A simple staging system using biomarkers for wild-type transthyretin amyloid cardiomyopathy in Japan

Abstract

Aims: It has been reported that a staging system combining N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T (hs-cTnT) or estimated glomerular filtration rate (eGFR) is useful in patients with wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM). However, these studies were mainly conducted in Western countries, and their usefulness for the Japanese population is unclear. We examined and validated the staging system using hs-cTnT, eGFR, and B-type natriuretic peptide (BNP) in Japanese patients with ATTRwt-CM.

Methods and results: We retrospectively evaluated 176 patients with ATTRwt-CM. The cut-off values of hs-cTnT and eGFR were selected as 0.05 ng/mL and 45 mL/min/1.73 m² , respectively, based on a previous report. The optimal cut-off value of BNP was 255.6 pg/mL to predict all-cause mortality (sensitivity, 75%; specificity, 58%; area under the curve, 0.69; 95% confidence interval [CI], 0.61-0.78; P < 0.001) based on a receiver operating characteristic curve. We defined the cut-off value of BNP as 250 pg/mL. Increased hs-cTnT (>0.05 ng/mL) and BNP (>250 pg/mL) and decreased eGFR (<45 mL/min/1.73 m² ) were significant predictors of poor prognosis (P < 0.05). We calculated the score by adding 1 point if hs-cTnT and BNP levels increased or eGFR decreased by more than the cut-off value. The hazard ratio of all-cause death adjusted by age and sex, using score 0 as a reference, was 0.44 (95% CI 0.08-2.49, P = 0.44) for score 1, 3.69 (95% CI 1.21-11.21, P = 0.02) for score 2, and 5.40 (95% CI 1.57-18.54, P = 0.007) for score 3. We divided patients into a low score group (0-1 point) and high score group (2-3 points). Kaplan-Meier analyses revealed significant differences in all-cause death and rehospitalization for heart failure (log rank test; P < 0.001), and after adjusting for sex and age, the hazard ratio of all-cause death was 6.96 (95% Cl 2.88-16.83, P < 0.001) and that for rehospitalization for heart failure was 4.27 (95% Cl 2.26-8.07, P < 0.001) in the high-risk group, compared with those in the low-risk group. The median survival period was 32.0 months in the high-risk group.

Conclusions: This simple staging system, which combines hs-cTnT, BNP, and eGFR, was useful for predicting prognosis in Japanese patients with ATTRwt-CM. This system can objectively evaluate the disease progression of ATTRwt-CM and may be useful for patient selection for disease-modifying therapy.

Keywords: Amyloid cardiomyopathy; Biomarker; Staging; Transthyretin.