Technetium-99 m 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scintigraphy is excellent at reflecting the disease severity of cardiac amyloidosis (primarily transthyretin or light-chain), while technetium-99 m sodium pyrophosphate (PYP) scintigraphy is a sensitive imaging modality for identifying the extent of cardiac amyloidosis involvement, according to a study published in BMC Medical Imaging.
DPD and PYP are two of the most commonly used radiotracers for cardiac amyloidosis. For example, studies indicate that patients with transthyretin cardiac amyloidosis demonstrate moderate-to-severe DPD uptake, whereas all patients with wild-type cardiac amyloidosis demonstrate positive PYP uptake.
The authors of the study sought to directly compare both tools in assessing their effectiveness in diagnostics and quantifying disease severity. They conducted a retrospective study, reviewing the medical record of patients seen at the Samsung Medical Center who were diagnosed with cardiac amyloidosis between August 2017 and July 2020. All study patients underwent both DPD and PYP scintigraphy in a span of less than 6 months and were diagnosed with cardiac amyloidosis by experienced cardiologists.
This study made use of 12 scintigraphy parameters and 8 clinical variables (such as age, sex, NT-proBNP, and estimated glomerular filtration rate, among others). An experienced nuclear medical physician was recruited to interpret and analyze whole-body planar scans to visually confirm myocardial radiotracer uptake from a score of 0 (no uptake) to 3 (indicating strong cardiac retention uptake) using the Perugini system. With the Dorbala system, a score of 0 was defined as no cardiac retention uptake and normal bone uptake, while a maximum score of 3 demonstrated cardiac retention uptake greater than rib uptake with absent-to-mild rib uptake.
Read more about cardiac amyloidosis etiology
Ten patients with cardiac amyloidosis were enrolled. The results demonstrated that Perugini scores on DPD and PYP scans demonstrated a greater correlation with clinical variables compared with Dorbala scores. The researchers also found that Dorbala scores were relatively higher than Perugini scores in both DPD and PYP scans. In addition, there were relatively more cases of high visual scores in PYP scans compared with DPD scans.
Because DPD parameters showed greater associations with clinical variables than PYP parameters, they were deemed better at reflecting disease severity. However, because visual scores were more commonly higher in PYP scans compared with DPD scans, they were seen as more useful in identifying cardiac amyloidosis involvement.
Reference
Park YJ, Lee J, Kim D, et al. Direct comparison of diagnostic and clinical values between Tc-99 m DPD and Tc-99 m PYP scintigraphy in patients with cardiac amyloidosis. BMC Med Imaging. Published online July 17, 2023. doi:10.1186/s12880-023-01054-x
