Prevalence of Thyroid Dysfunction in Hamilton General Practice

1
Prevalence of Thyroid Dysfunction in Hamilton
General Practice

• Veronique Gibbons, Vignesh Naras, Dr. Steven
  Lillis, Dr. John Conaglen, Prof. Ross Lawrenson

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Why are we interested?

• Overt or subclinical thyroid dysfunction common
  within the community
• International data estimates prevalence of
  thyroid dysfunction between 1.0-9.2 (Canaris et
  al., 2000 Sawin et al., 1985)
• Limited prevalence data on New Zealand population
• Can international data be extended to the New
  Zealand population?
• Population structure
• Ethnic variations
• Dietary iodine intake

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Iodine fortification

• Future mandatory fortification of iodine in food
• Iodised salt in breads, cereals, biscuits
• Re-emergence of mild-moderate iodine deficiency
  in New Zealand and parts of Australia over past
  10-15 years
• Iodine deficiency leads to increase in thyroid
  volume, i.e. goitre

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Aim

• Among adults over 18 years, in the general
  practice setting
• Establish prevalence and incidence of thyroid
  dysfunction
• Compare to international findings
• Explore the use of TFTs in General Practice

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Our thyroid study in Hamilton

• Cross-sectional review
• Took place between Nov 2006 Jan 2007. Summer
  studentship for 10 weeks.
• 2 Hamilton general practices
• Total patients registered over 18 yrs 21,290.

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Methods

• Stage 1 Identified patients through codes and
  medications
• Stage 2 confirmed their thyroid status
• Stage 3 matched to lab data

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Results case finding

• Stage 1 672 patients were identified by code or
  medication
• Stage 2 644 were confirmed with thyroid
  dysfunction from notes.
• Reasons for non inclusion
• - 6 no notes
• - 10 euthyroid (treated and not on medication)
• - 3 psychiatric (no evidence of TD)
• - 4 thyroiditis (now resolved)
• - 5 wrong diagnosis
• Stage 3 18 patients identified from lab data
• FINAL TOTAL 662 /21290 3.1

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Results by category
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Prevalence by age and gender
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Prevalence by ethnicity
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Incidence
12
Laboratory tests
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Laboratory Requests

• Recommendation for TSH alone as a first line test
• Ratio of tests TSH FT4
• Study 600621592.81
• Waikato 59642 25191 2.41
• Normal TSH
• Study 90.8, not without known TD 96
• Waikato (2006) 96

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Conclusions

• This was a pilot to inform further studies
• Cannot generalise findings regarding prevalence
  among Maori
• Maori study population 7 vs Hamilton Maori
  population 14
• Need for investigation of thyroid dysfunction in
  an area with a representative Maori population

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Future implications

• To establish likelihood of a positive test result
  depending on patients age, gender (and
  ethnicity).
• To establish current incidence and prevalence
  prior to fortification of food with iodine
• To establish current use of TFT to enable
  comparison to any future performance measure
• To develop guidelines for general practice