Abstract
BackgroundThe diagnosis of cystic echinococcosis (CE) is based primarily on imaging, in particular with ultrasound for abdominal CE, complemented by serology when imaging results are unclear. In rural endemic areas, where expertise in ultrasound may be scant and conventional serology techniques are unavailable due to lack of laboratory equipment, Rapid Diagnostic Tests (RDTs) are appealing.Methodology/Principal FindingsWe evaluated the diagnostic accuracy of 3 commercial RDTs for the diagnosis of hepatic CE. Sera from 59 patients with single hepatic CE cysts in well-defined ultrasound stages (gold standard) and 25 patients with non-parasitic cysts were analyzed by RDTs VIRapid HYDATIDOSIS (Vircell, Spain), Echinococcus DIGFA (Unibiotest, China), ADAMU-CE (ICST, Japan), and by RIDASCREEN Echinococcus IgG ELISA (R-Biopharm, Germany). Sensitivity, specificity and ROC curves were compared with McNemar and t-test. For VIRapid and DIGFA, correlation between semiquantitative results and ELISA OD values were evaluated by Spearman’s coefficient. Reproducibility was assessed on 16 randomly selected sera with Cohen’s Kappa coefficient. Sensitivity and Specificity of VIRapid (74%, 96%) and ADAMU-CE (57%, 100%) did not differ from ELISA (69%, 96%) while DIGFA (72%, 72%) did (p = 0.045). ADAMU-CE was significantly less sensitive in the diagnosis of active cysts (p = 0.019) while DIGFA was significantly less specific (p = 0.014) compared to ELISA. All tests were poorly sensitive in diagnosing inactive cysts (33.3% ELISA and ADAMU-CE, 42.8% DIGFA, 47.6% VIRapid). The reproducibility of all RDTs was good-very good. Band intensity of VIRapid and DIGFA correlated with ELISA OD values (r = 0.76 and r = 0.79 respectively, p<0.001).Conclusions/SignificanceRDTs may be useful in resource-poor settings to complement ultrasound diagnosis of CE in uncertain cases. VIRapid test appears to perform best among the examined kits, but all tests are poorly sensitive in the presence of inactive cysts, which may pose problems with accurate diagnosis.
Highlights
Cystic echinococcosis (CE) is a parasitic zoonosis caused by the larval stage of the dog tapeworm Echinococcus granulosus complex
We evaluated the diagnostic performance of three Rapid Diagnostic Tests (RDTs) and compared them with a commercial ELISA test routinely used in our diagnostic laboratory
Our results show that RDTs have overall comparable performances to ELISA in the diagnosis of hepatic CE in well-defined stages, significant differences exist among them
Summary
Cystic echinococcosis (CE) is a parasitic zoonosis caused by the larval stage of the dog tapeworm Echinococcus granulosus complex. The parasite is transmitted between canids (definitive hosts harboring in the intestine the adult stage of the tapeworm), and livestock, sheep (intermediate hosts becoming infected by fecal-oral route with eggs shed with dog feces). The larval stage develops as an expanding fluid-filled cyst, which can infect the definitive host eating infected organs. Humans behave as accidental intermediate hosts, where CE cysts develop mostly in the liver, followed by lungs. The infection is prevalent worldwide especially in rural livestock-raising areas such as the Mediterranean, Eastern Europe, North and East Africa, South America, Central Asia, China and Australia. The diagnosis of cystic echinococcosis (CE) is based primarily on imaging, in particular with ultrasound for abdominal CE, complemented by serology when imaging results are unclear. In rural endemic areas, where expertise in ultrasound may be scant and conventional serology techniques are unavailable due to lack of laboratory equipment, Rapid Diagnostic Tests (RDTs) are appealing
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