Table 2.

Participants with a discrepancy between laboratory results and dog response

Variables	Dog response	Laboratory tests*	Diarrhoea on day of detection round	Comment
Inconclusive dog response:
Case 1	Inconclusive	Positive result	Yes	Dog appeared distracted by plastic cup on floor
Control 2	Inconclusive	Negative result	Yes	During this round there was a strong chlorine smell in several rooms, from disinfection, which could have influenced the dog’s response. Tests were done on participants with an inconclusive response in this round
Case 3	Inconclusive	Positive result	Yes	Chlorine round, see comment for control 2
Control 4	Inconclusive	Not done	No	Case 5 had just changed beds; the dog seemed to have difficulty choosing between two neighbouring patients (control 4 and case 5) and the third (empty) bed across the room; he sat in the middle
Case 5	Inconclusive	Positive result	Yes	See comment for control 4
Control 6	Inconclusive	Negative result	Yes	On the ward was a patient with Clostridium difficile infection who refused to participate in the study. The dog was not allowed to enter the patient’s room; however, the dog was excited and tried to enter. When forced to move away, he immediately sat down next to control 6, who was the first participant he encountered. Because of symptoms, tests had been done. The enzyme immunoassay gave a negative result; however, stool culture showed non-toxigenic C difficile
Control 7	Inconclusive	Negative result	Yes	No apparent explanation
False positives†:
Control 8	Positive	Negative result	No	Chlorine round, see comment for control 2. Enzyme immunoassay gave a negative result; however, stool culture showed non-toxigenic C difficile
Control 9	Positive	Not done	No	Participant offered the dog a cookie
Control 10	Positive	Not done	No	Participant beckoned the dog
Control 11	Positive	Negative result	No	Dog appeared distracted by urine on the floor from a broken catheter bag
Control 12	Positive	Negative result	No	This participant had been treated for C difficile infection, diagnosed 11 days previously. Since symptoms resolved on the day of the detection round, the patient was included as a control. However, a week after the round symptoms returned and retesting showed a relapse
False negatives‡:
Case 13	Negative	Positive result	Yes	No clear explanation
Case 14	Negative	Positive result	Yes	The enzyme immunoassay gave a positive result; culture was mistakenly not done

*Enzyme immunoassay+toxigenic culture.

†Participants with negative laboratory results but positive dog response.

‡Participants with negative laboratory results but positive dog response.