External Validation of the Kumamoto Criteria in Transthyretin Amyloid Cardiomyopathy Screening　― A Retrospective Cohort Study ―

Background: The Kumamoto criteria have been proposed as a non-invasive screen for transthyretin amyloid cardiomyopathy. This study assessed the validity of the Kumamoto criteria externally. Methods and Results: The study included 138 patients (median age 73 years; 65% male) who underwent (99 m)Tc-pyrophosphate (PYP) scintigraphy. Patients were divided into 4 groups according to total scores on the Kumamoto criteria (i.e., 0–3) for the following 3 factors: high-sensitivity cardiac troponin T ≥0.0308 ng/mL, wide (≥120 ms) QRS, and left ventricular posterior wall thickness ≥13.6 mm. The diagnostic performance and positive predictive value (PPV) of the Kumamoto criteria for positive (99 m)Tc-PYP scintigraphy were validated. Eighteen (13%) patients were positive on (99 m)Tc-PYP scintigraphy. The Kumamoto criteria had a favorable diagnostic performance (area under the curve 0.808). The PPV for groups with scores of 0, 1, 2, and 3 was 0% (n=0/42), 11% (n=6/57), 21% (n=7/33), and 83% (n=5/6), respectively, which is lower, particularly for those with a score of 2, than in the original Kumamoto cohort. However, the PPV increased after combining the Kumamoto criteria with a history of orthopedic diseases (spinal canal stenosis and/or carpal tunnel syndrome). Conclusions: This study suggests that the Kumamoto criteria have a favorable diagnostic performance; however, the PPV may decrease depending on the study population. Combining the Kumamoto criteria with the presence of orthopedic disease may improve the PPV.