Number needed to benefit from information (NNBI): proposal from a mixed methods research study with practicing family physicians.

PURPOSE: We wanted to describe family physicians' use of information from an electronic knowledge resource for answering clinical questions, and their perception of subsequent patient health outcomes; and to estimate the number needed to benefit from information (NNBI), defined as the number of patients for whom clinical information was retrieved for 1 to benefit.
METHODS: We undertook a mixed methods research study, combining quantitative longitudinal and qualitative research studies. Participants were 41 family physicians from primary care clinics across Canada. Physicians were given access to 1 electronic knowledge resource on handheld computer in 2008-2009. For the outcome assessment, participants rated their searches using a validated method. Rated searches were examined during interviews guided by log reports that included ratings. Cases were defined as clearly described searches where clinical information was used for a specific patient. For each case, interviewees described information-related patient health outcomes. For the mixed methods data analysis, quantitative and qualitative data were merged into clinical vignettes (each vignette describing a case). We then estimated the NNBI.
RESULTS: In 715 of 1,193 searches for information conducted during an average of 86 days, the search objective was directly linked to a patient. Of those searches, 188 were considered to be cases. In 53 cases, participants associated the use of information with at least 1 patient health benefit. This finding suggested an NNBI of 14 (715/53).
CONCLUSION: The NNBI may be used in further experimental research to compare electronic knowledge resources. A low NNBI can encourage clinicians to search for information more frequently. If all searches had benefits, the NNBI would be 1. In addition to patient benefits, learning and knowledge reinforcement outcomes are frequently reported.