Mapping physician networks with self-reported and administrative data

Abstract

Objective: To assess whether connections between physicians based on shared patients in administrative data correspond with professional relationships between physicians.

Data sources/study setting: Survey of physicians affiliated with a large academic and community physicians' organization and 2006 Medicare data from a 100 percent sample of patients in the Boston Hospital referral region.

Study design/data collection: We administered a web-based survey to 616 physicians (response rate: 63 percent) about referral and advice relationships with physician colleagues. Relationships measured by this questionnaire were compared with relationships assessed by patient sharing, measured using 2006 Medicare data. Each physician was presented with an individualized roster of physicians' names with whom they did and did not share patients based on the Medicare data.

Principal findings: The probability of two physicians having a recognized professional relationship increased with the number of Medicare patients shared, with up to 82 percent of relationships recognized with nine shared patients, overall representing a diagnostic test with an area under the receiver-operating characteristic curve of 0.73 (95 percent CI: 0.70-0.75). Primary care physicians were more likely to recognize relationships than medical or surgical specialists (p<.001).

Conclusions: Patient sharing identified using administrative data is an informative "diagnostic test" for predicting the existence of relationships between physicians. This finding validates a method that can be used for future research to map networks of physicians.

Figure 1

Probability That Respondents Identified a Relationship to a Listed Physician by Number of Patients Shared This figure shows the proportion of ties to physicians that respondents identified as true relationships based on the number of Medicare patients shared in 2006. The x-axis represents the number of patients shared for a group of ties in the Medicare data and the y-axis shows the proportion of all ties of the strength on the x-axis that were identified by respondents as either having any connection (A), any referral relationship (B), or any advice relationship (C). Because of small sample sizes of ties above 10 patients shared, all ties with a value of 10 or more patients shared are included in the “10+” level on the x-axis.

Figure 2

Receiver Operating Characteristic Curve for Existence of Any Relationship between Physicians ROC curve (dotted line) for identifying any relationship between two physicians based on the number of shared Medicare patients in 2006. Number labels show the point on the ROC curve corresponding to each possible cutoff of Medicare patients shared during 2006 up to 10 or more patients shared. The solid line shows a line of slope 1 (or the ROC curve for a diagnostic test no better than chance) as a guide. The area under the curve of this ROC curve (or c statistic) is 0.73, 95 percent confidence interval: 0.70–0.75.

Figure 3

Physician Networks Constructed from Survey-Based and Claims-Based Relationships This figure depicts two different plots of the largest connected network of physicians in the survey sample and their relationships. For visual clarity, only ties with a strength of six patients shared or higher are shown in both (A) and (B), which excludes some of the physicians and relationships. (A) depicts the relationships among the sampled physician population (including nonrespondents) as measured by the relationships presented in the survey (no more than 20 per respondent), with ties recognized in the survey labeled as blue lines and ties measured by Medicare claims, but not recognized by a respondent shown in gray. (B) shows the same set of respondents and nonrespondents, with the addition that all ties and other physician relationships measured by administrative claims are displayed, with the ties confirmed by survey measurement (by design a small subset of total sample of ties) highlighted in blue.