The Laboratory Diagnosis and Follow Up of Strongyloidiasis: A Systematic Review

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Abstract
Strongyloidiasis is frequently under diagnosed since many infections remain asymptomatic and conventional diagnostic tests based on parasitological examination are not sufficiently sensitive. Serology is useful but is still only available in reference laboratories. The need for improved diagnostic tests in terms of sensitivity and specificity is clear, particularly in immunocompromised patients or candidates to immunosuppressive treatments. This review aims to evaluate both conventional and novel techniques for the diagnosis of strongyloidiasis as well as available cure markers for this parasitic infection. The search strategy was based on the data-base sources MEDLINE, Cochrane Library Register for systematic review, EmBase, Global Health and LILACS and was limited in the search string to articles published from 1960 to August 2012 and to English, Spanish, French, Portuguese and German languages. Case reports, case series and animal studies were excluded. 2003 potentially relevant citations were selected for retrieval, of which 1649 were selected for review of the 143 were eligible for final inclusion. Sensitivity of microscopic-based techniques is not good enough, particularly in chronic infections. Furthermore, techniques such as Baermann or agar plate culture are cumbersome and time-consuming and several specimens should be collected on different days to improve the detection rate. Serology is a useful tool but it might overestimate the prevalence of disease due to cross-reactivity with other nematode infections and its difficulty distinguishing recent from past (and cured) infections. To evaluate treatment efficacy is still a major concern because direct parasitological methods might overestimate it and the serology has not yet been well evaluated; even if there is a decline in antibody titres after treatment, it is slow and it needs to be done at 6 to 12 months after treatment which can cause a substantial loss to follow-up in a clinical trial. Strongyloidiasis is a parasitic infection that can occur in any place of the world. It is not easy to diagnose because the conventional tests are not good enough, especially in individuals that do not present any symptoms of the disease. This is of particular importance in immunocompromised patients, because the disease can spread causing a disseminated disease which can be fatal. In this study, authors review both conventional and novel techniques for the diagnosis of strongyloidiasis. Parasitological examinations based on the detection of the parasite in faeces are the most common techniques used until now in the majority of laboratories. However, they have some disadvantages because most of the best techniques are cumbersome and time consuming and several stool samples have to be collected to improve the diagnosis. New techniques such as the serology which is performed through a blood test are becoming available, but they have still some problems; the test sometimes does not accurately differentiate strongyloidiasis from other helminthic diseases. Another major problem in this disease is to evaluate if patient is cured after the treatment. Parasitological methods can fail to detect treatment failure, and serology has not yet been well evaluated in this context.

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