Modifiers for repeat lab and pathology services.

When is it appropriate to use the 76 modifier vs. the 91 modifier?

Modifier 91

Modifier -91 should be appended to laboratory procedure(s) or service(s) to indicate a repeat test or procedure on the same day. This modifier indicates to the carriers or fiscal intermediaries that the physician had to perform a repeat clinical
diagnostic laboratory test that was distinct or separate from a lab panel or other lab services performed on the same day, and was performed to obtain medically necessary subsequent reportable test values. This modifier should not be used to report repeat laboratory testing due to laboratory errors, quality control, or
confirmation of results.