Pathology/Lab Coding Alert

Complex coverage issues impact coding and reimbursement for lab tests used to diagnose and monitor thyroid disorders. Medical-necessity indications, as well as frequency limits and recent clinical advances in laboratory methods, dictate reporting requirements for these services.

"Not only do many Medicare carriers have local medical review policies (LMRPs) that govern coverage, but a thyroid testing national coverage decision will become effective in November of this year," says William Dettwyler, MT-AMT, coding analyst for Health Systems Concepts, a laboratory coding and compliance consulting firm in Longwood, Fla. Coupled with national Correct Coding Initiative (CCI) edits, these rules impact payment for thyroid testing services based on diagnosis and procedure coding.

Know Indications for Thyroid Function Tests

Thyroid function tests are indicated to define thyroid disease of over- or underproduction of hormones. Medicare and many third-party payers consider thyroid testing reasonable and necessary to 1) confirm or rule out primary hypothyroidism or hyperthyroidism, 2) distinguish between primary and secondary hypothyroidism, 3) monitor progression of disease and therapy in patients with thyroid dysfunction, and 4) monitor neoplasm of the thyroid or other endocrine glands.

Physicians often order thyroid function tests when clinical signs and symptoms indicate possible abnormalities of the thyroid or pituitary glands.

"Many indistinct clinical complaints may arouse a suspicion of thyroid dysfunction, so Medicare and most insurers allow certain thyroid tests based on a long list of ICD-9 symptom codes," Dettwyler says. These include symptoms described throughout the ICD9 Codes, such as malnutrition (263.0-263.9), depression (311), constipation (564.0x), and dysmenorrhea (625.3). Many insurers also pay for thyroid function tests based on codes from ICD-9's "symptoms, signs, and ill-defined conditions" section (780-799), such as insomnia (780.50-780.52), abnormal weight gain or loss (783.1 or 783.2x), palpitations (785.1) or nervousness (799.2).

"Thyroid function tests are not covered for screening, so you should report any of these signs and symptoms described by the ordering physician as the reason for the test, no matter how vague they may seem," Dettwyler cautions. Commonly covered thyroid tests for these diagnoses include:

These tests are also covered for confirmed thyroid or other endocrine system diagnoses, such as neoplasm (e.g., 193, 194.8, 198.89, 226), goiter (240-241), hypothyroidism (243-244), and other thyroid disorders (e.g., 246). "The national coverage policy and many individual LMRPs and private insurers provide an exhaustive list of acceptable diagnoses to indicate medical necessity for thyroid function tests," Dettwyler says.

Specific ICD-9 coding guidelines exist for thyroid function tests ordered for situations such as monitoring disease or medication. For example, when a thyroid function test is ordered to monitor response to medication, report V58.69 (Long-term use of other medications) as the reason for the test. When a thyroid test is ordered to follow up a patient who is no longer being treated for a "covered" disease, report the appropriate code from the V67.x category (Follow-up examination).

When the reason for the thyroid test is an ICD-9 manifestation symptom (appearing in italics in the ICD-9 tabular list), report first the underlying condition. For example, thyrotoxic exophthalmos (376.21) is a manifestation code that must be sequenced after the underlying condition, such as Graves' disease (242.0).
 

Medicare limits thyroid function testing to two times a year in clinically stable patients, with more frequent testing considered for symptomatic patients or those with altered thyroid therapy based on appropriate documentation. Until the national coverage rule is effective in November 2002, consult LMRPs (available at www.lmrp.net) for definitive frequency guidelines in your area.

Understand Lab Methods

"The serum levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4) are instrumental in diagnosing hyperthyroidism or hypothyroidism," says Diane Liles, MT (ASCP), a laboratory manager at Penrose-St. Francis Laboratory in Colorado Springs, Colo. After a diagnosis of thyroid dysfunction, further testing is often ordered to determine the etiology of the disorder and to monitor treatment.

Clinical advances in thyroid testing methods have changed the protocols for many labs, often reducing the number of tests required to diagnose and monitor thyroid dysfunction. For example, laboratories historically estimated the patient's FT4 serum levels by running two tests, such as total thyroxine (84436) and triiodothyronine (T3) uptake (84479). The results were used to calculate the free thyroxine index (FTI), which provides an indirect proportional estimate of FT4. "These two tests comprised the thyroid panel (80091) that was deleted in CPT 2000," Liles says.

Less commonly, some labs calculated FTI based on the results of a TT4 assay (84436) and a test for thyroxine binding globulin (TBG) (84442), which is a protein that "binds" thyroxine in the blood. This method of estimating FT4 is now rarely used.

"Free thyroxine is now more accurately measured by a direct assay utilizing methods such as equilibrium dialysis," Dettwyler says. A direct measure of serum FT4 is reported with 84439. "When a physician orders the FT4 direct assay (84439), it would be unusual to concurrently order an FTI calculated from the TT4 (84436) and T3 uptake (84479) because it would provide similar information," he explains.

"However, sometimes physicians will still order all three of these tests [84439, 84436 and 84479], so the lab has to emphasize physician education to minimize denials for these charges," Liles says.

"When these codes are reported together, the source of denials is the CCI edits, which prohibit reporting 84439 with 84436 or 84479, ostensibly because they provide similar information," Dettwyler says. CCI edit pairs are used by Medicare and many private insurers to detect codes that should not be paid together for the same patient on the same day, generally because they represent services that are considered "bundled."

"Because these two thyroid-code bundles show a '0' in the CCI modifier indicator column, coders cannot override these edit pairs even though they may override many other CCI edit pairs by using modifier -59 (Distinct procedural service) to indicate that the codes represent two services that are independent from each other," he says.