Pathology/Lab Coding Alert

Ensure medical necessity for coverage.

If your lab performs blood tests for thyroid function, you need to stay up to date on coverage rules if you don’t want to get stuck holding the bag for the tests’ costs.

Thyroid-test coding is complex because physicians may order the assays for a host of reasons, and because labs must abide by CMS’s national coverage determination (NCD) and CCI edits, which provide nuanced coverage rules. Read on to make sure you have all the tools you need to file clean claims for thyroid testing.

Know Medical Necessity Indicators

Physicians order thyroid function tests to help evaluate the under- or over-production of thyroid hormone(s). “The test results can help physicians reach a diagnosis and devise and monitor treatment,” explains William Dettwyler, MT AMT, president of Codus Medicus, a laboratory coding consulting firm in Salem, Ore.

Medicare and many third-party payers consider thyroid testing medically reasonable and necessary for the following purposes:

• to confirm or rule out primary hypothyroidism or hyperthyroidism
• to distinguish between primary and secondary hypothyroidism
• to monitor progression of disease and therapy in patients with thyroid dysfunction
• to monitor thyroid hormone levels in patients on long-term thyroid drug therapy
• to monitor thyroid hormone levels associated with conditions such as goiter, thyroid nodules, thyroid or other endocrine gland neoplasms, or history of such neoplasms.

Other conditions that may indicate medical necessity for thyroid function testing include the following:

• metabolic disorders
• malnutrition
• hyperlipidemia
• certain types of anemia
• psychosis and non-psychotic personality disorders
• unexplained depression
• ophthalmologic disorders
• various cardiac arrhythmias
• menstruation disorders
• certain skin conditions
• vague symptoms such as myalgia, malaise, hypothermia, alterations of consciousness, as well as various signs in the nervous, musculoskeletal, integumentary, cardiovascular, and gastrointestinal systems.

You’ll find a comprehensive list of ICD-10-CM codes describing conditions that show medical necessity for thyroid testing in the thyroid testing NCD. For instance, the list includes the following, and many, many more codes:

• C73 (Malignant neoplasm of thyroid gland)
• D51.0 (Vitamin B12 deficiency anemia due to intrinsic factor deficiency)
• E03.9 (Hypothyroidism, unspecified)
• E04.0 (Nontoxic diffuse goiter)
• E78.4 (Other hyperlipidemia)
• F23 (Brief psychotic disorder)
• I48.1 (Persistent atrial fibrillation)
• L63.9 (Alopecia areata, unspecified)
• N91.2 (Amenorrhea, unspecified).

Caution: “Payers don’t usually cover thyroid function for screening, so you should always report the most specific diagnosis that the ordering physician provides, even if it’s just vague signs and symptoms,” Dettwyler says.

For multiple diagnoses: If the ordering physician lists more than one diagnosis as the reason for the test, you need to decide which code(s) to report, and which to list as the primary diagnosis. If the order identifies a disease process, such as hypothyroidism, you shouldn’t additionally assign codes for signs and symptoms that are routinely associated with hypothyroidism. But if the lab order identifies two codes and “both diagnoses equally meet the criteria for primary diagnosis, either option will work,” explains Kimberly Quinlan, CPC, senior medical records coder in New York’s University of Rochester Medical Center.

Understand Lab Methods

The lab tests considered in the thyroid testing NCD include the following:

• 84436 (Thyroxine; total) often ordered as T4 or TT4
• 84439 (Thyroxine; free) often ordered as FT4, Free T4, or FTI
• 84443 (Thyroid stimulating hormone (TSH))
• 84479 (Thyroid hormone (T3 orT4) uptake or thyroid hormone binding ratio (THBR)).

The serum levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4) are instrumental in diagnosing hyperthyroidism or hypothyroidism. After a diagnosis of thyroid dysfunction, clinicians often order further testing 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). Labs used the results to calculate the free thyroxine index (FTI), which provides an indirect proportional estimate of FT4.