Evaluation of three rapid diagnostic tests for cholera: does the skill level of the technician matter?

OBJECTIVE To evaluate SMART(TM), Medicos(TM) Dip Stick and an Institut Pasteur (IP) cholera dipstick tests for accuracy and ease of use. METHOD Every 50th patient presenting with diarrhoea at ICDDR,B between 1 April 2003 and 30 November 2003 was enrolled. The rapid diagnostic tests were performed by field and laboratory technicians, and sensitivity (Se), specificity (Sp), positive (PPV) and negative (NPV) predictive values calculated. RESULTS We isolated Vibrio cholerae O1 from 116 (38%) of 304 patients. The Se, Sp, PPV and NPV of the SMART(TM) test were 58%, 95%, 84% and 84% for field technicians, and 83%, 88%, 83% and 88% for laboratory technicians. The Se, Sp, PPV and NPV of the IP dipstick test were 93%, 67%, 63% and 94% for field technicians, and 94%, 76%, 70% and 95% for laboratory technicians. The Se, Sp, PPV and NPV of the Medicos(TM) test were 84%, 79%, 71% and 90% for field technicians, and 88%, 80%, 72% and 92% for laboratory technicians. A high proportion of indeterminates (30%) hampered the performance of the SMART(TM) test. The IP dipstick had the highest Se, irrespective of technician skill level. CONCLUSIONS The IP dipstick is the most appropriate rapid diagnostic assay for the detection of V. cholerae O1 in locations where the skill level of personnel may be low, such as remote areas or refugee camp settings. High cost may limit the utility of any diagnostic test in the developing world.