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CDC and UNICEF mention the Crystal VC® dipstick rapid test and WHO says it "is currently in the process of validating" this new rapid diagnostic test (RDT).

Quote from CDC - https://www.cdc.gov/cholera/diagnosis.html:

In areas with limited to no laboratory testing, the Crystal VC® dipstick rapid test can provide an early warning to public health officials that an outbreak of cholera is occurring. However, the sensitivity and specificity of this test is not optimal. Therefore, it is recommended that fecal specimens that test positive for V. cholerae O1 and/or O139 by the Crystal VC® dipstick be confirmed using traditional culture-based methods suitable for the isolation and identification of V. cholerae.

Quote from the UNICEF Cholera Toolkit 2013 - https://www.unicef.org/cholera/Cholera-Toolkit-2013.pdf

Rapid diagnostic tests (RDT)

A rapid diagnostic test (RDT) provides important complementary information that, when combined with clinical and epidemiologic information, can further support or oppose the suspicions that an outbreak is due to cholera, especially when awaiting confirmation from stool cultures. RDT’s for cholera do not require an equipped laboratory, and they can be performed in field conditions or in any clinic. However, they are not 100% specific, and provide no isolates for antimicrobial susceptibility testing, serotyping, toxin testing or molecular subtyping.

The Crystal VCR RDT for V. cholerae O1 and O139 can provide results in about 10 minutes. It can be used to detect outbreaks early in their course, if procured and distributed to all levels of the national health system. It is relatively inexpensive (approximately $2 per test) and easy to use (even by those with limited technical skills) with appropriate instructions.

However, RDTs are not particularly useful for making the diagnosis of cholera in a single patient. The greater the number of patients tested, the more confidence one can have in the results of the RDTs, which will either show a majority of cholera-positive or a majority of cholera- negative results.

For example, using the Crystal VCR RDT for a cluster of cases:

• If the cause of their disease is cholera, the test will be positive in about 8 or 9 of the ten tests (sensitivity = 80-90%). • If the cluster of cases is due to another disease, the RDT will be negative in most instances (at least 6 out of 10, and probably more) (specificity > 60%).

Because of its potential usefulness, the Crystal VC RDT and locally adapted instructions or guidelines for its appropriate use should probably be part of the supply package distributed in advance of an outbreak in areas where outbreaks are predictable occurrences.