Cholera diagnosis in human stool and detection in water: protocol for a systematic review of available technologies

Enhancing national cholera surveillance using rapid diagnostic tests (RDTs): A mixed methods evaluation

Cholera rapid diagnostic tests (RDTs) can strengthen existing surveillance systems by offering a cost-effective screening method that improves understanding of cholera burden allowing for targeted prevention and control efforts. The RDT Implementation Strategy and Evaluation (RISE) project is the pilot study for Gavi's innovative Diagnostic Procurement Platform which provides cholera RDTs to enhance national surveillance. Implementation of cholera RDTs was evaluated following their distribution in 2023 to facilities within Nepal's Early Warning and Reporting System (EWARS). Quantitative data was collected through EWARS surveillance reports, national-level and individual-level REDCap surveys from select facilities in Kathmandu. Key-informant interviews were also conducted in Kathmandu with personnel involved in cholera surveillance and response. Interviews were conducted using a semi-structured interview guide and analyzed according to inductively identified themes. Qualitative findings indicated generally positive perceptions of cholera RDTs, highlighting their speed and ease of use, and suitability for deployment in under-resourced areas by unskilled personnel. However, a lack of awareness of the RDTs, limited training, and concerns about the RDTs' quality, availability, and costs were challenges raised consistently. Quantitative findings revealed underreporting of acute gastroenteritis (AGE) and cholera in EWARS and an underutilization of the cholera RDTs, with only 2.6% of reported AGE cases screened using an RDT. This field evaluation demonstrated that RDTs can have an important role in cholera surveillance but highlighted significant challenges with cholera lab capacity, reporting, and training. Both the qualitative and quantitative findings showed gaps in surveillance reporting, which were exacerbated by the complexity of adding RDTs without strong guidance as well as beliefs about the RDTs' poor validity. These misconceptions and challenges need to be addressed at the local and national level to successfully scale-up cholera RDTs in Nepal and beyond.

Cholera diagnosis in human stool and detection in water: A systematic review and meta-analysis

BACKGROUND

Cholera continues to pose a problem for low-resource, fragile and humanitarian contexts. Evidence suggests that 2.86 million cholera cases and 95,000 deaths due to cholera are reported annually. Without quick and effective diagnosis and treatment, case-fatality may be 50%. In line with the priorities of the Global Task Force on Cholera Control, we undertook a systematic review and meta-analysis of diagnostic test accuracy and other test characteristics of current tests for cholera detection in stool and water.

METHODS

We searched 11 bibliographic and grey literature databases. Data was extracted on test sensitivity, specificity and other product information. Meta-analyses of sensitivity and specificity were conducted for tests reported in three or more studies. Where fewer studies reported a test, estimates were summarised through narrative synthesis. Risk of Bias was assessed using QUADAS-2.

RESULTS

Searches identified 6,637 records; 41 studies reporting on 28 tests were included. Twenty-two tests had both sensitivities and specificities reported above 95% by at least one study, but there was, overall, wide variation in reported diagnostic accuracy across studies. For the three tests where meta-analyses were possible the highest sensitivity meta-estimate was found in the Cholera Screen test (98.6%, CI: 94.7%-99.7%) and the highest specificity meta-estimate in the Crystal VC on enriched samples (98.3%, CI: 92.8%-99.6%). There was a general lack of evidence regarding field use of tests, but where presented this indicated trends for lower diagnostic accuracy in field settings, with lesser-trained staff, and without the additional process of sample enrichment. Where reported, mean test turnaround times ranged from over 50% to 130% longer than manufacturer's specification. Most studies had a low to unclear risk of bias.

CONCLUSIONS

Currently available Rapid Diagnostic Tests can potentially provide high diagnostic and detection capability for cholera. However, stronger evidence is required regarding the conditions required to secure these levels of accuracy in field use, particularly in low-resource settings.

REGISTRATION

PROSPERO (CRD42016048428).

Utility of Point of Care and Rapid Diagnostics in Humanitarian Emergencies

Background

In 2019, there were 70.8 million forcibly displaced people worldwide. Among the top causes of morbidity and mortality were measles, diarrhea, respiratory illness, and malaria. Availability of accurate diagnostics that are of low complexity, affordable, and produce timely results on site without the need for expensive laboratory equipment, extensive training, or distant transport of samples, are essential tools in the response to humanitarian emergencies (HE). Early detection of infectious diseases with epidemic potential and coordinated outbreak response, can result in significant decrease in morbidity and mortality.

Content

This review explores the utility of point of care and rapid diagnostic tests (POCT/RDTs) in HE and presents a review and analysis of the low complexity, availability, and ease of use of these diagnostic modalities that make them helpful tools in these settings, despite the generally lower test performance metrics associated with them over conventional laboratory-based assays. We review the literature to understand how POCT/RDTs have been used in HE response to produce lifesaving information without the need for a robust system for transporting test samples to more sophisticated laboratories, as this is often prohibitive in areas affected by conflict or natural disasters.

Summary

We propose that POCT/RDTs be considered essential healthcare tools provided to countries following a HE and suggest that UN agencies and vulnerable countries include effective RDTs in their essential diagnostics as part of their national preparedness and response plans.