title: Thyroid function testing in primary care: overused and under-evidenced? A study examining which clinical features correspond to an abnormal thyroid function result.
abstract: OBJECTIVE
  Diagnostic testing is increasing in primary care, including for thyroid disease. This study examined which clinical features were associated with an abnormal thyroid stimulating hormone (TSH) result.
  
  
  METHODS
  This was a cross-sectional study in one general practice of 16,487 patients in Exeter, Devon, UK.
  
  
  METHODS
  We examined the primary care records relating to every TSH test taken in the year from August 2012, and extracted symptoms and/or the indication for testing. Associations with an abnormal result were tested using multivariable logistic regression. A cohort study was then performed of 100 patients newly recorded with each of the six features associated with an abnormal test result in the cross-sectional study, and the proportions tested for TSH and the results of that testing identified.
  
  
  RESULTS
  Two thousand thirty-five patients (12% of the practice population) had TSH testing in the year. Of these 35 (1.7%) had a TSH >4.5 mIU/l, suggesting hypothyroidism, and 7 (0.3%) had TSH <0.01 mIu/l suggesting hyperthyroidism. Features associated with an abnormal TSH were: pregnancy, odds ratio 41 (95% confidence interval 9.3-180), constipation 9.7 (2.1-45), palpitations 23 (3.4-150), hair loss, 21 (2.0-230), weight gain, 18 (1.6-190) and diarrhoea, 13 (1.2-130); in separate analyses only pregnancy and constipation were associated with a raised TSH, and the remaining four features with a low TSH.
  
  
  CONCLUSIONS
  The diagnostic yield of thyroid disease in this study was 2.1% suggests testing could be better targeted without missing diagnoses. The symptoms associated with thyroid disease differ from those generally reported. This may represent fewer patients presenting with advanced disease.
authors.affiliation: Primary Care Diagnostics, Exeter University and awerhun@nhs.net.
authors.forename: Alexander
authors.initials: A
authors.lastname: Werhun
authors.affiliation: Peninsula College of Medicine and Dentistry, Exeter, UK.
authors.forename: William
authors.initials: W
authors.lastname: Hamilton
mesh_terms: D015331:Cohort Studies; D003248:Constipation / Q000097:blood; D003430:Cross-Sectional Studies; D003967:Diarrhea / Q000097:blood; D005260:Female; D006201:Hair Diseases / Q000097:blood; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000175:diagnosis*; D007037:Hypothyroidism / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D018579:Patient Selection; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood*; D011320:Primary Health Care / Q000706:statistics & numerical data*; D013960:Thyroid Function Tests / Q000706:statistics & numerical data*; D013972:Thyrotropin / Q000097:blood*; D015430:Weight Gain
chemical_list: D013972:Thyrotropin
keywords: Diagnostic tests; endocrinology disorders (thyroid); family health; screening; thyroid disorders.