Why do physicians vary so widely in their referral rates?

OBJECTIVE: To determine which physician practice and psychological factors contribute to observed variation in primary care physicians' referral rates . DESIGN: Cross-sectional questionnaire-based survey and analysis of claims d atabase. SETTING:A large managed care organization in the Rochester, NY, metropolita n area. PARTICIPANTS: Internists and family physicians. MEASUREMENTS AND MAIN RESULTS: Patient referral status (referred or not) wa s derived from the 1995 claims database of the managed care organization. T he claims data were also used to generate a predicted risk of referral base d on patient age, gender, and case mix. A physician survey completed by a s ample of 182 of the physicians (66% of those eligible) included items on th eir practice and validated psychological scales on anxiety from uncertainty , risk aversiveness, fear of malpractice, satisfaction with practice, auton omous and controlled motivation for referrals and test ordering, and psycho social beliefs. The relation between the risk of referral and the physician practice and psychological factors was examined using logistic regression. After adjustment for predicted risk of referral (case mix), patients were more likely to be referred if their physician was female, had more years in practice, was an internist, and used a narrower range of diagnoses (a high er Herfindahl index, also derived from the claims data). Of the psychologic al factors, only greater psychosocial orientation and malpractice fear was associated with greater likelihood of referral. When the physician practice factors were excluded from the analysis, risk aversion was positively asso ciated with referral likelihood. CONCLUSIONS: Most of the explainable variation In referral likelihood was a ccounted for by patient and physician practice factors like case mix, physi cian gender, years in practice, specialty, and the Herfindahl index. Relati vely Little variation was explained by any of the examined physician psycho logical factors.