Endocrine Abstracts

Behavior of thyroid function tests in a Brazilian elderly population using Big Data

Introduction: Interpretation of thyroid function data has changed over the last decades with several groups demonstrating changing in the thyroid axis with aging, particularly with a progressive increase in age-related TSH. With the proliferation of studies with large datasets, termed Big Data, sample sizes are no longer a challenge, and the possibility of using clinical laboratory databases to evaluate this population becomes a practical and innovative solution.ObjetiveThe aim of the present study is to determine the behavior of TSH and free T4 (fT4) levels (in two different methods) for a population over 60 years old using the database of thyroid function tests from Fleury Laboratory in Brazil.

Methods: Data from 8.694.807 blood samples were retrospectively analyzed and filtered first for the TSH analysis using concentration within the reference values of free T4 (fT4), negative anti-thyroid antibodies and the absence of medication use. Thereafter, the same sample was analyzed for two different methods of fT4 (fT4a-Roche Diagnostic and fT4b-Beckman Coulter). The statistical analyzes were performed using R software. Wilcoxon / Kruskal-Wallis test was used to compare concentrations of TSH among two age groups, from 18 to 59 years old (under-60), and over 60 up to 107 years old (over-60). For the FT4 analysis, reference values for each group in each method were obtained through bootstrapping. Results From the initial group, 42.477 TSH samples were selected to be studied. TSH levels was similar in both sexes, but with noticeably difference between the age-groups increasing with age in the 95^th upper limit: 6.86 (60-69 years), 7.92 (70-79) and 10.46 mUI/l (over 80 years). For fT4a, 10.038 samples and for fT4b, 658.267 samples were analyzed, and an increase in the levels of fT4 were observed between the age groups, raising from 1.5 ng/dL in the group 18-59 years-old to 1.82 ng/dL in the group over 80 years old for fT4a and from 1.0 ng/dL to 1.4 ng/dL for fT4b for the same age groups.

Conclusions: Increase of both TSH and fT4 with age is well documented in literature and this large database analyzed through big data techniques was able to identifies the same phenomenon in the Brazilian population. This data could be helpful to determine age specific thyroid function tests values that will improve diagnosis of thyroid disease in elderly patients and possibly avoid overdiagnosis of subclinical hypothyroidism in this population.