Evidence based general practice.

Objectives: to estimate the proportion of interventions in general practice that are based on evidence. Design: a one-year cross-sectional study involving all consultations by patients over age 15 years seen in 34 national primary health care centers. Setting: the rural Castellon provincial district within the Valencian Community in eastern Spain, with a total population of 21,155 inhabitants. Subjects: of 1990 case histories registered in the course of one year, 4800 consultations were identified; of these, 2341 (49%) distinct diagnosis–intervention pairs were identified and coded. Main results: the evidence basis for the diagnosis–intervention pairs in the study was derived from a computerized search of the scientific literature published in 1992–1996. The quality of the evidence was classified according to the method of Ellis et al. Within the 2341 diagnosis–intervention pairs, there was positive evidence in support of the intervention used in 55%. The evidence basis was sound for 42%, with 38% being based on Type I (clinical trials) evidence and 4% on Type II evidence. The most frequently presenting diseases involved the circulatory (18.7%), respiratory (14.9%), nervous (14.2%), musculo-skeletal (12.5%) and nutrition and metabolism and digestive systems, with 12.1% each. Conclusions: clinical practice was clearly supported by positive evidence of all Types (I–III) in a total of 55% of interventions, and by good positive evidence of Type I or II in 42% of interventions. The percentage of evidence-based interventions in general practice serving a substantial population in rural Spain was lower than had been reported by some authors.