Abstract
SummaryBackgroundCryptosporidiosis is a common cause of diarrhoea in young children (aged younger than 24 months) in low-resource settings but is currently challenging to diagnose. Light-emitting diode fluorescence microscopy with auramine-phenol staining (LED-AP), recommended for tuberculosis testing, can also detect Cryptosporidium species. A lateral-flow test not requiring refrigerator storage (by contrast with most immunochromatographic lateral-flow assays) has also recently been developed for Cryptosporidium spp detection. We aimed to evaluate the diagnostic accuracy and operational feasibility of LED-AP and the lateral-flow test strip for cryptosporidiosis in children.MethodsWe did a prospective diagnostic accuracy study in two health-care facilities in Ethiopia, in a consecutive series of children younger than 5 years of age with diarrhoea (three or more loose stools within the previous 24 h) or dysentery (at least one loose stool with stains of blood within the previous 24 h). Stool samples were tested for Cryptosporidium spp by LED-AP and the lateral-flow test strip; accuracy of each test was estimated by independent and blind comparison with a composite reference standard comprising quantitative immunofluorescent antibody test (qIFAT), ELISA, and quantitative PCR (qPCR). Quantitative cutoff values for diarrhoea-associated infection were established in an embedded case-control substudy, with cases of cryptosporidiosis coming from the 15 districts in and around Jimma and the eight districts surrounding Serbo, and community controls without diarrhoea in the previous 48 h recruited by weekly frequency matching by geographical district of the household, age group, and enrolment week.FindingsStool samples from 912 children with diarrhoea or dysentery and 706 controls from the case-control substudy were tested between Dec 22, 2016, and July 6, 2018. Estimated reference-standard cutoff values for cryptosporidiosis positivity were 2·3 × 105 DNA copies per g of wet stool for qPCR, and 725 oocysts per g for qIFAT. LED-AP had a sensitivity for cryptosporidiosis of 88% (95% CI 79–94; 66 of 75 samples) and a specificity of 99% (98–99; 717 of 726 samples); the lateral-flow test strip had a sensitivity of 89% (79–94; 63 of 71 samples) and a specificity of 99% (97–99; 626 of 635 samples).InterpretationLED-AP has high sensitivity and specificity for cryptosporidiosis and should be considered as a dual-use technology that can be easily integrated with existing laboratory infrastructures in low-resource settings. The lateral-flow test strip has similar sensitivity and specificity and provides an alternative that does not require microscopy, although purchase cost of the test strip is unknown as it is not yet available on the market.FundingNorwegian Research Council GLOBVAC fund, The Bill & Melinda Gates Foundation, Norwegian Society for Medical Microbiology, University of Bergen, and Vestfold Hospital Trust.
Highlights
Cryptosporidiosis is the fifth leading cause of diarrhoeal mortality worldwide and caused more than 48 000 deaths and led to a loss of 12·9 million disability-adjusted lifeyears in 2016, with the highest burden in sub-Saharan Africa.[1]
Increased effort has been put into developing better drugs for cryptosporidiosis,[6] but a test-and-treat strategy will require a rapid, lowtechnology, reliable, and affordable diagnostic test that can be used near the point of care, and that is suitable for use in low-resource settings.[7]
Added value of this study We evaluated the diagnostic accuracy of two simple tests for cryptosporidiosis in children in a low-income country, and included cost-per-test calculations and operational assessment
Summary
Cryptosporidiosis is the fifth leading cause of diarrhoeal mortality worldwide and caused more than 48 000 deaths and led to a loss of 12·9 million disability-adjusted lifeyears in 2016, with the highest burden in sub-Saharan Africa.[1] The disease ranked among the top five causes of diarrhoea in the Global Enteric Multicenter Study in 2007–11,2,3 and has probably increased in relative impor tance since the rotavirus vaccine was rolled out globally.[4] There is no vaccine against Cryptosporidium species and the only approved drug, nitazoxanide, has moderate effect on diarrhoea and parasite clearance; the drug significantly reduced mortality in one trial, it is not effective in children with HIV.[5] Increased effort has been put into developing better drugs for cryptosporidiosis,[6] but a test-and-treat strategy will require a rapid, lowtechnology, reliable, and affordable diagnostic test that can be used near the point of care, and that is suitable for use in low-resource settings.[7] Diagnostic accuracy evaluations that are not done in the relevant clinical setting over estimate diagnostic accuracy and field applicability.[8] We identified only one study from east Africa that evaluated immunochromatographic lateral-flow assays (ICLFs) in children with complicated severe acute malnutrition, reporting moderate sensitivity against PCR results,[9] and a Turkish study that evaluated modified Ziehl-Neelsen www.thelancet.com/infection Vol 21 May 2021
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