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ICD Coding Overview
For outpatient coding, the ICD code book consists of 4 main areas:
-Volume 1 or Tabular index (CODES)
-Volume 2 or Alphabetical index (INDEX)
-Table of Drugs and Chemicals (DRUGS)
-Table of Neoplasms (NEOS)

In addition, Flash Code provides hospital based coders access to:

Volume 3 - Hospital Procedures
DRG classification and ICD code cross references

There are over 15,000 individual ICD codes in volume 1, listed by Chapter, Subchapter, then by codes in numerical order. Since only coding savants can remember all of these codes this way, there is an alphabetical listing-Volume 2. There are over 75,000 listings in the alpha index. Many entries contain information that points to the ICD code, but does not form a portion of the actual diagnosis text. For example, the alpha index term 'uvulitis' references code 528.3 'cellulitis and abscess of oral soft tissues'.

The table of Drugs and Chemicals contains a list of over 4,500 products that reference ways in which that product impacted the patient's diagnosis (Poisoning, Accident, Therapeutic use, etc). Many entries are very specific names and correlate to a more general term in the CODES section. For example 'dilantin' in the table correlates to 'phenytoin derivatives' as part of the diagnosis text.

The table of Neoplasms contains a listing of over 1,700 sites of neoplastic growths. These are classified as either malignant, benign, of uncertain behavior, or unspecified. Once again, there are specific entries in this table that correlate to more general diagnoses. Neoplasms of 'white matter' cross reference the brain and its stuctures, without mentioning white matter specifically

Note that the purpose of using the alpha index, and both tables is to find diagnoses, from these reference areas first, then finalize the full diagnosis in the CODES (Volume 1) file last. The ICD codes are grouped into families of codes within 3 digit classifications. All but 146 3 digit classification codes contain a family of four digit subclassification codes, many of these contain additional families represented with 5th digit codes. Any code that contains a level of codes beyond it is considered to be a non-specific code and will not be accepted for billing. For example:

Code 460-Acute Nasopharyngitis is billable since there are no codes for this family beyond the 3 digit classification
Code 493-Asthma has not only fourth digit codes (493.0 Extrinsic Asthma, 493.1 Intrinsic Asthma, etc) but also fifth digit codes (493.00 Extrinsic Asthma with Status Asthmaticus, and etc)

We have chosen to use the concept of driving a car so that you can 'go until you reach the most specific code.' Once you reach the 3 digit classification codes, each code number is listed with either a green light or a red light. Green lights represent an intersection you must pass through on you way to more codes that must be reviewed in order to successfully bill. Red light codes represent codes that are at the end of the 'drive' and have no additional code intersections beyond them.

CMS produces the ICD-9-CM Guidelines for Coding and Reporting that goes into significant detail on coding from the alpha index, tables, and Volume 1 chapters. You can download a copy of that here.