These questions may be more difficult to answer than they seem. While some doctors are completely independent and others are full employees, other doctors may be affiliated with hospitals, without being employed by hospitals.
There are several approaches to measuring whether a physician is integrated within a hospital system:
- Basic measurement based on TIN. The standard approach to identifying whether a physician is embedded in a hospital is to examine whether that physician bills exclusively or primarily using a tax identification number (TIN) that belongs to a hospital or a health system that operates hospitals (also known as a “tin number”). related to the hospital. TIN”)–those that are considered integrated. This approach is useful but relies on a complete set of hospital TINs; Without a complete list, there are many false positives.
- Service location measurement. A second approach examines the frequency with which outpatient services are performed in hospital outpatient departments versus physician offices. Physicians who provide all or most of the outpatient services in an outpatient hospital are determined to be integrated. However, false positives may occur for non-integrated physicians using outpatient hospital facilities for selected procedures (e.g., surgeries); False negatives occur for integrated physicians who often provide outpatient services in a physician’s office.
- Membership-based approaches. These approaches rely on physician affiliation rather than a billing- or place-of-service-based approach to measuring integration. Common data sources used to identify affiliation include a proprietary IQVIA (formerly SK&A) database; and The Compendium of US Health Systems prepared by the Agency for Healthcare Research and Quality (AHRQ).
- “Advanced” TIN measurement. This approach was proposed in an article by Luo et al. (2024) and is similar to the basic TIN-based measure in that it is based on 3 steps: “(i) a multi-step search for hospital-related TINs using multiple sources for these TINs; (ii) use Medicare data to determine the TINs that physicians use to bill for services; and (iii) identify as integrated those physicians who primarily bill Medicare (75% or more) or exclusively use hospital-related TINs.” The authors also examine whether hospitals have a majority interest in medical TIN (based on IRS data), what they call the “network approach”; use AHA survey data to link hospitals and doctors (“indirect” approach).
Using these approaches, Luo and his co-authors find that the number of physicians embedded in hospitals increases over time. The “direct TIN match,” which is analogous to the basic TIN-based measure described above, shows that the proportion of doctors embedded in hospitals increased between 1999 and 2019. However, this figure peaks at just over 25%. If we incorporate the other methods of Luo et al. To measure the vertical integration of physicians, we not only found that the proportion of physicians integrated into hospital systems is much higher, but that the trend is much more pronounced. Specifically, the authors find that:
There was a steady increase in the percentage of integrated physicians from 19.5% of physicians in 1999 to 24.6% in 2005 and 43.5% in 2019.
You can read more details about this study. here. Below is a summary of the methods.
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