Why Do Physicians Vary So Widely in Their
Peter Franks, MD, Geoffrey C. Williams, MD, PhD, Jack Zwanziger, PhD,
Cathleen Mooney, MS, Melony Sorbero, MS
To determine which physician practice and psy-
chological factors contribute to observed variation in pri-
mary care physicians’ referral rates.
Cross-sectional questionnaire-based survey and anal-
ysis of claims database.
A large managed care organization in the Roches-
ter, NY, metropolitan area.
Internists and family physicians.
MEASUREMENTS AND MAIN RESULTS:
Patient referral status
(referred or not) was derived from the 1995 claims database
of the managed care organization. The claims data were also
used to generate a predicted risk of referral based on patient
age, gender, and case mix. A physician survey completed by a
sample of 182 of the physicians (66% of those eligible) in-
cluded items on their practice and validated psychological
scales on anxiety from uncertainty, risk aversiveness, fear of
malpractice, satisfaction with practice, autonomous and con-
trolled 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 exam-
ined using logistic regression. After adjustment for predicted
risk of referral (case mix), patients were more likely to be re-
ferred if their physician was female, had more years in prac-
tice, was an internist, and used a narrower range of diagnoses
(a higher Herfindahl index, also derived from the claims
data). Of the psychological 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
associated with referral likelihood.
Most of the explainable variation in referral
likelihood was accounted for by patient and physician prac-
tice factors like case mix, physician gender, years in prac-
tice, specialty, and the Herfindahl index. Relatively little
variation was explained by any of the examined physician
Primary health care; physician’s practice pat-
terns; referral and consultation.
J GEN INTERN MED 2000;15:163–168.
esearch from both the United Kingdom
has demonstrated that primary care
physicians exhibit wide variation in their referral rates. In
a previous report we found that case-mix-adjusted refer-
ral rates varied from less than 5% of patients referred per
year to more than 60%, and also that the referral rates
were stable over time and across diagnostic categories.
Thus, these variations reflect a relatively stable behavior
that is likely to have a significant impact on the access of
patients of primary care physicians to specialists. How-
ever, relatively little is known about the factors that drive
Patient characteristics, beyond the specific clinical
problem, affect the likelihood of being referred.
tion, physician and practice characteristics, such as spe-
and time pressure,
ported to affect referral rates. Taken together, however,
few of these factors have been found to account for much
of the observed variation in referral rates. In part, this
limitation reflects the small sample sizes involved in most
studies, so estimates of true referral rates are unstable,
and results have not been reproducible. More recently, at-
tention has focused on psychological factors that affect
this physician behavior.
Psychological factors, such
as risk aversion, tolerance of uncertainty, psychosocial
orientation, autonomous and controlled motivation for
test ordering, and patient centeredness, have been associ-
ated with physician behaviors and patient outcomes,
but very little of this research has examined the relation
to physician referral behavior.
To address this limitation, we examined the relation
between referral likelihood and physician factors, focus-
ing on practice and psychological factors. We obtained re-
ferral data from a large managed care organization (MCO)
to obtain stable estimates of the true contribution of phy-
sician factors to referral likelihood.
The database also
allowed adjustment for patient factors including age, sex,
and case mix.
The investigation was conducted in the Rochester, NY
metropolitan area using the claims database of the largest
local MCO. Approximately 500,000 persons (over 50% of
the local population) are enrolled in the MCO. The MCO
employs an independent practitioner association (IPA)
model, in which neither primary care physicians (PCPs)
nor specialists are capitated. No financial incentives are
Received from the Primary Care Institute, Department of Fam-
ily Medicine (PF), Departments of Medicine and Clinical and
Social Sciences in Psychology (GCW), and Department of Com-
munity and Preventive Medicine (JZ, CM, MS), University of
Rochester, Rochester, NY.
Address correspondence and reprint requests to Dr. Franks:
Dept. of Family Medicine, University of Rochester, 885 South
Ave., Rochester, NY 14620 (e-mail: peter_ franks@urmc.