BackgroundAfrican pouched rats sniffing sputum samples provided by local clinics have significantly increased tuberculosis case findings in Tanzania and Mozambique. The objective of this study was to determine the reproducibility of rat results.MethodsOver an 18-month period 11,869 samples were examined by the rats. Intra-rater reliability was assessed through Yule’s Q. Inter-rater reliability was assessed with Krippendorff’s alpha.ResultsIntra-rater reliability was high, with a mean Yule’s Q of 0.9. Inter-rater agreement was fair, with Krippendorf’s alpha ranging from 0.15 to 0.45. Both Intra- and Inter-rater reliability was independent of the sex of the animals, but they were positively correlated with age. Both intra- and inter-rater agreement was lowest for samples designated as smear-negative by the clinics.ConclusionOverall, the reproducibility of tuberculosis detection rat results was fair and diagnostic results were therefore independent of the rats used.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2347-3) contains supplementary material, which is available to authorized users.

Although detection rats did not meet the accuracy criteria as standalone diagnostic or triage testing for presumptive TB, they have additive value as a triage test for enhanced case finding among smear-negative TB patients if more advanced diagnostics are not available.

No abstract

In this study, we trialed the use of a semiautomated line cage with African pouched rats for scent-detection tasks. The apparatus was a 2100 ϫ 410 ϫ 520-mm cage with 10 wells in the floor, under which samples were loaded. A nose-poke response was recorded by an infrared beam. Breaking this beam for a predetermined duration over a target sample triggered automatic delivery of a food pellet. We used a library of scents commonly used in the fragrance industry as stimuli. Ten rats were trained to discriminate a target from 9 other scents, and demonstrated a mean sensitivity of 94.23% and specificity of 95.1% at the conclusion of training. The value of measuring subthreshold responses and the importance of conducting research with controlled samples is discussed, as is the potential application of this technology to other scent-detection problems.