As you know, coding is a uniform classification system that translates verbal or written descriptions into numbers to maintain and regulate health care data.

Health care providers and health insurance companies deal mainly with two primary code sets: ICD-9-CM is used for all diagnosis and inpatient procedure coding in the United States, while CPT-4 is used for outpatient procedures and physicians’ services coding.

ICD-9-CM Coding

These codes are divided into three volumes—which just happen to be numbered volumes 1, 2 and 3:
   

• Volume 1 contains the alphabetical index of diagnoses
• Volume 2 contains a numerical index of diagnosis codes (001.0 – V85.4)
• Volume 3 contains an alphabetical index of procedures and a numerical listing of procedure codes
• And—there’s also a special addendum of E-codes

To correctly assign a diagnosis code, you must follow three steps:
 

1. Review the documentation.
2. Code all diagnostic information that has an impact on the current treatment, including the patient’s medical history.
3. Always assign codes to the highest degree of specificity.

Tips about coding, code specificity and coding patient history 

• The diagnosis chiefly responsible for the patient encounter should be sequenced first.
• Codes described as “unspecified” or “not elsewhere classified” are allowable if that code is the most specific code available in ICD-9-CM.
• Review the documentation for any applicable encounter codes, screening codes and/or status codes (V-codes) such as “encounter for fitting and adjustment of intestinal appliance” or “screening for malignant neoplasm of colon”.
• Review the code to see if there’s a fourth or fifth digit. Most codebooks have a note in the margin to indicate that a more specific code is available.
• Watch out for the inclusion of notes such as excludes, includes or code also.
• Do not code diagnoses that have been documented as probable, suspected, ruled out or versus. These differential diagnoses can’t be applied to a specific outpatient encounter.
• When the documentation states “history of…”, then any code assigned to that diagnosis must be a history code.
• For ER services, code signs and symptoms along with final diagnosis. This will ensure the claim identifies the reason the patient presented in the ER according to prudent layperson guidelines.

• Certain CPT codes, like evaluation and management codes, are based upon the amount of time a physician spends with a patient. Carefully review the documentation to make sure it supports the CPT code you wish to assign—especially if the CPT-code is time-based.
• Avoid assigning CPT codes described as “unlisted procedure” whenever possible. Usually, these codes end in “99”.
• TRICARE demands that a procedure code is directly supported by a diagnosis code. When a diagnosis code doesn’t directly support a procedure code, it will often result in an R6CRX denial.

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Last Reviewed:  June 14, 2007