Background: The clinical and laboratory characterization of Strongyloides stercoralis infection at diagnosis and after treatment is still poorly defined.

Objectives: The primary objective was to describe the pattern and frequency of clinical and laboratory characteristics associated with S. stercoralis infection. The secondary objectives were (a) comparison of characteristics reported in endemic versus non-endemic areas; and (b) the evaluation of the resolution of identified characteristics after treatment.

Methods: We searched PubMed, EMBASE, LILACS and CENTRAL up to May 2021. Eligible studies were randomized controlled trials (RCTs) for the treatment of S. stercoralis infection and prospective observational studies reporting data on symptoms caused by strongyloidiasis in individuals diagnosed with a highly specific test. Quality assessment was performed to assess the risk of bias. Demographic and clinical data were summarized using descriptive statistics. Meta-analysis was done by pooling the proportion of participants with symptoms with random effects model.

Results: Twenty studies were included: nine RCTs and 13 observational studies. Overall, symptoms were reported in 50.4% cases (95% CI 47.6-53.1), and were more often reported in non-endemic (58.6%, 95% CI 55.0-62.2) than in endemic (35.7%, 95% CI 31.4-39.9) areas. The removal of an article of lower quality did not impact on figures. Frequency of symptoms tended to reduce after treatment. Three studies reported the proportion of participants with eosinophilia before and after treatment: 76.9% of participants (95% CI 73.4-80.4) had eosinophilia at diagnosis, reducing to 27.4% (95% CI 24.0-30.7) after treatment.

Conclusions: About half of infected people complain at least of one symptom and almost 70% have eosinophilia. The frequency of symptoms and eosinophilia decreased after treatment, though the association with cure is not clearly defined. Providing relief from symptoms and eosinophilia is another reason, in addition to prevention of disseminated disease, for promoting screening and treatment of individuals with strongyloidiasis.