Which coding manual serves as a reference for physiological tests and studies?

The CPT codebook is the correct reference for physiological tests and studies because it is specifically designed to provide the codes for a wide range of healthcare services, including evaluation and management, surgical procedures, and various diagnostic services. Within the CPT codebook, there is a dedicated section for laboratory and pathology services, which encompasses physiological tests and studies, reflecting the comprehensive range of medical practices that can be coded.

In contrast, the ICD codebook focuses primarily on diagnosis codes rather than procedural coding, while the HCPCS manual includes codes for supplies, services, and procedures not covered by the CPT. The Revenue Cycle Management manual deals more broadly with financial processes and does not provide detailed coding specifically for physiological tests and studies. Thus, the CPT codebook stands out as the authoritative source for coding these specific healthcare activities.