Compliance Corner

My laboratory is confused about the application of the modifiers 59 and 91 for laboratory services. Can you briefly explain how each should be used? Both modifiers are used to report a repeat test or Current Procedural Terminology code performed on the same date of service when the repeat test is medically necessary. The modifier 91 is to be used when the same exact test is performed more than once on the same day. For instance, a blood glucose is performed in the morning, and the result is abnormal. The patient is treated and later in the day, a second glucose is performed to determine if the treatment was effective. The 59 modifier is used when the repeat test is either a different test, a different specimen, or is taken from a different site. This modifier can be used to bypass correct coding initiative (CCI) pairs and medically unlikely edits (MUE) units of service that exceed the allowed amount. The 59 modifier must be used judiciously and documentation must be maintained to support the medically necessary reason for bypassing the CCI and MUE edits.