Validation of two simple scores to identify increased risk of transthyretin amyloid cardiomyopathy in heart failure with preserved ejection fraction

Abstract Background Transthyretin Amyloid Cardiomyopathy (ATTR-CM) is an emerging underdiagnosed cause of heart failure (HF). 99mTc-3, 3-diphosphono-1,2-propanodicarboxylic acid (DPD) allows ATTR-CM diagnosis in the absence of histology. Recently two simple clinical scores to identify increased risk of ATTR-CM in patients with heart failure and preserved left ventricular ejection fraction have been developed and validated. Purpose To assess the prevalence of ATTR-CM in a Mediterranean cohort of patients at risk, and to externally validate the Mayo ATTR-CM and T-Amylo scores. We also explore its diagnostic accuracy improvement by adding N-terminal pro-B-type natriuretic peptide (NT-proBNP). Methods Retrospective cohort study of consecutive patients with suspected cardiac amyloidosis referred to DPD between March 2017 and November 2020. Scans were reported using a visual grading system (0 to 3 increasingly; 2-3 positive) on planar images. Patients with clonal dyscrasia or those without rule-out tests (serum free light chain assay, and serum and urine protein electrophoresis with immunofixation) were excluded. Discrimination was obtained using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve based on the ATTR-CM score [High risk: score ≥ 6. Components: age (60-69 = 2 points; 70-79 = 3 points; ≥80 = 4 points), male sex = 2 points, hypertension = -1 point, ejection fraction <60% = 1 point, posterior wall thickness ≥12 mm = 1 point, relative wall thickness (septal + posterior wall thickness/left ventricular end diastolic diameter) >0.57 = 2 points], and T-amylo score [High risk: score > 6. Components: age ≥ 80 years = 1 point, interventricular septum thickness ≥16 mm = 2 points, low QRS interval voltage = 2 points, male gender = 3 points, and carpal tunnel syndrome = 3 points. Calibration was assessed with the Hosmer-Lemeshow goodness-of-fit test. Results A total of 200 patients were included with a mean age of 78.5 ± 11 years, 45.5% male, left ventricular ejection fraction 58% ± 12 and a median NT-proBNP of 2310 pg/mL (Table 1). 81 (40.5%) and 10 (5.0%) patients were categorized as a high-risk group due to ATTR-CM score value ≥6 and simplified T-Amylo score >6, respectively. Prevalence of ATTR-CM was 17.5%. The AUC for the Mayo ATTR-CM and T-Amylo scores in our cohort were 0.83 (95% CI 0.75-0.90) and 0.79 (95% CI 0.69-0.88) respectively, with an appropriated calibration (Figure 1). The addition of NT-proBNP to the scores did not increase the AUC (p=0.19 and p=0.08), with a Net Reclassification Improvement (NRI) of 0.055 (95% CI - 0.110 to 0.206) and 0.033 (95% CI - 0.113 to 0.224) respectively. Conclusion These two simple clinical scores are valid and reliable tools for ATTR-CM diagnosis in our Mediterranean cohort. Added to clinical suspicion, can improve the diagnostic workup for ATTR-CM, irrespective of NT-proBNP values.