Pathology/Lab Coding Alert

Question: The physician ordered a TSH test with the diagnosis "decreased TSH." How should we code this?

Answer: The correct code for the lab test is 84443 (Thyroid stimulating hormone [TSH]). The best ICD-9 code for the narrative diagnosis of "decreased TSH" is 259.9 (Unspecified endocrine disorder).

Although you should avoid "unspecified" ICD-9 codes if you have a more definitive diagnosis, you don't have much choice based on the information the physician provided. Physicians may order one of several thyroid tests such as TSH for a broad range of symptoms or ill-defined conditions such as constipation (564.0x) or abnormal weight gain (783.1), but you don't mention that the physician describes any such symptoms.

Similarly, you can't apply a specific diagnosis that the physician doesn't provide, such as hypothyroidism (244.9, Unspecified acquired hypothyroidism) or even 246.9 (Unspecified disorder of thyroid).

Here's why: Disorders other than a thyroid condition can account for low TSH, such as a pituitary disorder (253.x, Disorders of the pituitary gland and its hypothalamic control). That's why the most specific diagnosis code you can use is 259.9.