REassessing the diagnostic Strategy for clinically relevant Thyroid disorders in Older patients in primary caRE; RESTORE

In general practice, older patients often present with non-specific symptoms, including fatigue, and general malaise. Since these non-specific symptoms might indicate a thyroid disorder, general practitioners (GPs) frequently test for thyroid disorders in these patients. With the current GP diagnostic strategy for thyroid disorders (first TSH, if TSH is abnormal automatically assess FT4), subclinical thyroid disorders are often found. The clinical relevance of subclinical thyroid disorders in older GP patients is limited, but these abnormal tests results may do unnecessarily alarm patients, could lead to unnecessary lab analyses, unnecessary treatment for selected patients and unnecessary use of resources. In addition, from July 2020 onwards patients will gradually have direct access to their electronic patient records, including GP-records. Patients will likely be confronted with and potentially unnecessarily alarmed by these abnormal TSH results, while diagnostics or treatment may clinically not be necessary. This highlights the need for a new diagnostic strategy. This project aims to assess the diagnostic value of two new diagnostic testing strategies to identify the least clinically irrelevant abnormal thyroid function test results without missing clinically relevant thyroid disorders that require clinical action (treatment, additional diagnostic tests or follow-up measurements) in GP patients aged 60 years and over. In WP1 (work package), we will collect new data, including information on medical history, complaints and medication use from 2000 older GP patients. We will then model the performance of new laboratory testing strategies to identify the least clinically irrelevant abnormal thyroid function test results without missing clinically relevant thyroid disorders in older GP patients, based on 1) widening the TSH reference range for measuring FT4 and 2) measuring FT4 first instead of TSH first. In WP2, we will model the same new laboratory testing strategies in a large Dutch population based study to compare with the results from WP1 for persons aged 60 years and over to compare with the results of WP1. We will also model the diagnostic testing strategies in those aged 18-59 years. In WP3, the performance of the three diagnostic testing strategies (the current strategy and the two new strategies) will be discussed with experts, including older persons and patients with thyroid disease, GPs and medical specialists in a Delphi procedure. The aim of WP3 is to prioritize the testing strategies including the weighing of the risks and benefits of the testing strategies and potential application of the new strategies for individuals aged 60 years and over and those aged 18-59 years. In addition, barriers and facilitators for implementation of the new promising strategies will be discussed. With these 3 work packages, this project will lead to an optimized evidence-based diagnostic strategy that identifies the least thyroid function test results that are considered as clinically irrelevant, in order to minimize unnecessary alarming patients, and/or initiation of unnecessary additional tests, treatment or follow-up and still identifies GP patients with clinically relevant thyroid disorders. This is an important step in personalized diagnostics and medical care for older GP patients.