Answer:
CPT is what was done, the ICD is why it was done. Insurance companies, especially Medicare and Medicaid have procedures that they will not cover if you don’t attach an acceptable diagnosis code. Fortunately, this isn’t a secret. They publish documents that outline what the procedure(s) are and what the needed or ‘covered’ diagnoses are.
Most of the links are self evident. Broken arm diagnosis - fix broken arm CPT code. Other pairings are also as easy.
It has gotten more difficult with ICD-10 because the available number of diagnoses has expanded tremendously. For some insurance companies it was an opportunity to narrow down the covered diagnoses for some of the more expensive procedures.
Modifiers have special use in coding. They can be informative; there are modifiers for each of your fingers and each of your toes. They can affect your reimbursement for the procedure performed: there are modifiers for services that were not completed. There are modifiers that will allow you to bill some things you wouldn’t be able to normally; modifiers for the same surgery done at different sites. Modifiers go on the CPT codes, not the diagnosis codes. Some modifiers are only for physician visits, some only for surgery. There are many, and using them is an art form.
Explanation: