What is necessary before entering the procedure codes in the Services form?

Filling in the diagnosis is essential before entering the procedure codes in the Services form because the diagnosis provides the medical justification for the procedures that will be performed. This linkage is crucial for appropriate billing and coding, as procedure codes must accurately reflect the nature of the patient's condition as diagnosed. Additionally, insurance companies often require this correlation to approve claims, ensuring that the services provided are deemed necessary based on the patient's diagnosis.

The other options, while important in their own right, do not directly establish the required connection between the diagnosis and the procedure codes. Obtaining patient consent is vital for ethical and legal reasons, but it does not directly influence the coding process. Similarly, reviewing past medical history can aid in understanding the patient's condition but does not replace the need for a current diagnosis. Confirming insurance eligibility is crucial for billing purposes but occurs after ensuring that the services are supported by an appropriate diagnosis. Thus, the diagnosis stands out as the necessary starting point for accurate procedure coding.