LPI) during drug-induced immunosuppression can have serious consequences. The Division of tropical and humanitarian medicine of the Geneva University Hospitals runs a specific consultation for parasitic screening of immunosuppressed or pre-immunosuppressed patients. We sought to determine the seroprevalence of LTBI and LPI in such patients and explore its relationship with country of origin or previous travel in a retrospective, single-centre observational study from 2016 to 2019. Demographic data, travel history, ongoing treatments and results of the parasitological (Strongyloides stercoralis, Trypanosoma cruzi, Echinococcus multilocularis, Entamoeba histolytica and Leishmania spp.) and TB screening were collected to calculate LPI or LTBI prevalence. Risk factors for LTBI and strongyloidiasis were analysed using Poisson regression with robust variance. Among 406 eligible patients, 24/353 (6.8%) had LTBI, 8/368 (2.2%) were positive for Strongyloides stercoralis infection, 1/32 (3.1%) was positive for Entamoeba histolytica and 1/299 (0.3%) was positive for Leishmaniasis. No cases of Trypanosoma cruzi (0/274) or Echinococcus multilocularis (0/56) infection were detected. Previous travel to or originating from high-prevalence countries was a risk factor for LTBI (PR = 3.4, CI 95%: 1.4–8.2 and 4.0, CI 95%: 1.8–8.9, respectively). The prevalence of serological Strongyloidiasis in immunosuppressed patients is lower in comparison to those without immunosuppression (PR = 0.1, CI 95%: 0.01–0.8). In conclusion, screening before immunosuppression needs to be individualized, and LTBI and LPI need to be ruled out in patients who originate from or have travelled to high-prevalence countries. The sensitivity of strongyloidiasis serology is reduced following immunosuppression, so an algorithm combining different tests or presumptive treatment should be considered.