Abstract:
SETTING: Resource-limited settings in sub-Saharan African
countries.
OBJECTIVE: To utilise African giant pouched rats (Cricetomys
gambianus) for the diagnosis of tuberculosis
(TB) in human sputum.
DESIGN: A specially designed cage with 10 sniffi ng holes
and cassette-carrier was used. The sputum samples were
put in the sample cassette, containing 10 samples in line,
placed under matching sniffi ng holes. Rats were trained
to sniff each consecutive sample, and indicate TB positives
by fi xing their nose for 5 seconds at the sniffi ng hole. This
behaviour was maintained by food reinforcement upon
correct indications. A total of 3416 samples were used.
RESULTS: Of the 20 trained rats, 18 were able to discriminate
positive from negative sputum samples, with
average daily sensitivities ranging from 72% to 100%,
and average daily false-positives ranging from 0.7% to
8.1%. The use of multiple rats signifi cantly increased
sensitivity and negative predictive value.
CONCLUSION: Utilising trained sniffer rats for TB detection
is a potentially faster screening method and is at
least as sensitive as smear microscopy. This method could
therefore be suitable for active case fi nding, especially
where large numbers of samples are to be analysed in
resource-limited settings, to complement existing diagnostic
techniques.
