Which statement correctly describes the difference between ICD-10-CM codes and CPT/HCPCS codes and how they interact on a claim?

• A. CPT/HCPCS codes identify diagnoses; ICD-10-CM codes describe the services or procedures performed.
• B. ICD-10-CM codes identify diagnoses; CPT/HCPCS codes describe the services or procedures performed.
• C. ICD-10-CM codes identify diagnoses or reasons for the visit; CPT/HCPCS codes describe the services or procedures performed. A claim must pair a billing diagnosis with the service codes to establish medical necessity and payment eligibility.
• D. ICD-10-CM and CPT/HCPCS codes both identify diagnoses.

Answer: (C)

The key idea is that diagnoses and services are two different pieces of information that must come together on a claim. ICD-10-CM codes identify the reason for the encounter—the patient’s diagnoses or conditions being treated—while CPT/HCPCS codes describe what was actually done—the procedures, services, or supplies provided.

On a claim, you pair the diagnosis code with the service codes to show medical necessity. Payers look for that link: the diagnosis justifies why the specific service was performed, and the CPT/HCPCS code communicates what was done and at what level of detail. This pairing helps determine eligibility for payment and whether the service is reasonable and covered.

For example, a patient visiting for chest pain might have a primary diagnosis code for chest pain and a CPT code for an ECG or an office visit. The service code needs to be supported by the diagnosis to be payable; without a matching diagnosis, the claim can be denied for lack of medical necessity.

So, the correct statement reflects that ICD-10-CM codes identify diagnoses or reasons for the visit, CPT/HCPCS describe the services or procedures performed, and a claim must pair them to establish medical necessity and payment eligibility.