Coding for Diagnoses (ICD-9-CM)

When billing for services provided by a physical therapist, it will be necessary to specify the diagnosis that is being treated. For billing purposes, it is necessary to include the medical diagnosis that may differ from the impairment-based diagnosis described in the Guide to Physical Therapist Practice Patient/Client Management Model.

Determining which ICD-9-CM code to select for billing purposes can be a challenge. It is suggested that you select a code that most accurately describes the condition you are treating based on the objective evidence. If you are treating two or more separate conditions, be sure to include all the applicable codes and specify which interventions apply to each diagnosis listed.

Payment policy of an individual payer may impact which ICD-9-CM code should be chosen. If you have any questions, call the payer in advance of sending your claim to discuss whether specific ICD-9-CM codes are reimbursable for physical therapists. Your goal is to maximize the number of claims that are paid on the first submission and to minimize the need for appeals.

APTA has received numerous inquires of late, regarding ICD-9-CM coding. Members report that their claims are being denied due to "invalid diagnosis code." Many of the diagnoses now require a fourth or fifth digit to the diagnosis code. The requirement for the extra digit became effective on October 1, 2003.

A therapist must use the most specific code available. "Assign three-digit codes (category codes) if there are no four-digit codes within the category. Assign four-digit codes (subcategory codes) if there are no five-digit codes for that category. Assign five-digit codes (fifth-digit subclassification codes) for those categories where they are available." (ICD-9-CM 2004, Volumes 1 and 2. Ingenix Publishing Inc, 2003. Introduction, page 3.)

Ingenix is the primary publisher of the International Classification of Diseases (ICD-9-CM) code manuals. These books, plus many other coding and reimbursement products can be obtained by visiting or calling 800.INGENIX, option 1.

The National Center for Health Statistics (NCHS), a division of the Center for Disease Control and Prevention, compiles statistical data to facilitate actions and policies to improve health.  This agency is a critical element of public health and health policy and is the driving force behind classification of diseases (ICD-9). 

For more information on NCHS, go to