Is serum transthyretin a reliable marker of nutritional status in patients with end-stage renal disease?

Objective To test the value of serum transthyretin (TTR) concentration as a nutritional marker in renal patients. Methods The study included 115 renal patients, out of which 35 are on conservative treatment, 50 on hemodialysis and 30 renal transplant recipients, and 31 healthy control subjects. Serum TTR, albumin, transferrin, C-reactive protein (CRP) and α1 anti trypsine (AAT) were assessed by immunoturbidimetry, and vitamin A by HPLC. Linear regression models were applied to test the association between serum TTR and body mass index (BMI). Results Serum TTR concentrations were normal, but serum vitamin A, CRP and AAT concentrations were significantly higher in patients. In renal patients, serum TTR was positively and independently related to BMI and was significantly lower in malnourished than well-nourished patients (367 ± 91 vs. 417 ± 130 mg/L; p = 0.05). The risk of serum TTR < 300 mg/L was higher in malnourished patients [OR, 4.82 (1.78–13.2); p = 0.001]. Conclusion Serum TTR concentrations were at normal range in renal patients despite evidence of malnutrition and inflammation. However, they were related to BMI and were significantly lowered in malnourished patients. Thus, serum TTR would reflect nutritional status in renal patients. However, the cutoff of malnutrition should be raised to 300 mg/L.