Serum total triiodothyronine (T3) as a predictor of mortality and morbidity in critically ill patients and its correlation of predictability with acute physiology and chronic health evaluation II score: A prospective observational study

Background: The aim is to assess the prognostic value of total T3, total T4, and thyroid-stimulating hormone among critically ill patients admitted to the medical intensive care unit (ICU) in association with mortality and its correlation with the acute physiology and chronic health evaluation II (APACHE II) score.

METHODS: : Our prospective observational study consists of 257 patients without known thyroid diseases admitted to the medical ICU. The baseline characteristics of the patients were recorded, including the APACHE II score and thyroid hormone levels at ICU admission. Based on the primary outcome of mortality, we analyzed the data by appropriate statistical methods. A P < 0.05 was considered significant.

Results: Of the 257 patients included in the study, 47 (18.28%) succumbed to their illnesses. A significant difference in T3 levels (P < 0.001), T4 levels (P < 0.001), and APACHE II score (P < 0.001) was found between the survivors and the nonsurvivors. There was negative correlation observed between T3 and APACHE II score (r = -0.448, P < 0.001) and T4 and APACHE II score (r = -0.221, P ≤ 0.001). Multivariate logistic regression analysis determined T3 to be the only independent predictor of ICU mortality among thyroid hormones. The area under the curve (AUC) for T3 (0.811 ± 0.04) was almost equal to that of the APACHE II score (0.858 ± 0.029). The duration of ICU stay and hospital stay in patients with low T3 was significantly higher compared to patients with normal T3.

Conclusion: Serum T3 is a good indicator for predicting mortality and morbidity among critically ill patients.