Quantifying the primary care workforce in the U.S.: A validation study with and without an imperfectly measured...

To validate the National Provider Identifier (NPI), a commonly used data source in health services research, for identifying primary care physicians, physician assistants (PAs), and nurse practitioners (NPs).

Validation studies to calculate the sensitivity, specificity, and associated 95 % confidence intervals for physicians, PAs, and NPs. For physicians, Medicare claims data were used as an imperfectly measured referent standard. For PAs and NPs, we used a simulation-based method to estimate accuracy parameters that assumed the NPI and Medicare claims were equally misclassified.

Using the Medicare claims as the referent standard for physicians yielded a sensitivity and specificity of 0.95 (95 % CI: 0.88, 0.98) and 0.76 (95 % CI: 0.73, 0.79), respectively. Using the simulation-based method yielded a sensitivity and specificity of 0.57 (95 % CrI: 0.11, 0.97) and 0.56 (95 % CrI: 0.10, 0.96), respectively for PAs and 0.58 (95 % CrI: 0.13, 0.97) and 0.61 (95 % CrI: 0.14, 0.97), respectively for NPs.

Our validation results varied by provider role. Accuracy was highest for physicians further highlighting the challenges in quantifying PAs and NPs based on their NPI alone. Failure to consider potential misclassification in the NPI may result in biased research findings.