What does Modifier 91 indicate in laboratory testing?

Modifier 91 is used in laboratory testing to indicate that the same laboratory test was repeated on the same day. This modifier is specifically applied when there is a need to run the same test multiple times to obtain additional information, confirm a result, or account for variability in a patient's condition.

When Modifier 91 is appended to the procedure code for the test, it clarifies that the tests are not duplicates and that each instance of the test is necessary for a valid reason, such as monitoring a patient's progress or verifying abnormal findings. This distinction is important for billing and reimbursement, as it ensures that the laboratory's repetitive efforts are appropriately recognized and compensated for.

Other options do not accurately describe the purpose of Modifier 91. For example, Modifier 91 does not apply to tests performed by different laboratories, denote a first-time procedure, or indicate inconclusive results. Each of those scenarios would utilize different modifiers or coding practices specific to their context.