Pathology/Lab Coding Alert

-59 or -91 tells the whole story

If your lab performs the same test twice or performs two tests that yield similar results, payers typically don't want to cover both services. But if you know when to append modifiers -59 and -91, you could win deserved pay for your pathologist's work.

Sometimes physicians find it medically necessary to carry out repeat or bundled tests, and that's when you'll need to know about modifiers -91 (Repeat clinical diagnostic laboratory test) and -59 (Distinct procedural service) to get paid for your work, says Elizabeth Sheppard, HT (ASCP), manager of anatomic pathology at Wake Forest University Baptist Medical Center in Winston Salem, N.C.

Use -91 for Repeat Clinical Lab Tests

If your lab repeats the same clinical diagnostic test because the physician requires sequential results for medical purposes, you should report the second and each subsequent code with modifier -91.

Example: The physician orders a potassium test three times during the day to monitor the patient's response to potassium replacement therapy. "Report 84132 (Potassium; serum) for the first test, and 84132-91 for each of the subsequent tests," Sheppard says.

You should also use -91 if the lab performs a panel of tests, and then performs one component of the panel later in the day for medically necessary reasons.

Case in point: The lab performs a renal function panel (80069, Renal function panel), and the physician orders a follow-up blood gas for carbon dioxide later in the day. "You should report the subsequent blood gas as 82374-91 (Carbon dioxide [bicarbonate])," says Kenneth Wolfgang, MT (ASCP), CPC, CPC-H, CEO of Chargemaster Maintenance Services, a laboratory consultation company in Portland, Ore.

Watch out: Don't report modifier -91 if the lab repeats a test due to testing problems or to confirm initial results. "Payers don't cover these types of quality-assurance reasons for repeating a test," Sheppard says.

Sometimes a more specific code describes a series of repeat lab tests. In those cases, you should always report the more specific code, not multiple units of the repeated test code with modifier -91. For instance, report a glucose tolerance test as 82951 (Glucose; tolerance test [GTT], three specimens [includes glucose]), not as three units of 82947 (Glucose; qualitative, blood [except reagent strip]) with modifier -91.

Report -59 for Bundled Services

When two services provide similar diagnostic information, payers say that the codes are "bundled," and they won't pay for both tests for the same patient on the same day. "Code bundles include tests that are a component of a more comprehensive test, or tests that have different methods for reaching essentially the same results," Sheppard says.

Medicare's National Correct Coding Initiative (NCCI) edits are the largest and most widely used list of bundled services. Updated quarterly, NCCI edits catalog hundreds of code pairs that lab coders should not report together. 

Example: If the lab prepares an FNA breast lesion specimen as both direct smear and thin-layer preparation slides, you should not report two separate codes for the service. The code for an FNA exam is 88173 (Cytopathology, evaluation of fine needle aspirate; interpretation and report), and the code for a nongynecological thin-layer preparation exam is 88112 (Cytopathology, selective cellular enhancement technique with interpretation [e.g., liquid-based slide preparation method], except cervical or vaginal), but NCCI edits prohibits billing the two codes together.

Do this: "Only if you performed an FNA on the breast lesion and a thin-layer preparation on a separate non-gyn
specimen, such as bronchial washing, should you report 88173 and 88112 together," Wolfgang says. In that case, you should append modifier -59 to the NCCI column 2 code, which is 88112.

List -59 for Multiple Surgical Pathology Specimens - Sometimes

Pathologists may examine multiple tissue specimens from the same patient on the same day, possibly requiring you to report multiple units of the same surgical pathology exam code. For example, the pathologist may receive three separately identified skin lesions from different body sites.

What to do: This much is for sure - you should report three units of 88305 (Level IV - Surgical pathology, gross and microscopic examination, skin, other than cyst/tag/debridement/plastic repair). But how you explain that each code represents a separate service depends on your payer. "Many Medicare carriers and other payers require you to report each additional specimen with modifier -59, but some payers just require you to list 88305 x 3 to indicate multiple specimens," Sheppard says.

In some rare instances, carriers require modifier -76 (Repeat procedure by same physician) for multiple surgical pathology specimens.

Bottom line: Report multiple surgical pathology specimens according to your carrier's instructions. "If you are getting denials from your carrier, call them to find out what they will accept for additional specimens. Just be sure to get the instructions in writing and to apply the coding consistently," Sheppard says.

Don't Confuse -59 and -91

If the lab repeats a clinical lab test for some reason other than to obtain subsequent test values, then you shouldn't use modifier -91. You should report multiple cultures taken from different wound sites, for example, with modifier -59, not -91, even though the culture code is a clinical lab test.

Although it's confusing, cultures taken from different sites represent a "distinct procedural service," not a "repeat clinical diagnostic laboratory test." That means you should report the first culture as 87070 (Culture, bacterial; any other source except urine, blood or stool, aerobic, with isolation and presumptive identification of isolates) and each culture from a different site as 87070-59.