accuracy of 99mtc-hydroxymethylene diphosphonate scintigraphy for diagnosis of transthyretin cardiac amyloidosis

Either 99mtechnetium diphosphonate (tc-dpd) or pyrophosphate (tc-pyp) scintigraphy plays a relevant role in diagnosing transthyretin cardiac amyloidosis (ca), and labeled radiotracers have been extensively studied in diagnosing ca. few studies have analyzed and validated 99mtc-hydroxymethylene diphosphonate (tc-hmdp). our aim was to validate the diagnostic accuracy of tc-hmdp total-body scintigraphy in a cohort of patients with biopsy-proven transthyretin ca. we retrospectively evaluated all patients undergoing 99mtc-hmdp total-body scintigraphy, in adjunct to a comprehensive diagnostic work-up for suspected ca. sixty-five patients were finally diagnosed with ca, while it was excluded in 20 subjects with left ventricular hypertrophy of various etiologies. twenty-six patients had al-ca, 39 had ttr ca (16 ttrm, 23 ttrwt). at tc-hmdp scintigraphy, 2 al patients showed a perugini score grade 1 heart uptake, while 24 showed no uptake. all ttr patients showed tc-hmdp uptake, with three patients showing a perugini score grade 1, 16 grade 2, and 20 grade 3, respectively. no uptake was observed in patients with left ventricular hypertrophy. a positive tc-hmdp scintigraphy showed a 100% sensitivity and a 96% specificity for ttr ca identification. tc-hmdp scintigraphy is as accurate as tc-dpd or tc-pyp, and therefore de facto be considered a valuable tool for the diagnosis of ttr ca.