Final answer:
The coder must assign the correct ICD codes for both the primary condition and the co-existing condition to ensure comprehensive patient care, support medical necessity, and enable accurate billing and reimbursement.
Step-by-step explanation:
When a patient has a co-existing condition that the physician diagnoses and treats, the coder must assign the appropriate International Classification of Diseases (ICD) codes for both the primary condition and the co-existing condition. This is critical for several reasons: it ensures that patient care is comprehensive, supports the medical necessity of services provided, and it allows for accurate billing and reimbursement. For example, if a patient is being treated for a viral infection and they also have diabetes, the medical coder must use ICD codes to reflect both the viral infection and the diabetes.
ICD codes are also important for acquiring the necessary laboratory tests to confirm a diagnosis and for health-care management systems to verify treatments. Medical coders and billers use these codes to process insurance claims, and vital-records keepers use them for recording causes of death.