- Carolyn M Willis, senior research scientist ()1,
- Susannah M Church, honorary research fellow1,
- Claire M Guest, operations director2,
- W Andrew Cook, deputy chief executive2,
- Noel McCarthy, medical statistician3,
- Anthea J Bransbury, associate specialist1,
- Martin R T Church, honorary research fellow1,
- John C T Church, honorary consultant1
- 1 Department of Dermatology, Amersham Hospital, Amersham HP7 0JD
- 2 Hearing Dogs for Deaf People, Saunderton, Princes Risborough HP27 9NS
- 3 Centre for Statistics in Medicine, Institute of Health Sciences, Oxford OX3 7LF
- Correspondence to: C M Willis
- Accepted 19 July 2004
Objective To determine whether dogs can be trained to identify people with bladder cancer on the basis of urine odour more successfully than would be expected by chance alone.
Design Experimental, “proof of principle” study in which six dogs were trained to discriminate between urine from patients with bladder cancer and urine from diseased and healthy controls and then evaluated in tests requiring the selection of one bladder cancer urine sample from six controls.
Participants 36 male and female patients (age range 48-90 years) presenting with new or recurrent transitional cell carcinoma of the bladder (27 samples used for training; 9 used for formal testing); 108 male and female controls (diseased and healthy, age range 18-85 years—54 samples used in training; 54 used for testing).
Main outcome measure Mean proportion of successes per dog achieved during evaluation, compared with an expected value of 1 in 7 (14%).
Results Taken as a group, the dogs correctly selected urine from patients with bladder cancer on 22 out of 54 occasions. This gave a mean success rate of 41% (95% confidence intervals 23% to 58% under assumptions of normality, 26% to 52% using bootstrap methods), compared with 14% expected by chance alone. Multivariate analysis suggested that the dogs' capacity to recognise a characteristic bladder cancer odour was independent of other chemical aspects of the urine detectable by urinalysis.
Conclusions Dogs can be trained to distinguish patients with bladder cancer on the basis of urine odour more successfully than would be expected by chance alone. This suggests that tumour related volatile compounds are present in urine, imparting a characteristic odour signature distinct from those associated with secondary effects of the tumour, such as bleeding, inflammation, and infection.
Contributors All authors participated in conception and design of the study, interpretation of data, and critical revision of the manuscript. SMC, JCTC, MRTC, and CMW did the patient recruitment and sample collection, and CMW was also responsible for the storage and management of the urine samples. WAC and CMG had overall responsibility for the training of the dogs. With the exception of NMcC and AJB, all authors contributed to the acquisition of data. NMcC did the statistical analysis. CMW drafted the manuscript, with assistance from SMC and NMcC. CMW is the guarantor and accepts full responsibility for the conduct of the study, had access to the data, and controlled the decision to publish.
Funding The Department of Dermatology, Amersham Hospital, received financial support from the Erasmus Wilson Dermatological Research Fund (registered charity No 313305), which had no active role in the design or conduct of the study. The dog trainers, all employees of Hearing Dogs for Deaf People (registered charity No 293358), trained the dogs in their own time; their expenses were met through a private donation given by Derek Wilton, who did not participate in the study in any way. SMC, MRTC, and JCTC were funded by their small family company COBiRD Ltd (company No 03426189), which also contributed to the project expenses.
Competing interests None declared.
Ethical approval South Buckinghamshire local research ethics committee approved the study.