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Here's how to tell whether the diagnosis codes you submit are specific enough to be reimbursable.

Fam Pract Manag. 2000;7(9):16

More and more payers, including Medicare, are denying or delaying payments for claims that aren't coded to the highest possible degree of specificity. To help you prevent this type of reimbursement slowdown, here's a quick refresher:

Although ICD-9 is full of them, three-digit codes are seldom reimbursable. In most cases, three-digit ICD-9 codes identify diagnostic categories, and they should be used only if there is no four-digit code (ICD-9 refers to these as “diagnostic subcategories”) within the category.

Some physicians assign a three-digit code when a specific diagnosis is not clear at the time of the initial encounter. Even under these circumstances, a four-digit or five-digit code must be used. For example, if a physician concludes that a patient has allergic rhinitis (diagnostic category 477) but has not yet determined the specific allergen, he or she should submit the four-digit code for “cause unspecified” (477.9).

When the fourth digit is a zero following a decimal point, don't make the mistake of assuming that it has no value. The zero provides specific information. For example, the zero in 595.0 represents acute cystitis and differentiates it from 595.1 and 595.2, which represent chronic forms of cystitis.

Four-digit codes should be used only if there is no fifth-digit subclassification for the category. For example, ICD-9 provides a fifth-digit subclassification for use with the diagnostic category for migraine (346) and instructs users to extend the four-digit codes for classical migraine (346.0), common migraine (346.1), etc., to five digits. A “0” or a “1” must be added to connote “without mention of intractable migraine” or “with intractable migraine, so stated,” respectively.

Of course there's more to accurate diagnosis coding than making sure you have the right number of digits. To establish medical necessity, you should link diagnosis codes (as many as four) to each CPT code you submit. You also should be sure to code the primary diagnosis (the main reason for the visit) first, followed by any others. Finally, don't code the following types of diagnoses:

  • Those that are no longer being treated;

  • Those that don't affect the patient's treatment or management at that visit;

  • Rule-out, suspected, questionable or probable diagnoses.

A tool for easier diagnosis coding

This article includes “ICD-9 Codes for Family Medicine: The FPM Long List,” a list of about 1,500 codes common in family medicine. The list was developed by Allen Daugird, MD, MBA, and Donald Spencer, MD, MBA, both family physicians and clinical associate professors at the University of North Carolina, Chapel Hill, and Philip S. Whitecar, MD, assistant professor of family medicine at Wright State University, Dayton, Ohio.

The long list is an expanded version of a popular resource that was developed by Drs. Daugird and Spencer, first published in FPM in 1996 and now referred to as “The FPM Short List.” It includes about 600 codes.

The long list was created in response to comments from readers that their insurers insist on four-digit and five-digit accuracy. It replaces many of the “unspecified” and “NOS” (not otherwise specified) codes with more specific alternatives. It also includes more codes useful for hospital care.

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