The ICD-9-CM is the Clinical Modification of the World Health Organization’s International
Classification of Diseases used for diagnostic coding in the United States. ICD-9-CM codes are required under HIPAA for reporting patients’ conditions on insurance claims and encounter forms. Codes are made up of three, four, or five numbers and a description.
Updates of ICD-9-CM codes, called the addenda, are issued twice a year. Medical practices must use the current codes for compliant coding and billing. Current codes are located on the NCHS website at http://www.cdc.gov/nchs/icd9.htm
Two volumes of the ICD-9-CM are used in medical practices: the Tabular List (Volume 1) and the Alphabetic Index (Volume 2). The Alphabetic Index is used first in the process of finding a code. It contains an index of all the diseases that are classified in the Tabular List. These main terms may be followed by related subterms or supported by supplementary terms. The codes themselves are organized into seventeen chapters according to etiology or body system and are listed in numerical order in the Tabular List. A code category consists of a three-digit grouping of a single disease or a related condition. Subcategories have four digits to show the disease’s etiology, site, or manifestation. Further clinical detail is supplied by fifth-digit subclassifications.
The conventions used in the ICD-9-CM must be observed to correctly select codes. Notes provide details about conditions that are either excluded or included under the code. The cross-reference see means that another main term is appropriate. A symbol is used to show a fifth-digit requirement. The abbreviation NOS (not otherwise specified or unspecified) indicates the code to use when a condition is not completely described. The abbreviation NEC (not elsewhere classified) indicates the code to use when the diagnosis does not match any other available code. Parentheses and brackets indicate supplementary terms. Colons and braces indicate that one or more words after the punctuation must appear in the diagnostic statement for the code to be applicable. Codes that are not used as primary appear in italics and are usually followed by instructions to code first underlying disease or use additional code.
V codes identify encounters for reasons other than illness or injury and are used for healthy patients receiving routine services, for therapeutic encounters, for a problem that is not currently affecting the patient’s condition, and for preoperative evaluations.
E codes, which are never used as primary codes, classify the injuries resulting from various environmental events.
The three steps in the coding process are to (a) determine the reason for the encounter that is the patient’s primary diagnosis, (b) locate the medical term in the Alphabetic Index, and (c) verify the code in the Tabular List.
Three key coding guidelines are to (a) code the primary diagnosis first, followed by current coexisting conditions, (b) code to the highest degree of certainty, never coding inconclusive, rule-out diagnoses, and (c) code to the highest level of specificity, using fifth digits or fourth digits when available.
