Abstract
BackgroundSchistosomiasis is a neglected infection affecting millions of people, mostly living in sub-Saharan Africa. Morbidity and mortality due to chronic infection are relevant, although schistosomiasis is often clinically silent. Different diagnostic tests have been implemented in order to improve screening and diagnosis, that traditionally rely on parasitological tests with low sensitivity. Aim of this study was to evaluate the accuracy of different tests for the screening of schistosomiasis in African migrants, in a non endemic setting.Methodology/Principal findingsA retrospective study was conducted on 373 patients screened at the Centre for Tropical Diseases (CTD) in Negrar, Verona, Italy. Biological samples were tested with: stool/urine microscopy, Circulating Cathodic Antigen (CCA) dipstick test, ELISA, Western blot, immune-chromatographic test (ICT). Test accuracy and predictive values of the immunological tests were assessed primarily on the basis of the results of microscopy (primary reference standard): ICT and WB resulted the test with highest sensitivity (94% and 92%, respectively), with a high NPV (98%). CCA showed the highest specificity (93%), but low sensitivity (48%). The analysis was conducted also using a composite reference standard, CRS (patients classified as infected in case of positive microscopy and/or at least 2 concordant positive immunological tests) and Latent Class Analysis (LCA). The latter two models demonstrated excellent agreement (Cohen’s kappa: 0.92) for the classification of the results. In fact, they both confirmed ICT as the test with the highest sensitivity (96%) and NPV (97%), moreover PPV was reasonably good (78% and 72% according to CRS and LCA, respectively). ELISA resulted the most specific immunological test (over 99%). The ICT appears to be a suitable screening test, even when used alone.ConclusionsThe rapid test ICT was the most sensitive test, with the potential of being used as a single screening test for African migrants.
Highlights
Schistosomiasis is a fluke worm infection affecting at least 78 countries and more than 200 million people worldwide, and causing an estimated burden of 3.3 million disability-adjusted lifeyears (DALYs) [1,2].Ninety-three percent of the global cases occur in sub-Saharan Africa, mostly caused by the species Schistosoma mansoni and S. haematobium
As in chronic infections eggs of both species are often missed by microscopy of faeces and urine, with this retrospective study we evaluate the accuracy of different, alternative diagnostic tests, for the screening of schistosomiasis in African migrants and asylum seekers, of whom many thousands reach the Italian coast every year proceding from the most endemic areas
Given the severe complications related to both S. mansoni and S. haematobium [8,9,10,11,12], and the availability of an effective and relatively inexpensive treatment [1,13,14], adequate protocols for screening and treatment of migrants are required
Summary
Schistosomiasis is a fluke worm infection affecting at least 78 countries and more than 200 million people worldwide, and causing an estimated burden of 3.3 million disability-adjusted lifeyears (DALYs) [1,2]. Ninety-three percent of the global cases occur in sub-Saharan Africa, mostly caused by the species Schistosoma mansoni and S. haematobium. In this area, approximately 300,000 deaths due to schistosomiasis are estimated annually [3,4,5,6]. Schistosomiasis, often clinically silent, is not routinely screened. Morbidity and mortality due to chronic infection are relevant, schistosomiasis is often clinically silent. Aim of this study was to evaluate the accuracy of different tests for the screening of schistosomiasis in African migrants, in a non endemic setting
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