Definition - The “-91” modifier is used to indicate a repeat laboratory procedural service on the same day to obtain subsequent reportable test values. The physician may need to indicate that a lab procedure or service was distinct or separate from other lab services performed on the same day. This may indicate that a repeat clinical diagnostic laboratory test was distinct or separate from a lab panel or other lab services performed on the same day, and was performed to obtain subsequent reportable test values.
Rationale - Multiple laboratory services provided to a patient on one day by the same provider may appear to be incorrectly coded, when in fact the services may have been performed as reported. Because these circumstances cannot be easily identified, a modifier “-91” was established to permit claims of such a nature to bypass correct coding edits. The addition of this modifier to a laboratory procedure code indicates a repeat test or procedure on the same day.
Instruction - The additional or repeat laboratory procedure(s) or service(s) must be identified by adding the modifier “-91”.
When cytopathology codes are billed, the appropriate CPT code to bill is that which describes, to the highest level of specificity, what services were rendered. Accordingly, for a given specimen, only one code from a family of progressive codes (subsequent codes include services described in the previous CPT code, e.g., 88104-88107, 88160-88162) is to be billed. If multiple services on different specimens are billed, the “-91” modifier should be used to indicate that different levels of service were provided for different specimens. This should be reflected in the cytopathologic reports.