Seven Tips to Improve Your ICD-9 Coding for Diagnostic Tests


You can prevent costly claims denials by following these guidelines.

Fam Pract Manag. 2002 Feb;9(2):16.

The Centers for Medicare & Medicaid Services (CMS) recently issued instructions clarifying current diagnosis coding guidelines for reporting diagnostic tests (available online at Although intended for Medicare carriers, the instructions serve as a good reminder to physicians. Here’s a summary:

1. Code the confirmed diagnosis whenever possible. If you have confirmed a diagnosis based on the results of the diagnostic test, you should code that diagnosis.

2. If there’s no confirmed diagnosis or the results are normal, code the signs and symptoms that prompted you to order the test. For example, you see a patient in your office for chest pain and do an EKG. The EKG is normal, and the final diagnosis is chest pain due to suspected gastroesophageal reflux disease (GERD). The primary diagnosis code for the EKG should be chest pain, because the EKG was normal and you did not determine a definitive cause for the chest pain. Because the ICD-9 coding guidelines consider diagnoses labeled as uncertain (e.g., probable, suspected, questionable, rule out or working) to be unconfirmed and, thus, not reported, you should not use suspected GERD as a diagnosis.

3. Never list incidental findings as primary diagnoses. You should report incidental findings as secondary diagnoses only. For example, a patient presents to you because of wheezing, and you do a chest X-ray. The X-ray is normal except for scoliosis and degenerative joint disease of the spine. In this case, you report wheezing as the primary diagnosis since it was the reason for the patient’s visit, and you may report scoliosis and degenerative joint disease of the spine as secondary diagnoses.

4. Report unrelated and coexisting conditions/diagnoses as secondary diagnoses. For example, an established patient presents with a cough, and the result of the ensuing chest X-ray indicates the patient has pneumonia. The patient also has chronic hypertension and diabetes mellitus. In this case, you report a primary diagnosis of pneumonia. You may also report the hypertension and diabetes mellitus as secondary diagnoses.

5. Code to the highest degree of specificity. In the context of ICD-9 coding, the “highest degree of specificity” refers to the code that most fully explains the narrative description of the symptom or diagnosis. For example, if a chest X-ray reveals a primary lung cancer in the left lower lobe, you should report the ICD-9 code 162.5 for malignancy of the left “lower lobe, bronchus or lung,” not the code for a malignancy of “other parts of bronchus or lung” (162.8) or the code for “bronchus and lung, unspecified” (162.9).

6. Code to the correct number of digits. Remember that ICD-9 diagnosis codes have three, four or five digits. Codes with three digits are included in ICD-9 as the heading of a category of codes that may be further subdivided by the use of fourth and/or fifth digits for greater specificity. Assign three-digit codes only if there are no four-digit codes within that code category. Assign four-digit codes only if there are no five-digit codes for that category. Assign five-digit codes where they exist.

For example, if you see a patient with diabetes mellitus, it would be incorrect to assign code 250 since all codes in this series have five digits. The fourth and fifth digits of the code vary depending on the patient’s condition. If the type of diabetes is not specified and there is no indication that the patient has a complication or that the diabetes is not under control, the correct ICD-9 code would be 250.00.

7. If you order a diagnostic test in the absence of signs/symptoms or other evidence of illness or injury, use the appropriate “screening” diagnosis code. The primary ICD-9 diagnosis code should reflect that it is a screening test (e.g., V76.11, “Screening mammogram for high-risk patient”). The results of the test, if reported, may be recorded as additional diagnoses.

Other thoughts

If any of the above seems like “news” to you, then you might want to devote some time to improving your diagnosis coding skills. For help, see “Improve Your ICD-9 Coding Accuracy,” FPM, July/August 1999, page 27.

Kent Moore is the AAFP’s manager for health care financing and delivery systems and is a contributing editor to FPM.

Conflicts of interest: none reported.

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Copyright © 2002 by the American Academy of Family Physicians.
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