Are GPs using TSH indiscriminately

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Are GPs using TSH indiscriminately?
WAIKATO CLINICAL SCHOOL Te Kura Rata O Waikato

• Gibbons V, Conaglen J, Lillis S, Lawrenson R.

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Aim

• To ascertain the use of thyroid function tests by
  general practitioners
• To identify the incidence of thyroid disease
• To draw conclusions as to the appropriateness of
  testing undertaken by general practitioners

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Background

• Thyroid dysfunction is common
• Presenting features of overt disease are known
  while symptoms of early thyroid disease can be
  subtle
• GPs say they order tests based on signs and
  symptoms

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Hypothyroidism

• Stiffness
• Coronary Artery Disease
• Raised cholesterol
• Carpal tunnel syndrome
• Voice changes
• Slower pulse
• Hearing loss
• Heart disease

• Raised TSH with low FT3 and FT4
• Five times more common in women
• Slow onset of symptoms
• Weight gain
• Cold intolerance
• Lack of energy
• Hypertension
• Constipation
• Skin, hair changes

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Hyperthyroidism

• Weight loss
• Heat intolerance
• Anxiety Irritability
• Increased heart rate
• Atrial Fibrillation
• Heart disease
• Increased sweating
• Muscle weakness
• Tremor
• Skin changes

• Hair loss
• Abnormal menses
• Goitre
• Exopthalmos
• Osteoporosis

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Methods

• 2 large urban New Zealand General Practices with
  a registered population of 21,461 18 years of
  age
• TFTs were taken over a 12 months period from
  laboratory data
• Data linked to patient records held in general
  practice
• Outcomes analysed by age and gender

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1 in 5 registered patients will have a TSH in a
12 month period
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90 of TSH results are normal
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9.6 of sample population have abnormal thyroid
function
Incidence of hyperthyroidism 4.7/1000 Incidence
of hypothyroidism 2.2/1000
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Findings similar to population-based screening
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Is TSH being used as a screening test?

• Current use of signs and symptoms to identify
  cases are no more able to discriminate cases than
  population screening
• 1/5th of adults (2/5ths over 65yrs) are tested in
  a 12 month period
• Equivalent to opportunistic screening

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Should we use FT4/FT3 as well as TSH?

• Use FT4/FT3 if TSH is elevated
• Order FT4/FT3 if barn door signs and symptoms
• Endocrinologists argue for FT4/FT3 in addition to
  TSH to avoid missing cases of hypopituitarism.

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GPs use of tax-payer money!

• Total Lab cost for TSH equal to 30,565 cost of
  FT4 tests (8636) for one year in patients
  without known thyroid dysfunction
• Cost per case 1568 (20F1088, 5M1829)
• Cost effectiveness improves when patients get
  older and is more favourable in women

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Endocrinologists use of tax-payer money!

• Cost to find one case of hypopituitarism
• 347,619

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Discussion

• Screening for thyroid dysfunction is currently
  not recommended
• Case-finding approach does not discriminate
  patients with disease
• Use of TSH as an opportunistic screening test is
  cost-effective
• What do we do about subclinical disease?

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Conclusions

• Most thyroid dysfunction is subclinical
• General practitioners should use opportunistic
  screening with TSH to find new cases of thyroid
  dysfunction
• Such a strategy is cost-effective
• The routine addition of FT4 to screen for thyroid
  dysfunction is less attractive