Frequency, determinants and costs of thyroid function testing in a laboratory serving a large population.

Population-level thyroid function testing is a common clinical practice, yet its rationale and frequency remain understudied. Prior research has shown that thyroid dysfunction is associated with various symptoms, but the relationship between serum thyrotropin (TSH) levels and these symptoms is not well established. Existing knowledge suggests that TSH levels vary with age, sex, and time of day. However, it was already known that these variations do not always correlate with clinical symptoms. That uncertainty drove the need to assess how frequently thyroid testing occurs and how external factors influence TSH levels. No prior work had resolved the extent to which non-pathological variables affect TSH results. This gap motivated an analysis of a large population dataset to better understand testing patterns and TSH variability. The study aimed to identify whether TSH testing is used effectively or if it is overutilized in certain groups. It was already known that older individuals and women are more likely to undergo thyroid testing. This gap motivated an investigation into the factors influencing TSH levels and the clinical utility of the test.

The study aimed to evaluate the frequency and rationale for thyroid function testing in a large population and to determine factors influencing serum TSH levels. The researchers focused on identifying how often thyroid testing occurs and whether it correlates with symptoms of dysfunction. They sought to assess whether TSH testing is overused in certain demographics. The motivation came from the observation that thyroid testing is frequent but may not always be clinically justified. The study aimed to explore whether TSH levels are influenced by non-pathological variables like age, sex, and time of day. It was already known that TSH levels vary with these factors, but the extent of their impact remained unclear. The researchers aimed to determine whether recalibrating TSH reference ranges could improve clinical decision-making. The study also aimed to evaluate the cost implications of widespread thyroid testing.

The study analyzed serum TSH data from a hospital laboratory serving a population of 604,000 in 2018. Researchers excluded patients on medications or with conditions affecting thyroid function to avoid confounding variables. They evaluated the frequency of thyroid testing by age and sex. Ordinary least square regression was used to assess the relationship between TSH levels and potential predictors. The analysis allowed for non-linear relationships between variables. Researchers examined how TSH levels varied with age, sex, time of day, and season. They compared TSH levels across different demographic groups to identify patterns. The study also evaluated the cost implications of current testing practices.

Twenty-eight percent of the population had thyroid function testing in 2018, with notable differences by sex and age. Women had a higher testing rate (28.2%) than men (23.4%). Less than 2% of individuals under 16 years old were tested, while more than 50% of those over 80 years old were tested. Most common symptoms of thyroid dysfunction were not elevated in those with abnormal TSH levels. TSH levels increased with age, particularly after 60 years. Women had higher TSH levels by 0.1 mIU/L on average. TSH levels were higher in the early morning and in winter and spring seasons. The study found that recalculating TSH reference ranges could reduce subclinical dysfunction diagnoses and save costs.

The study found that thyroid function testing is frequently performed in the population, but it does not reliably distinguish individuals with symptoms of thyroid dysfunction. The researchers propose that TSH levels are influenced by age, sex, time of day, and season. These findings suggest that current TSH reference ranges may not be optimal for all groups. Recalculating reference intervals based on these variables could improve diagnostic accuracy. The authors suggest that adjusting reference ranges could reduce unnecessary testing and improve patient care. The study highlights that TSH testing is not always a reliable indicator of thyroid dysfunction. The researchers propose that considering these factors in clinical practice could lead to better resource utilization. Adjusting TSH reference ranges could lead to meaningful cost savings and more accurate diagnoses.