What modifier should be applied when indicating that a professional service was discontinued before completion?

The appropriate modifier to apply when indicating that a professional service was discontinued before completion is the -53 modifier. This modifier is specifically used to designate that a procedure or service was aborted or terminated due to extenuating circumstances that prevented its completion.

In medical billing and coding, the -53 modifier helps convey to insurers that although the service was initiated, it could not be finished for valid reasons, such as patient safety, changes in the patient's condition, or other unforeseen events during the procedure. By using this modifier, healthcare providers can ensure that they receive appropriate reimbursement for the portion of the service that was delivered, even if not all intended aspects could be completed.

Other modifiers do not represent the same concept; for example, the -25 modifier indicates a significant, separately identifiable evaluation and management service provided on the same day as another procedure, while the -74 modifier is used when a surgical procedure was terminated after the induction of anesthesia, but before the start of surgery. The -91 modifier is applied in cases of repeated laboratory tests. Therefore, the -53 modifier is the correct choice for denoting a discontinued service.