Pathology/Lab Coding Alert

Question: When we bill for electron microscopy, can we separately code the toluidine blue stain using 88313?

Louisiana Subscriber

Answer: You should not routinely bill 88313 (Special stains; Group II, all other [e.g., iron, trichrome], except immunocytochemistry and immunoperoxidase stains, including interpretation and report, each) in addition to your bill for electron microscopy (88348, Electron microscopy; diagnostic).

List diagnostic test code: Report 88348 when the pathologist examines ultra-thin sections of tissue using a conventional transmission electron microscope (CTEM). The service includes a written diagnosis and report. You’ll commonly see diagnostic CTEM services with muscle, nerve, or kidney biopsy cases performed by neuropathologists or renal pathology specialists.

You are correct that slides prepared for CTEM typically involve toluidine blue staining. You are also correct that this type of stain falls under the 88313 special stain code for conventional microscopy. That’s because for light microscopy, toluidine blue is not routine, but is a special stain used in unique circumstances such as identifying mast cells in connective tissue to aid in the diagnosis of rheumatoid arthritis.

Different standard for CTEM: For electron microscopy, toluidine blue is the standard stain. The situation is similar to the fact that hematoxylin and eosin (H&E) is the standard stain for tissue preparation for light microscopy. Just as you should not bill a special stain code for H&E staining for light microscopy, you should not routinely bill 88313 for toluidine blue with electron microscopy code 88348.

Note exceptions: Because electron microscopy is an ancillary service to surgical pathology, you’ll often bill 88348 in addition to the code for the primary exam with a code from the range 88302-88309 (Level x --Surgical pathology, gross and microscopic examination …). In some circumstances, you might bill a special stain code such as 88313 for a light microscopy stain.

Medicare’s Correct Coding Initiative (CCI) edits don’t bundle 88313 with 88348, so you should not have a problem reporting the two codes together. But always reporting 88313 with 88348 when toluidine blue is the routine stain for your electron microscopy slides would be inappropriate.