Blinding terminology used in reports of randomized controlled trials involving dogs and cats

To review blinding terminology used in published reports of veterinary clinical randomized controlled trials (RCTs) and to determine how practicing veterinarians interpret blinding terminology.

Retrospective literature review and prospective veterinarian survey.

195 parallel-group clinical RCTs published from June 2004 to June 2010 in 11 peer-reviewed journals; 21 practicing veterinarians at a university-based small animal teaching hospital.

Journals were hand searched to identify eligible reports. Details concerning trial methodology were recorded. Veterinarians provided information regarding position, experience, and personal interpretation of blinding terminology via an anonymous questionnaire.

Blinding was reported or inferred in 131 reports of RCTs, yet complete descriptions of who was blinded were present in only 42 (32.1%) reports. Studies for which blinding was reported with the terms single or double blinded were less likely to contain clear descriptions of the role of blinded study personnel, compared with studies reported as blinded or in which blinding was inferred through trial methodology. Veterinarians did not agree on how to interpret the terms single, double, and triple blinded when reading the report of an RCT.

Blinding was commonly used as a means of reducing bias associated with collection and interpretation of data in reports of veterinary RCTs. However, most reports of blinding methodology were incomplete and there was no consistency in how blinding terminology was used by authors or interpreted by veterinarians. Ambiguous reporting hinders the ability of practitioners to assess the validity of trial results and make informed decisions about applying study findings to their patient populations.