ECE2020 Audio ePoster Presentations Thyroid (144 abstracts)
1University of Paduva, Endocrinology Unit, Department of Medicine (DIMED), Padua, Italy; 2Division of Endocrine and Metabolic Diseases, IRCCS Istituto Auxologico Italiano, Milan, Italy; 3Alma Mater Studiorum – University of Bologna, Endocrinology Unit and Centre for Applied Biomedical Research, Department of Medical and Surgical Sciences, S. Orsola-Malpighi Hospital, Bologna, Italy; 4University of Padua, Department of Laboratory Medicine, Padua, Italy
Background: Calcitonin (CT) is the most sensitive marker for MTC diagnosis. By the way, many pre-analytical, analytical and post-analytical pitfalls worsen its accuracy. Procalcitonin (proCT), a CT precursor, has been suggested as a valuable complementary test in MTC diagnosis, given its stability and the reproducibility between different assay kits.
Material and Methods: basal CT (bCT) and proCT (bproCT) and stimulated CT (bCT) and proCT (sproCT) (2–5–10 and 20 minutes)were measured in 37 patients (14M, 23F; median age: 55 years, range: 5–77 years) that underwent surgical excision. At the histological report, 22 were MTC, while the others were C-cell hyperplasias (HCCs) or non-C-cell lesions. 17/37 (45.9%) were carriers of a RET mutation. Calcium gluconate at the dose of 25 mg/Kg based on adjusted body weight was administered. bproCT was considered positive when ≥ 0.04 mg/l, while CT when ≥ 10 ng/l.
Results: there was a correlation between bCT and bproCT (P < 0.0001, r = 0.75). A significant correlation was found between MTC tumor size and bproCT (P = 0.0062, r = 0.58), as well as with bCT (P = 0.01, r = 0.54).Positive bproCT showed higher specificity than positive bCT in the diagnosis of MTC with respect to non MTC lesions (CCHs or other lesions) (53% vs 40%), with higher positive predictive value (PPV) (70% vs 66.6%). The combination of elevated bCT and bproCT increased the specificity of bCT value from 40% to 67% and its PPV from 67% to 75%. bCT and bproCT showed the same accuracy in RET-wild-type (RETwt) and RET-mutated patients. Applying ROC curve, we could identify a cut-off of 0.07 mg/l for bproCT, able to identify a MTC (sensitivity = 68%, specificity = 87%, AUC = 0.764, P = 0.0009), regardless of the gender. There was a correlation between sCT and sproCT (P < 0.0001, r = 0.64). A positive correlation existed between MTC tumor size and sproCT (P = 0.0018, r = 0.64) and with sCT (P = 0.0001, r = 0.75). Higher values of median proCT increase were found in MTC versus non-MTC (median increase of 0.22 mg/l in MTC versus 0.02 mg/l in non-MTC, P = 0.0003). Applying the ROC curve, a sproCT value > 0.19 was able to identify an MTC (sensitivity = 72%, specificity = 93%, AUC: 0.806, P < 0.001), regardless of the gender. Combining bproCT and sproCT specificity for MTC increased up to 93% (94% VPP).
Conclusions: proCT calcium-stimulated levels are significantly higher in MTC than in non-MTC and are correlate with tumour size. Basal and stimulated proCT can be used in combination with bCT and sCT to increase its specificity in biochemical diagnosis of MTC.