DPD Grade 1 Interpretation — EECC MCQ
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Correct answer: A — Grade 1 DPD uptake is indeterminate — it does not reliably diagnose ATTR amyloidosis (unlike Grade 2-3 which has ≥99% PPV); endomyocardial biopsy may be needed for definitive diagnosis if clinical suspicion remains high
DPD/HMDP/PYP bone scintigraphy grading for cardiac amyloidosis: Grade 0 = no uptake (excludes ATTR with high NPV); Grade 1 = mild uptake, less intense than bone (INDETERMINATE — sensitivity ~60-70% for ATTR; can also occur in AL amyloidosis ~20%); Grade 2 = uptake equal to bone; Grade 3 = uptake greater than bone. The non-invasive diagnostic pathway (Gillmore criteria) requires Grade 2-3 uptake WITH negative monoclonal protein studies for ≥99% PPV for ATTR. Grade 1 uptake does NOT meet this threshold and requires: (1) careful clinical assessment; (2) consideration of endomyocardial biopsy if suspicion remains high; (3) exclusion of AL amyloidosis (even with normal free light chains, immunofixation and bone marrow biopsy may be needed). The 2023 ESC Cardiomyopathy Guidelines emphasise that Grade 1 cannot be used for non-invasive ATTR diagnosis.
Reference: ESC (2023): Cardiomyopathies; Gillmore et al. Circulation 2016