%0 Journal Article %A Frederick M. Chen %A George E. Fryer, Jr. %A Thomas E. Norris %T Effects of Comorbidity and Clustering upon Referrals in Primary Care %D 2005 %R 10.3122/jabfm.18.6.449 %J The Journal of the American Board of Family Practice %P 449-452 %V 18 %N 6 %X Objective: To examine the effect of patient characteristics and comorbidity on referrals in primary care.Methods: Cross-sectional analysis of patient encounters and referrals during a 1-year period for a primary care network of 9 clinics. The analysis adjusted for the clustering effect of physicians and clinics on the data.Results: 23,720 specialty referrals were generated from 251,240 patient encounters, resulting in a total referral rate of 9.4 referrals per 100 encounters. Age, gender, and certain comorbid conditions were significant predictors of referral for any given encounter.Conclusions: Patient characteristics and comorbidity are predictors of referral. Studies of primary care processes need to account for clustering of physicians and clinics in their research design. %U https://www.jabfm.org/content/jabfp/18/6/449.full.pdf