Cholera diagnostic test evaluations needed

TDR news item
17 October 2012

Five commercially available rapid diagnostic tests (RDTs) for cholera show promise for use in field conditions, but need further study. This is the recommendation from a newly published review that took the first step in assessing developments in commercialised diagnostic tools. The authors recommend an independent assessment of these products, including technical improvements and production to trigger early detection of cholera epidemics. They also say that stringent standardization is needed to evaluate these and more tests.

Field and laboratory studies were performed in a wide range of settings demonstrating variability in performance. Only a few of the studies were sufficiently stringent, highlighting five RDTs that showed promise in field conditions; COAT, IP cholera dipstick, SMART, IP dipstick and Medicos.

Diagnosing cholera early at the onset of an epidemic, at the field level, should allow for a more timely response and a quick containment of the spread. Currently the gold standard to identify the bacteria, Vibrio cholerae, from patient samples relies on lengthy bacterial cultures, an array of biochemical tests, highly-skilled operators and numerous laboratory resources, few of which are available in remote locations. Research to develop more appropriate tools has largely focused on rapid diagnostic tests and attempts to simplify existing technologies, but no tests have undergone appropriate scrutiny to provide the evidence to make fully informed decisions on the efficacy of the tests.

The study authors, which include two TDR staff, took the first step by assessing developments in commercialised diagnostic tools, reviewing 14 previous evaluations of the 24 tests developed for the detection of Vibrio cholerae in human faecal samples since 1990. Rapid chromatographic-immuno assays (CIA) feature strongly. Polymerase chain reaction (PCR) assays maintain the ability to detect the lowest amount of bacteria; however CIAs achieve both low detection thresholds and high sensitivity and specificity, making them possible candidates for use in field conditions.

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Francis Moussy