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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 database.
SETTING: A large managed care organization in the Rochester, NY, metropolitan area.
PARTICIPANTS: 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) included items on their practice and validated psychological scales on anxiety from uncertainty, risk aversiveness, fear of malpractice, satisfaction with practice, autonomous 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 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.
CONCLUSIONS: Most of the explainable variation in referral likelihood was accounted for by patient and physician practice factors like case mix, physician gender, years in practice, specialty, and the Herfindahl index. Relatively little variation was explained by any of the examined physician psychological factors.
Research from both the United Kingdom 1 and the United States 2 has demonstrated that primary care physicians exhibit wide variation in their referral rates. In a previous report we found that case-mix-adjusted referral 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. 3 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. However, relatively little is known about the factors that drive these differences. 4
Patient characteristics, beyond the specific clinical problem, affect the likelihood of being referred. 5–7 In addition, physician and practice characteristics, such as specialty, 8,9 reimbursement, 10 and time pressure, 2 are reported 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, 11 and results have not been reproducible. More recently, attention has focused on psychological factors that affect this physician behavior. 12,13 Psychological factors, such as risk aversion, tolerance of uncertainty, psychosocial orientation, autonomous and controlled motivation for test ordering, and patient centeredness, have been associated with physician behaviors and patient outcomes, 14–21 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, focusing on practice and psychological factors. We obtained referral data from a large managed care organization (MCO) to obtain stable estimates of the true contribution of physician factors to referral likelihood. 11 The database also allowed adjustment for patient factors including age, sex, and case mix.
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Table 1 shows, at the physician level, the distributions of the main variables of interest. About 40% of patients were referred each year, and case-mix adjustment produced relatively little change on the range of referral rates (2%–65%). Both the observed and case-mix-adjusted referral rates exhibited moderate correlations with a number of the physician practice variables (older physicians, internists, solo practitioners, physicians practicing longer, and longer in their current practice, those with more sessions per week, and physicians with higher Herfindahl indices all referred more). Of the psychological variables, only risk aversion was associated with a higher referral rate.
Table 1. Distributions of Main Variables of Interest *
|Observed referral rate||0.38||0.12||0.01||0.69|
|Adjusted referral rate||0.40||0.10||0.02||0.65|
|Percent female physicians||19|| || || |
|Percent family physicians||34|| || || |
|Percent solo practice||28|| || || |
|Number of partners||3.38||7.16||0.00||70.00|
|Years in practice||15.74||8.76||3.00||43.00|
|Years in current practice||12.87||8.76||1.00||43.00|
|Sessions per week||7.77||1.72||1.00||11.00|
|Patients per week||101.00||34.38||32.00||250.00|
|Malpractice fear (1–5)||3.31||0.84||1.33||5.00|
|Autonomous motivation (1–7)||6.03||0.89||2.75||7.00|
|Controlled motivation (1–7)||2.87||1.08||1.00||6.00|
|Anxiety from uncertainty (1–6)||3.40||1.17||1.00||5.67|
|Psychosocial beliefs (1–5)||4.22||0.55||1.33||5.00|
|Risk seeking (1–5)||3.03||0.94||1.00||6.00|
|Physician satisfaction (1–5)||3.59||0.48||2.38||4.81|
The results of the GEE logistic regression analyses are shown in Tables 2 and 3. After adjustment, the only physician practice variables that were associated with a greater probability of referral were being a female physician, being in practice longer, being an internist, and having a higher Herfindahl index (using a narrower range of diagnoses). In contrast to the moderate effects associated with the physician practice variables, of the psychological variables, only psychosocial orientation exhibited any statistically significant association (P = .04); patients of more psychosocially oriented physicians were more likely to be referred. The associations with malpractice fear was borderline significant (P = .08); there was a trend for patients of physicians with higher levels of malpractice fear to be more likely to be referred. Excluding the nonsignificant psychological variables had little impact on the parameter estimates or confidence intervals of the remaining variables. The analyses excluding the physician practice variables were similar (Table 3), except that risk aversiveness was the most important psychological variable; patients of risk averse physicians were more likely to be referred (P = .005).
Table 2. Adjusted Relations Between Referral of Patients and Physician Practice and Psychological Risk Factors *
|Risk Factor||Odds Ratio (95% Confidence Interval)|
| ||Practice Factors Only||Practice and All Psychological Factors ||Practice and Statistically Significant Psychological Factors |
|Predicted referral probability||4.51 (4.29 to 4.75)||4.50 (4.28 to 4.73)||4.53 (4.31 to 4.75)|
|Female physician||1.17 (1.05 to 1.31)||1.26 (1.12 to 1.41)||1.21 (1.08 to 1.36)|
|Family physician||0.70 (0.62 to 0.80)||0.72 (0.64 to 0.81)||0.72 (0.63 to 0.81)|
|Years in practice||1.06 (1.00 to 1.11)||1.09 (1.03 to 1.15)||1.07 (1.01 to 1.12)|
|Herfindahl index||1.09 (1.02 to 1.16)||1.11 (1.04 to 1.18)||1.14 (1.07 to 1.20)|
|Autonomous motivation|| ||0.99 (0.93 to 1.06)|| |
|Controlled motivation|| ||0.99 (0.94 to 1.05)|| |
|Risk seeking|| ||0.96 (0.91 to 1.01)|| |
|Anxiety from uncertainty|| ||0.98 (0.93 to 1.04)|| |
|Physician satisfaction|| ||0.95 (0.90 to 1.01)|| |
|Psychosocial orientation|| ||1.06 (1.00 to 1.14)||1.05 (1.00 to 1.12)|
|Malpractice fear|| ||1.05 (0.99 to 1.11)||1.06 (1.01 to 1.12)|
Table 3. Adjusted Relations Between Referral of Patients and Physician Psychological Factors *
|Risk Factor||Odds Ratio (95% confidence Interval)|
| ||All Psychological Factors ||Statistically Significant Psychological Factors |
|Predicted referral probability||4.45 (4.22 to 4.69)||4.45 (4.23 to 4.69)|
|Autonomous motivation||1.02 (0.96 to 1.08)|| |
|Controlled motivation||0.97 (0.92 to 1.03)|| |
|Risk seeking||0.93 (0.89 to 0.98)||0.93 (0.89 to 0.98)|
|Anxiety from uncertainty||1.04 (0.98 to 1.10)|| |
|Physician satisfaction||1.03 (0.97 to 1.09)|| |
|Psychosocial orientation||1.05 (0.98 to 1.12)||1.05 (1.00 to 1.11)|
|Malpractice fear||1.04 (0.99 to 1.10)|| |
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Our previous results suggested that physician referral rates represent a physician behavior that is stable across time and diagnostic categories. 3 This study suggests that most of the physician contribution to referral likelihood is related to physician practice factors like physician gender, years of practice, specialty, and Herfindahl index. The psychological measures examined in this study explained relatively little of the variability in referral likelihood. In the models that included the physician practice factors, only 2 of the psychological variables exhibited effects with borderline statistical significance. The odds ratios for the effects of the psychological factors were all close to 1, and the confidence intervals were narrow (Table 2), suggesting it is unlikely that any important effects were missed. In the models that excluded the physician practice factors, risk aversion exhibited a moderate effect, suggesting its effects are mediated by physician practice factors. Other analyses suggest that this effect reflects stylistic differences between family physicians and internists. 35
The relations between referral likelihood and case mix, physician gender, and specialty are consistent with prior research. 1,2,36 The greater referral likelihood of patients with more specialized physicians (higher Herfindahl index) is consistent with prior research suggesting that physicians with more expertise in an area may refer patients more often than other physicians. 26,27
Studies have demonstrated effects of physician psychological factors, including those measured in this study, on patient outcomes, particularly costs and satisfaction. 14–21 In analyses not reported here, we found associations between some of the measured psychological factors and some other variables in the claims database, such as costs generated and coding of mental health diagnoses. Thus, it is unlikely that the limited associations observed between psychological factors and referral likelihood reflect simply a measurement problem. There was, however, some evidence of a “ceiling” phenomenon for the autonomous motivation and psychosocial beliefs scales; physicians had, on average, very high scores, with little room for variance above the average.
It remains possible that the psychological factors would exhibit a stronger relation with more specific kinds of referrals, an effect that is lost in the general tendency to make referrals. However, getting reliable estimates of referral likelihoods for specific kinds of referrals would require a much larger database than even the one used in this study. 11 Referrals for specific conditions are relatively rare, 26 and linking a sufficiently large database to physician-identified reasons for referral is likely to be difficult. It is also possible that other domains of the measured psychological constructs, especially reactions to anxiety 30 and self-determination theory, 20 explain some of the unexplained referral variability. The results obtained apply to those physicians enrolled in the study. Although the physicians in the study were similar in some respects to other local physicians, the extent to which these findings generalize to other primary care physicians is unknown. Finally, it is also possible that unmeasured patient characteristics such as patient preferences, socioeconomic status, or prior relationship with a specialist affect referral likelihood. We conclude, however, that currently available psychological measures do not provide robust explanations for a critical physician behavior, one that has significant implications for patients' access to specialty care.