Do general practitioners use thyroid stimulating hormone assay for opportunistic screening?

Abstract

Aim: The presenting features of early thyroid disease can be subtle and non-specific; consequently, general practitioners (GPs) have a low threshold for ordering thyroid function tests (TFTs). This study examined the use and results of TFTs by GPs in a 1-year period in a population-based sample of adults without known thyroid disease enrolled in general practice.

Method: This record linkage study analysed the use of TFTs over a 12-month period from laboratory data, which were linked to patient's GP records from two large urban New Zealand general practices with a total registered population of 21,290 patients. Outcomes were analysed by age and gender.

Results: One in six adult patients visiting their GP in a 12-month period had a thyroid stimulating hormone (TSH) test, whilst only 1 in 20 had a free thyroxine (FT4) test. 7.0% had an elevated TSH concentration and 1.0% had a low TSH concentration, most with subclinical disease. Rate of testing was higher in females compared with males.

Conclusion: This study suggests that general practitioners are opportunistically screening with TSH alone to find new cases of thyroid disease.