Answer: The appropriate diagnosis code is either the reason for the test being ordered or the results of the test, as long as the reason for ordering the test is not "screening."
Medicare pays for the code that describes the outcome of the test as the primary diagnosis. For example, if the patient came in with wheezing and the test determines that the patient was having an acute exacerbation of asthma, you could report 493.02 (Extrinsic asthma; with acute exacerbation) as the primary diagnosis with 786.07 (Wheezing) as the secondary diagnosis.
Medicare prohibits you from reporting any other diagnosis as the primary diagnosis when the original intent was screening, even when the final outcome of the test uncovered a problem or condition. So if the patient did not present with any symptoms and had no personal history of cardiopulmonary conditions but had only a family history of emphysema, the test would be ordered as a screening service (V81.3).
Be aware that only certain circumstances and diagnosis codes will support medical necessity. Documentation should be included to support the test as medically necessary. Local medical review policies spell out in-depth the requirements that must be met for full reimbursement.
For example, the New York state medical review policy says that lung function tests are appropriate under five circumstances:
To determine the presence of lung disease or abnormality of lung function
To determine the extent of abnormalities and the causative disease process
To determine the extent of disability due to abnormal lung function
To determine the progression of the disease
To determine the type of disease or lesion.
Medicare excludes screening as an indication for lung function testing from reimbursement and will not reimburse for screening testing. It defines screening as a PFT performed on an asymptomatic patient, with or without high risk of lung disease, without any pre-existing cardiopulmonary condition; studies as part of a routine exam; and studies as part of an epidemiological survey. For example, diagnosis codes that are not covered include many V codes:
V70.0 Routine general medical examination at a health care facility
V76.0 Special screening for malignant neoplasms of respiratory organs
V81.3 Special screening for chronic bronchitis and emphysema
V72.82 Preoperative respiratory examination
Surveys and clinical research (V70.6, V70.7).
Be sure to check with the carrier to determine acceptable diagnosis codes to support medical necessity. There are several examples of appropriate ICD-9 codes that will support medical necessity for PFTs:
162.0-162.9 Malignant neoplasm of trachea, bronchus, and lung
466.0 Acute bronchitis
492.0-492.8 Emphysema
493.00-493.92 Asthma
518.81 Acute respiratory failure
780.50-780.57 Sleep disturbances
786.2 Cough
790.91 Abnormal arterial blood gases.
Don't be tempted, however, to choose one of the above diagnosis codes just because insurers will pay. Fraud penalties are worse than write-offs. With each claim, you must present documentation that supports medical necessity and shows support for the appropriate ICD-9 codes. All studies require an interpretation with a written report. Computerized reports must have a physician's signature. Providers of PFTs must have on file a referral (prescription) with clinical diagnoses and requested tests. You should have all documentation available for Medicare upon request.
