[Impact of retinol-binding protein changes on tafamidis treatment response in patients with transthyretin cardiac amyloidosis].

<b>Objective:</b> To explore the relationship between retinol-binding protein (RBP) levels and disease severity in patients with transthyretin cardiac amyloidosis (ATTR-CA), as well as its impact on therapeutic response to tafamidis. <b>Methods:</b> This retrospective study utilized data from the China National Rare Disease Registry System and included ATTR-CA patients treated with tafamidis between January 2018 and September 2022. Patients were stratified into two groups based on baseline RBP levels: the normal RBP group (≥36 mg/L) and the reduced RBP group (<36 mg/L). Baseline characteristics and clinical data after one year of treatment were collected and compared between the groups. Within the reduced RBP group, patients were further subclassified by changes in RBP levels after treatment (ΔRBP=post-treatment RBP-baseline RBP) into ΔRBP>0 and ΔRBP<0 subgroups. Worsening of global longitudinal strain (GLS) after treatment was defined as the primary outcome, logistic regression analysis was used to identify risk factors influencing therapeutic response to tafamidis in ATTR-CA patients. <b>Results:</b> A total of 52 ATTR-CA patients were included (aged (58.5±12.0) years, 46 males (88%)). Among 39 patients who completed one-year tafamidis treatment, no statistically significant difference was observed in RBP levels post-treatment versus baseline ((27.0±14.3) mg/L vs. (25.9±15.4) mg/L, <i>P</i>=0.261). Compared to the normal RBP group, the reduced RBP group had significantly higher estimated glomerular filtration rate-adjusted N-terminal pro-B-type natriuretic peptide levels (2 316.0 (1 161.5, 6 027.8) ng/L vs. 806.2 (349.5, 1 735.8) ng/L), higher left ventricular mass index ((164.4±46.5) g/m² vs. (123.9±31.8) g/m²), and lower left ventricular ejection fraction ((50.8±11.3)% vs. (58.8±6.2)%) (all <i>P</i><0.05). Among 31 patients in the reduced RBP group who completed one-year tafamidis treatment, 23 were classified as ΔRBP>0 and 8 as ΔRBP<0. The ΔRBP<0 group exhibited greater GLS worsening than the ΔRBP>0 group (0.7 (-0.1, 1.4)% vs. -0.4 (-1.4, 0.2)%, <i>P</i>=0.027). Multivariate logistic regression analysis revealed that ΔRBP<0 was an independent risk factor for GLS worsening (<i>OR</i>=8.584, <i>95%CI</i> 1.186-62.150, <i>P</i>=0.033) in ATTR-CA patients. <b>Conclusion:</b> ATTR-CA patients with reduced RBP levels exhibit more severe left ventricular structural and functional impairment compared to those with normal RBP levels. Decline in RBP during treatment (ΔRBP<0) is associated with poorer response to tafamidis treatment. Monitoring RBP dynamics may assist clinicians in assessing disease severity and therapeutic response in ATTR-CA patients.