In contrast, the low specificity of this biomarker and the modest correlations with AS grading, with coefficients ranging between 0.30 and 0.60, similar to those found in previous studies [42,43,44], suggest that factors other than AS severity may also affect NT-proBNP levels, and thus this biomarker should be used with caution. The gene discussed is NPPB; the disease is aortic stenosis.