Accuracy of giant African pouched rats for diagnosing tuberculosis: comparison with culture and Xpert ® MTB/RIF

Int J Tuberc Lung Dis. 2017 Nov 1;21(11):1127-1133. doi: 10.5588/ijtld.17.0139.

Abstract

Setting: Enhanced tuberculosis (TB) case finding using detection rats in Tanzania.

Objectives: To assess the diagnostic accuracy of detection rats compared with culture and Xpert® MTB/RIF, and to compare enhanced case-finding algorithms using rats in smear-negative presumptive TB patients.

Design: A fully paired diagnostic accuracy study in which sputum of new adult presumptive TB patients in Tanzania was tested using smear microscopy, 11 detection rats, culture and Xpert.

Results: Of 771 eligible participants, 345 (45%) were culture-positive for Mycobacterium tuberculosis, and 264 (34%) were human immunodeficiency virus (HIV) positive. The sensitivity of the detection rats was up to 75.1% (95%CI 70.1-79.5) when compared with culture, and up to 81.8% (95%CI 76.0-86.5) when compared with Xpert, which was statistically significantly higher than the sensitivity of smear microscopy. Corresponding specificity was 40.6% (95%CI 35.9-45.5) compared with culture. The accuracy of rat detection was independent of HIV status. Using rats for triage, followed by Xpert, would result in a statistically higher yield than rats followed by light-emitting diode fluorescence microscopy, whereas the number of false-positives would be significantly lower than when using Xpert alone.

Conclusion: 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Animals
  • Bacteriological Techniques
  • False Positive Reactions
  • Female
  • Humans
  • Male
  • Microscopy
  • Microscopy, Fluorescence
  • Middle Aged
  • Mycobacterium tuberculosis / isolation & purification*
  • Rats
  • Sensitivity and Specificity
  • Smell / physiology*
  • Sputum / microbiology*
  • Tanzania
  • Tuberculosis / diagnosis*