services (including emergency care and admitting & screening); and long-term care—nursing home and intermediate care.
A PF is estimated statistically for each PCA. To derive the total physician FTEE in a given specialty (e.g., neurology) or program area (e.g., ambulatory care) required for patient care at a given VAMC, one must solve for the FTEE required to meet patient workload on each relevant PCA, then sum across PCAs.
In the inverse production function (IPF) variant of the EBPSM, specialty-specific rather than PCA-specific models are estimated. For a given specialty (e.g., neurology), the quantity of physician FTEE devoted to patient care and resident education across all PCAs at the VAMC is hypothesized to be a function of such factors as total inpatient workload associated with that specialty (e.g., total bed-days of care for patients assigned a neurology-associated diagnosis-related group); total ambulatory care workload associated with the specialty; total long-term care workload associated with the specialty; the number of residents in that specialty at the VAMC, by postgraduate year; and other variables possibly associated with physician time devoted to patient care and resident education.
There are separate facility-level IPFs for each of the following 11 specialty groups: medicine, surgery, psychiatry, neurology, rehabilitation medicine, anesthesiology, laboratory medicine, diagnostic radiology, nuclear medicine, radiation oncology, and spinal cord injury. (Included in this latter group are physicians in any specialty who are assigned to the spinal cord injury "cost center" in the VA personnel data system.)
For each specialty, to derive the total number of physicians required for patient care and resident education on the PCAs, one must substitute the appropriate values of workload, resident FTEE, and other control variables into that specialty's IPF, then solve directly for the corresponding physician FTEE level. The statistical confidence limits on the prediction also can be computed directly (which is not possible for the PF-based FTEE estimate, as will be seen).
Both the PF and the IPF deal with only a portion of total physician FTEE at the VAMC, albeit a very important and quantitatively significant portion in each case. The fraction of physician FTEE allocated to patient care only—the focus of the PF variant—will vary by specialty and facility, of course, but it rarely falls below 65 percent and generally lies in the 70-95 percent range (see Table 9.1 in chapter 9). The sum of FTEE devoted to patient care and resident education—the focus of the IPF variant—generally lies in the 80-95 percent range. (The rationale for including both patient care and resident education in the IPF and only patient care in the PF is discussed in the section on Formal Presentation of the EBPSM.)
It follows that, under either the PF or IPF variant, total FTEE required at the facility is the sum of the model-derived estimate plus separate estimates for FTEE components not incorporated in the model. Included in the latter would be FTEE for research, continuing education, and other miscellaneous assignments. The process of deriving total physician FTEE for a given specialty