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

Abstract

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.

A Practical Approach to Screening for Strongyloides stercoralis

“…Serology is a more suitable screening method due to its high sensitivity (ranging from 85 to 90% depending on the manufacturing company); however, the specificity of serological tests is compromised, especially in endemic areas, by cross-reactivity with other tissue helminth infections. In addition, the sensitivity of serological tests may be reduced in immunosuppressed patients [6]. To reach optimal sensitivity, a combined approach of direct and indirect diagnostic methods is recommended [7], particularly for immunosuppressed or pre-immunosuppressed patients.…”

“…Serology is a useful and sensitive indirect method for the detection of strongyloidiasis in immunocompetent individuals. However, considering the lower sensitivity of serology in the case of ongoing immunosuppression [6,17], a lower serological cutoff value may be established for immunosuppressed patients. To our knowledge, only one published study has reported a different cutoff value for immunosuppressed patients [18], which cannot be generalized to the various commercial brands or to the in-house tests.…”

“…However, if this cannot be done, more realistically, a lone negative serology result might be considered to be doubtful in this situation. [6,17], a lower serological cutoff value may be established for immunosuppressed patients. To our knowledge, only one published study has reported a different cutoff value for immunosuppressed patients [18], which cannot be generalized to the various commercial brands or to the in-house tests.…”

“…It is important to point out that the prevalence map is based on an estimation; if a different local prevalence is known, this should guide the diagnostic decision. Repeated stool tests (up to three) are generally recommended to increase sensitivity, but this is often not performed because of logistical reasons; Baermann analysis should be performed within a short time after collection, and an interval of at least 72 h needs to be adhered to in between, making this unfeasible in the case of urgent immunosuppressive treatment [6]. If only a single stool sample is available, as is most often the case, our algorithm proposes assessment by stool PCR, KAPC and Baermann concentration in parallel, in order to increase the sensitivity of the diagnostic tests [4].…”

Holistic Approach to Tuberculosis Detection, Treatment and Prevention: Emerging Evidence and Strategies from the Field

“…Reactivation of latent tuberculosis infection (LTBI) or latent parasitic infection (LPI) during drug-induced immunosuppression can have serious consequences. Carnino et al [ 7 ] sought to determine the seroprevalence of LTBI and LPI in such patients at the Geneva University Hospitals in Switzerland and explore its relationship with country of origin or previous travel. They argue that screening before immunosuppressive therapy 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.…”