Variability in thyroid function test requests across general practices in south-west England.

BACKGROUND

The number of thyroid function tests (TFTs) performed in the UK and other countries has increased considerably in recent years. Inconsistent clinical practice associated with inappropriate requests for tests is thought to be an important cause for this increase.

AIM

To study the extent of variability in requests for TFTs from general practices.

METHODS

We analysed routine data on all TFTs on patients aged 16 years and over carried out by two hospitals in south-west England (Royal Cornwall Hospital and Royal Devon & Exeter Hospital) during 2010 at the request of 107 general practices.

RESULTS

A total of 195 309 TFT requests were made for 148 412 patients (63% female). The total requests included 192 108 tests for thyroid-stimulating hormone (TSH), 43 069 for free thyroxine (FT4) and 1972 for free tri-iodothyronine (FT3). The number of TSH tests per 1000 list size varied widely across the practices, ranging from 84 to 482. Most of the variation was due to heterogeneity across practices and only 24% of this was accounted for by prevalence of hypothyroidism and socio-economic deprivation.

CONCLUSIONS

There is wide variation in TFT requests from general practice and scope to reduce both unnecessary TFTs and the variability in the clinical practice. Further studies are required to understand the causes for the variability in testing thyroid function.