Prognostic significance of nonthyroidal illness syndrome in critically ill adult patients with sepsis.

Aim: This study was performed to investigate the association of non-thyroidal illness syndrome (NTIS) with 28-day mortality in adults with sepsis.

Methods: We performed a prospective observational analysis of adult patients with sepsis. Patients' demographic data, comorbidities, the blood test results including thyroid hormone analysis at admission, Acute Physiologic and Chronic Health Evaluation II score and Sequential Organ Failure Assessment score were compared between 28-day survivors and non-survivors. Further patients were divided into 3 groups; non-NTIS, NTIS group A (low total tri-iodothyronine (T3) and NTIS group B (low T3 with low thyroxine (T4). Multivariate Cox proportional hazards regression analysis was performed to determine the risk factors for mortality.

Results: A total of 360 patients were included, and overall mortality was 30%. The mortality of non-NTIS patients was 13.4%; group A, 50.1%, and group B 69.1% ( P < .001). The median T3 (IQR) in non-survivors and survivors was 0.74 (0.56-1.17) and1.58 (0.91-2.13) and median free T3 (IQR) 2.40 (1.13-3.01) and 4.03 (3.03-7.13) respectively ( P < .001). In Cox proportional hazards analysis, NTIS group A (hazard ratio, 1.66; 95% confidence interval [CI], 1.00-2.76) and group B (hazard ratio, 2.57; 95% CI, 1.53-4.34). The area under the receiver-operating curve of NTIS groups was 0.68 (95% CI, 0.63-0.72).

Conclusion: The T3 and free T3 were significantly lower in non-survivors compared with that in survivors and that a combination of low T3 with low T4 was associated with greater mortality than low T3 alone. A lower free T3 is independently associated with 28-day mortality.