What does modifier QW indicate?

The modifier QW is specifically used to indicate that a laboratory test is a CLIA (Clinical Laboratory Improvement Amendments) waived test. CLIA waivers are granted to simple tests that are easy to perform and carry a low risk of error, thus allowing them to be conducted in a wider range of environments, including patient homes and physician offices, without the need for a complex laboratory setup.

When claims with this modifier are submitted, it signals to payers that the laboratory procedures performed meet the criteria for CLIA waiver status, which is essential for reimbursement. This modifier ensures that laboratories comply with regulatory standards while facilitating easier access to necessary diagnostic testing for patients.

The other answer choices refer to different concepts in the context of medical billing and auditing. Reference laboratory testing, for example, describes procedures performed by labs that specialize in certain tests, and medical necessity concerns whether a test is appropriate and justified based on the patient’s diagnosis. Repeating a test for clinical reasons relates to following up on previous results but does not pertain directly to the function of the QW modifier.