A multicenter study of clinical predictors of positive pyrophosphate scintigraphy findings in the diagnosis of transthyretin amyloidosis

Background: The prevalence of wild-type transthyretin (ATTR) amyloidosis is increasing with advancements in diagnostic techniques and growing awareness of the disease worldwide. ^99mTc-labeled pyrophosphate (^99mTc-PYP) scintigraphy exhibits high performance in diagnosing ATTR cardiac amyloidosis. This study aimed to validate the characteristics of patients with positive ^99mTc-PYP scintigraphy results in a multicenter setting to provide more accurate case selection criteria.

Methods and results: In total, 180 patients with suspected ATTR amyloidosis underwent ^99mTc-PYP scintigraphy in participating institutions in Japan between January 2018 and July 2022. Of 135 patients included in the analysis, 62 were ^99mTc-PYP-positive. Logistic regression analysis was performed, and the following five factors were adopted to create a scoring system, with each weighted according to its odds ratio value; 1 point was scored for the absence of hypertension, existence of peripheral entrapment neuropathy (carpal tunnel syndrome or spinal canal stenosis), conduction disturbance (the presence of QRS complex ≥120 ms, first-degree atrioventricular block, higher degree of atrioventricular block, or presence of pacemaker implantation), and left ventricular hypertrophy and 2 points for troponin I/T ≥ 0.06 ng/mL. ^99mTc-PYP scintigraphy positivity rate in the 0-point group was 0 %, whereas that in the 6-point group was 100 %. The area under the curve of the criteria was 0.820 (95 % confidence interval, 0.752-0.888; P < 0.001).

Conclusions: The combination of clinical information, which is easily available in local clinics, can provide accurate pretest prediction of positive ^99mTc-PYP scintigraphy results. This will help clinicians to make an early diagnosis of ATTR amyloidosis.