Intended for healthcare professionals

CCBYNC Open access
Research Christmas 2012: Research

Using a dog’s superior olfactory sensitivity to identify Clostridium difficile in stools and patients: proof of principle study

BMJ 2012; 345 doi: (Published 13 December 2012) Cite this as: BMJ 2012;345:e7396
  1. Marije K Bomers, consultant1,
  2. Michiel A van Agtmael, consultant1,
  3. Hotsche Luik, canine trainer and psychologist2,
  4. Merk C van Veen, resident3,
  5. Christina M J E Vandenbroucke-Grauls, professor4,
  6. Yvo M Smulders, professor1
  1. 1Department of Internal Medicine, VU University Medical Centre, PO Box 7057, 1007 MB Amsterdam, Netherlands
  2. 2Scent Detection Academy and Research, Animal Behaviour and Cognition, HL&HONDEN, Edam, Netherlands
  3. 3Department of Internal Medicine, St Lucas Andreas Hospital, Amsterdam, Netherlands
  4. 4Department of Medical Microbiology and Infection Control, VU University Medical Centre
  1. Correspondence to: M K Bomers m.bomers{at}
  • Accepted 24 September 2012


Objective To investigate whether a dog’s superior olfactory sensitivity can be used to detect Clostridium difficile in stool samples and hospital patients.

Design Proof of principle study, using a case-control design.

Setting Two large Dutch teaching hospitals.

Participants A 2 year old beagle trained to identify the smell of C difficile and tested on 300 patients (30 with C difficile infection and 270 controls).

Intervention The dog was guided along the wards by its trainer, who was blinded to the participants’ infection status. Each detection round concerned 10 patients (one case and nine controls). The dog was trained to sit or lie down when C difficile was detected.

Main outcome measures Sensitivity and specificity for detection of C difficile in stool samples and in patients.

Results The dog’s sensitivity and specificity for identifying C difficile in stool samples were both 100% (95% confidence interval 91% to 100%). During the detection rounds, the dog correctly identified 25 of the 30 cases (sensitivity 83%, 65% to 94%) and 265 of the 270 controls (specificity 98%, 95% to 99%).

Conclusion A trained dog was able to detect C difficile with high estimated sensitivity and specificity, both in stool samples and in hospital patients infected with C difficile.


  • Contributors: MKB, MvA, CvdB-G, and YMS developed the concept and outlined the methods. HL trained the dog. MKB, HL, and MvV carried out the detection rounds and collected the data. MKB analysed the data and drafted the paper. MvA, CvdB-G, and YMS provided conceptual and technical guidance. All authors critically appraised the paper, revised where appropriate and approved the final version of the manuscript. MKB and YMS are the guarantors.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: HL is the owner and chairman of the Animal Behaviour and Cognition, Scent Detection Research and Academy HL&HONDEN, Edam, Netherlands; otherwise no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The research protocol was approved by the institutional review boards of both hospitals.

  • Data sharing: No additional data available.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

View Full Text