Diagnosis Coding with Diagnostic Testing

Adequate documentation is an essential part of selecting a correct code in any setting. When providers order a test, the information that they document regarding the test results determines the primary and secondary diagnosis codes a coder assigns.

If a physician confirms a diagnosis based on the results of a diagnostic test, code that diagnosis. You may report the signs and symptoms that he or she used to order the test as additional diagnoses, but only under one of the following two circumstances:

• When the signs and symptoms are not fully related to the confirmed diagnosis
• When the physician cannot fully explain the reason for the signs or symptoms

For example, a patient is referred for an abdominal CT scan with a diagnosis of abdominal pain. The CT scan reveals the presence of an abscess. For coding purposes, assign a diagnosis code for "intra-abdominal abscess."

When a patient is referred for a chest x-ray with a diagnosis of "cough," and the chest x-ray reveals a 3 cm peripheral pulmonary nodule, report a diagnosis of "pulmonary nodule" and sequence "cough" as an additional diagnosis.

If the diagnostic test did not provide a diagnosis or if the test comes back normal, code the signs and symptoms that prompted the study.

For example, a patient is referred for a spine x-ray due to complaints of "back pain." A provider performs the x-ray and the radiologist indicates the results are normal. Report a diagnosis of "back pain" because the x-ray results did not show a definite diagnosis.

If the results of the diagnostic test are normal or non-diagnostic and the physician records a diagnosis preceded by words that indicate uncertainty-such as probable, suspected, questionable, working, or rule out-then you should not code the uncertain diagnosis but instead, report the signs or symptoms. Because ICD-10-CM coding guidelines deem diagnoses labeled as uncertain to be unconfirmed, do not report them. This is consistent with the requirement to code the diagnosis to the highest degree of certainty. For example, a patient is referred for a chest x-ray with a diagnosis of "rule out pneumonia." The radiologist interprets the chest x-ray, and the results are normal. Report the sign(s) or symptom(s) that prompted the test (i.e., cough).

Screening tests are performed without the evidence of signs or symptoms of a disease. For patients with a diagnosis or symptom, assign the appropriate ICD-10- CM code (and not a screening code).

When a physician orders a diagnostic test for a patient without signs/symptoms or other evidence of illness or injury, the physician interpreting the diagnostic test should report the screening code as the primary-diagnosis code. Also report any condition discovered during the screening as a secondary-diagnosis code. For example, a patient is referred for a chest x-ray as part of a routine physical. A provider performs the chest x-ray and the results indicate a lung mass. Report the appropriate screening code (in this case, a V code) as the primary diagnosis, followed by a code for the lung mass.

Never list incidental findings as a primary diagnosis. You may, however, report incidental findings as secondary diagnoses. For example, a patient is referred for a chest x-ray because of wheezing. The x-ray is normal except for scoliosis and degenerative joint disease of the thoracic spine. Report wheezing as the primary diagnosis because wheezing was the reason for the patient's visit. You may report other findings as additional diagnoses, such as scoliosis and degenerative joint disease of the thoracic spine.

You may report unrelated and coexisting conditions/diagnoses as additional diagnoses. For example, a patient is referred for a chest x-ray because of a cough. The chest x-ray indicates that the patient has pneumonia. During additional diagnostic tests, you determine that the patient also has hypertension and diabetes mellitus. You would report pneumonia as the primary diagnosis and hypertension and diabetes mellitus as secondary diagnoses.

The key is to read the documentation in the patient’s chart and rely on a version of the standard phrase “If it isn’t documented the patient doesn’t have it”. You don’t want to give the patient a diagnosis that is not consistent with what diagnostic tests have found. Never assume a diagnosis before the results of any tests are in the chart.

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