Evaluation of Crystal® VC Rapid Diagnostic Test kit to detect Vibrio cholerae from fecal samples in Ethiopia

Abstract

Background: The Crystal® VC Rapid Diagnostic Test (RDT) has been shown to be a sensitive, rapid, cost-effective, and time-efficient tool for detecting V. cholerae. Although this test has advantages in terms of sensitivity and specificity, there are no reports on how well it performs across different regions and during various seasons in Ethiopia to assess its robustness.

Objective: The study aimed to evaluate the diagnostic performance of Crystal^® VC RDT rapid Diagnostic Test to detect V. cholerae from fecal samples in Ethiopia.

Method: A cross-sectional study was conducted from October 2022 to February 2024 at cholera outbreak sites across Ethiopia.  A total of 361 fecal samples were collected and tested concurrently using Crystal® VC RDT and standard culture methods. Sensitivity, specificity and positive and negative predictive value of the Crystal® VC RDT were calculated using culture as the gold standard. Agreement between the two diagnostic methods was assessed using Cohen’s Kappa statistic.  Data analysis was performed using SPSS version 25 and MedCalc computer software.

Results: Of the 361 fecal samples analyzed, 123 (34%) were confirmed positive for Vibrio cholerae by culture. The Crystal® VC RDT demonstrated a sensitivity of 98.4% (95% CI: 94.3% –99.8%) and a specificity of 52.1% (95% CI: 45.6%–58.6%).The PPV was 51.5% (95% CI: 48.1%–54.8%) and the NPV was 98.4% (95% CI: 94.0%–99.6%). The test showed a moderate agreement with culture (kappa =0.679).

Conclusion: Crystal® VC RDT demonstrate high sensitivity and excellent NPV, making it a valuable tool for early detection and rapid response during cholera outbreaks. Despite lower specificity, the test’s speed and ease use support its utility in field settings and epidemiological surveillance in resource-limited areas.