Questionnaire validation: Retrospective analysis of clinical data

Clinical Nutrition published our trial “Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals” [ [1] ]. The main outcomes were that supplementation with Bifidobacterium animalis subp. lactis Bl-04™ and the combination of Lactobacillus acidophilus NCFM® and B. animalis subsp. lactis Bi-07™ (NCFM & Bi-07) for 150 days in healthy adults was associated with beneficial effects for upper respiratory tract illness (URTI). A key criticism of community-based studies such as ours is whether self-reported data reflects the diagnosis that would be made of the illness by a trained specialist –so-called physician verification. This concern is also reflected by regulatory bodies whom note that outcomes should be measured by generally accepted methods including validated questionnaire-based assessments [ [2] ].