An Estimation of the Incidence of Thyroiditis Among Girls in Primary Care in Spain
Elisa Martín-Merino1, Aida Moreno-Juste2, Belén Castillo Cano1, Mar Martín Pérez1, Dolores Montero Corominas11Spanish Agency for Medicines and Medical Devices (AEMPS), Department of Medicines for Human Use, Pharmacoepidemiology and Pharmacovigilance Unit, Madrid, Spain2Servicio Aragonés de Salud (SALUD); EpiChron Research Group, Aragon Health Sciences Institute (IACS), IIS Aragón; Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC), Zaragoza, Spain
Objective: As for other auto-immune processes, thyroiditis is monitored after vaccinations. The aim was to estimate the baseline incidence of thyroiditis among girls, before investigating papillomavirus vaccination as a potential risk factor.
Methods: Observational cohort study including girls aged 9-18 years and registered between 2002-2016 in the Spanish Primary Care Database for Pharmacoepidemiological Research. Girls were followed until a thyroiditis occurred, 19 years of age, left the cohort, died, or the study ended. Anonymized records were reviewed for diagnosis confirmation (endocrine discharge letter and/or free-text comments) in a random sample. Incidence rate (IR) per 105 person years (/105 py) was estimated.
Results: The cohort numbered 480,169 girls, of whom 641 had a record of thyroiditis: 346 autoimmune thyroiditis; 17 thyroiditis of other types; and 278 unspecified. Incidence of recorded thyroiditis increased with age, from 23.96 at age 9 years to 47.91 at age 14 years, and stabilized around 31.06-34.43 among girls aged 15-18 years. Of the 98 records reviewed, 60.2% were ‘confirmed’ cases, 32.7% ‘possible’ and 7.1% were discarded. After correction for discarded cases, IR=20.83 ‘confirmed’ cases, increasing to 32.12/105 py when ‘confirmed’ plus ‘possible’ cases were included. Between 2002-2005, incidences were lower (16.28 and 20.93 cases/105 py) than in the period 2007-2016 (21.17 and 33.78 cases/105 py) for ‘confirmed’ and ‘confirmed’ plus ‘possible’, respectively.
Conclusion: Two-thirds of the recorded thyroiditis included confirmatory evidence. The incidence of thyroiditis among girls increased with age and in the later period, and remained stable among girls aged 15-18 years.
Manuscript Language: English
