Epidemilogy of Thyroid Disease Ross Lawrenson

Prevalence of Thyroid Dysfunction in Hamilton (New Zealand) General Practice Veronique Gibbons, Dr. John Conaglen, Dr. Steven Lillis, Vignesh Naras, Prof. Ross Lawrenson Hamilton, New Zealand • 4th largest city in New Zealand • 15% Maori, 10% Asian population • Serves wide rural hinterland and has a tertiary/base hospital with 600+ beds • 90% patients in the Waikato region/Hamilton are registered with Waikato Primary Health Waikato New Zealand General Practice • 21 District Health Boards which fund 81 Primary Health Organisations (PHOs) • Most general practitioners are contracted to provide services to a PHO. 40% of GP income derived from patient fees, 35% in capitation, 10% from ACC fees and remainder from immunisation, maternity etc. • High use of computers – 3 or 4 main suppliers (80% use Medtech). Use Read codes. • Pathology provided though private laboratories paid a fee per service by the DHB – 2 currently operate in our district. Why are we interested? • Thyroid dysfunction is reported to be common within the community (O’Leary et al, 2006) • Limited prevalence data on New Zealand population • Dietary iodine levels have been falling so proposal to fortify bread/other foods with iodine • Ministry have proposed the use of thyroid function tests be used as a measure of general practice quality Aim • Among adults over 18 years, in the general practice setting: – Establish prevalence and incidence of thyroid dysfunction – Compare to international findings Our thyroid study in Hamilton • Cross-sectional review of computerised records • Took place between Nov 2006 – Jan 2007. Summer studentship for 10 weeks. • Also looked at new cases from Jan –Dec 2006 via records and laboratory data • 2 Hamilton general practices • Total patients registered over 18 yrs = 21,290. Methods • Stage 1: Identified patients through computerised records • Used Read codes and prescription codes • Stage 2: confirmed their thyroid status by review of records • Stage 3: matched to laboratory data 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 in past, not on medication) - 3 psychiatric (no evidence of TD) - 4 thyroiditis (now resolved) - 5 wrong diagnosis • Stage 3: 18 additional patients identified from laboratory data FINAL TOTAL: 662 /21290 = 3.1% Prevalence by Category 2.50% 2.00% 1.50% 1.00% 0.50% 0.00% HYPO HYPER OTHER Prevalence by age and gender 160.0 140.0 120.0 Per 1000 population 100.0 Female Male 80.0 60.0 40.0 20.0 0.0 18-29 30-39 40-49 50-59 Age group 60-69 70-79 80+ Comparing prevalence of overt thyroid dysfunction per 1000 population Study Our study Tunbridge UK QOF Undiagnosed only Chuang Diez Canaris Hollowell (NHANES III) Year Location Number in study % Hyper % Hypo 2006 1977 2007 Hamilton, NZ Whickham, UK 20,290 2779 0.2 1.6% 2.4 1.1% 2.5% 1998 2003 Taiwan Madrid, Spain 917 294 25,862 16,533 0.1 0.1 0.1 0.5 0.8 1 0.4 0.3 2000 Colorado, USA 1990 USA Prevalence by ethnicity 3.00% 2.50% 2.00% 1.50% European Maori 1.00% 0.50% 0.00% Hyper Hypo Other Incidence 8.0 7.0 6.0 per 1000 5.0 4.0 3.0 2.0 1.0 0.0 18-29 30-39 40-49 50-59 Age group Other Hypo Hyper 60-69 70-79 80+ Comparing incidence of hyperthyroidism per 1000 population Study Our study Vanderpump Brownlee Morgensen Year Location Number in study Female overt hyperthyroidism Male overt hyperthyroidism 2006 1995 1990 1980 1984 Hamilton, NZ Great Britain Canterbury, NZ Denmark Great Britain 20,290 2779 372,948 439,764 1,641,949 0.8 0.8 0.41 0.47 0.36 0.2 0.1 0.15 0.1 0.1 Barker Laboratory Requests • Recommendation for TSH alone as a first line test in investigating possible thyroid dysfunction • Ratio of tests TSH: FT4 – Study 6006:2159=2.8:1 – Waikato 59642: 25191= 2.4:1 • Normal TSH – Study 91.8%,without known TD – Waikato (2006) 96% Number of TSH tests per 1000 in 2006 in study practices by age and gender 500.0 450.0 400.0 350.0 300.0 Per 1000 Female Male 250.0 200.0 150.0 100.0 50.0 0.0 18-29 30-39 40-49 50-59 60-69 70-79 80+ Average Age groups Comparison of International Data Canaris et al.2000 (N=25682) Michelangeli et al. 2002 (N=2111) Hamilton 2006 (N=21462) Normal TSH reading Abnormal TSH Elevated TSH Decreased TSH 0.3-5.1mIU/L 0.4-4.0 mIU/L 0.3-5.0 mIU/L 11.7% 9.5% 2.2% 9.2% 6.4% 2.8% 8.2% 7% 1.23% Discussion • Current data on incidence and prevalence of thyroid dysfunction is lacking in New Zealand • This issue arose from a lack of data to assess the impact of proposed food additives legislation • Use of combination of general practice data and laboratory data seems a sensitive way of identifying cases of disease. • Access to full records allows estimate of validity of diagnosis and improves specificity • With an ageing population and greater female longevity, the prevalence of thyroid disease will only increase. Conclusions • This study gives a picture of thyroid dysfunction in the community prior to mandatory fortification of food with iodine. • Prevalence of overt thyroid disease in our populationbased study was 3.1% • Incidence of thyroid dysfunction is 2.0 per 1000 per annum. • This burden is greatest in women and in the older population.