Pathology/Lab Coding Alert

You Be the Coder:

Multiple FISH Probes Define 'Multiplex'

Published on Tue Apr 07, 2015

Question:Could you please clarify the meaning of “multiplex” in codes 88374 and 88377 for FISH? I’ve been told it means that the test is an FDA approved kit, but I’m not sure if that’s correct.

Tennessee Subscriber

Answer: “Multiplex” essentially means multiple. So a fluorescence in situ hybridization (FISH) test that requires two or more probes in a single procedure to provide a specific clinical diagnosis is a multiplex test.

Here’s how it works: For these multiplex FISH tests, the lab analyst can typically evaluate the multiple probes simultaneously, because as each probe generally involves a distinct color signal, all of which the analyst can observe at the same time. When you report this service, you should select one of the following codes based on whether the pathologist manually evaluates the slide, or uses a computer-assisted technology to evaluate the FISH probes:

88374 — Morphometric analysis, in situ hybridization (quantitative or semi-quantitative), using computer-assisted technology, per specimen; each multiplex probe stain procedure
88377 — Morphometric analysis, in situ hybridization (quantitative or semi-quantitative), manual, per specimen; each multiplex probe stain procedure.

Although labs may use an FDA approved multiplex FISH kit, that is not the criterion for selecting a multiplex FISH code such as 88374 or 88377 instead of one of the single-probe codes.