Validation of the Kumamoto criteria for prediction of 99m technetium pyrophosphate scintigraphy positivity as a strategy for diagnosis of transthyretin cardiac amyloidosis: A retrospective cohort study in Kochi

Background Early diagnosis of transthyretin cardiac amyloidosis (ATTR-CA) is important. The aim of this study was to validate the ‘Kumamoto criteria’ for prediction of technetium-99m pyrophosphate (99mTc-PYP) scintigraphy positivity. Methods One hundred fifty patients (median age: 79.4 years, 117 males) with the possibility of ATTR-CA who underwent 99mTc-PYP scintigraphy were assessed. We divided the patients into 4 groups (groups with score of 0–3) according to the Kumamoto criteria by total points for the following 3 factors: high-sensitivity cardiac troponin T (hs-cTnT) ≥0.0308 ng/ml, left ventricle posterior wall thickness ≥13.6 mm, and wide QRS (QRS ≥ 120 ms). Results Seventy patients (46.7%) were positive for 99mTc-PYP scintigraphy. 99mTc-PYP positivity rates in the groups with score of 0, 1, 2, and 3 were 4%, 39%, 69%, and 89%, respectively. Compared with the original Kumamoto cohort, our patients in the score 1 group showed a relatively high rate of 99mTc-PYP positivity because hs-cTnT as one of the positive factors had high ability to discriminate the disease. The sensitivity and negative predictive value of hs-cTnT ≥0.0308 ng/ml for 99mTc-PYP positivity were 97.1% and 93.9%. Conclusions In the Kochi validation cohort, the Kumamoto criteria were useful for predicting 99mTc-PYP positivity. However, patients in the score 1 group should be assessed cautiously for the possibility of ATTR-CA if the hs-cTnT value is high.