Billing for physician services: a comparison of actual billing with CPT codes assigned by direct observation.

BACKGROUND: Little is known about the accuracy of family physicians' use of the Current procedural Terminology (CPT) coding scheme for office visits, despite increased administrative oversight of Medicare billing practices. In addition, the patient and visit characteristics that are associated with over- and undercoding are not well understood. METHODS: This study compared coding for evaluation and management (E&M) services billed for 3791 visits to 138 family physicians with the codes assigned by trained research nurses using direct observation. We calculated the degree to which the codes for E&M were concordant with the observer-assigned codes. Analysis of variance and logistic regression were used to examine the association of visit and patient characteristics with discordance between billed and observer-assigned CPT codes. RESULTS: Billing codes were concordant for 55% of encounters. Discordance was evenly distributed between under- and overcoding. Concordance of billed and observed codes was greatest for patients with indemnity insurance. Undercoding increased with longer visit length and a smaller percentage of the visit spent planning treatment. Overcoding was more common during visits with a greater percentage of time spent chatting, planning treatment, and delivering preventive services. CONCLUSIONS: Family physicians are generally accurate in their billing procedures. The findings on patient and visit characteristics associated with over- or undercoding may be used by practicing clinicians to enhance the accuracy of their coding and billing procedures.