The impact of thyroid hormone levels and APACHE II scores on the clinical outcome in critically ill patients

Background & objective: Thyroid hormone levels are often raised during stress and acute illness. APACHE II score has been linked to adverse outcome after severe disease. We analyzed the impact of the level of free triiodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormones (TSH), and APACHE II scores on the outcome of critically ill patients admitted to Intensive Care Unit (ICU). Methodology: A cohort prospective study was conducted on critically ill patients in the ICU. Patients' baseline data, thyroid hormone levels, including fT3, fT4, TSH, and APACHE II score within 24 h of admission were compared between 30-day survivors and non-survivors. Multivariate Cox proportional hazards regression analysis was conducted to assess the risk factors for mortality. fT3Non-survivors were significantly older than survivors (55.81 ± 12.61 vs 41.40 ± 11.40, P = 0.003). The APACHE II score was higher in non-survivors (25.88 ± 9.28 vs 22.13 ± 10.42, P = 0.299). Thyroid hormone levels showed no significant difference between the two groups. The area under the receiver-operating curve for APACHE II was 0.610 (0.403-0.818), and for fT3 was 0.523 (0.311-0.735). Conclusion: Although there was no significant difference in thyroid hormone levels between the survivors and non-survivors, the results of this study show that low fT3 levels and high APACHE II scores had a more significant association with adverse clinical outcomes in critically ill patients.