The utility of rapid PTH radioimmunoassay in the surgical management of hyper-parathyroidism

29th Annual EANM Congress, Barcelona, Spain, October 15-19, 2016

Koutsikos J [1], Angelidis G [1], Kalogeropoulou K [1], Vogiatzis M [1], Ilia E [1], Evagelatou A [2], Velidaki A [2], Dimakopoulos N [1]

[1] Department of Nuclear Medicine, Army Share Fund Hospital (417 NIMTS), Athens, Greece
[2] Department of Nuclear Medicine, Laiko General Hospital, Athens, Greece

Introduction: Primary hyperparathyroidism is a common disease caused by single or multiple parathyroid lesions. If treatment is necessary, surgery is the commonly used procedure. Before operation, hypercalcemia and elevated parathyroid hormone (PTH) levels must be observed. Most failures in parathyroidectomies are associated with the inability to identify a multi-glandular disease or an ectopic location. Intraoperative PTH measurement (i-PTH) aims to ensure parathyroidectomy success, as the half-life of PTH is approximately 5 min. In our institution, we use an immunoradiometric assay (ELSA-PTH, CISBIO, France) for PTH measurement. The standard PTH assay in the analyzer has an 18+/-2 h incubation time, not suitable for (rapid) i-PTH measurement. Furthermore, in the literature, the methodology of radioimmunoassays is seldom used today because of lengthy turnaround time and poor diagnostic utility. However, a rapid ELSA-PTH procedure characterized by 30 min incubation time is recommended by the manufacturers. The aim of our study was to define a possible diagnostic utility of rapid ELSA-PTH procedure, compared to standard method.

Methods: 28 plasma samples were collected from patients undergoing parathyroidectomy in our hospital. The samples were analyzed according to both standard and rapid methodology. Findings were assessed by simple linear regression analysis.

Results: The mean PTH level (rapid procedure) was 170,3 nm/l (range 21.8 – 1153.4), while using the standard method was 125,2 (range 13.8 – 771.8). Higher PTH values were measured in 24/28 samples with the rapid method. Significant coefficient correlation was found between the values measured with the two methods (r=0.988, p<0.0005). There was no normal measurement based on one of the two methodologies performed corresponding to an abnormal value, when the same sample was analyzed according to the other procedure.

Conclusions: Our findings support the diagnostic value of i-PTH methodology, suggesting a favourable clinical utility in the intraoperative setting given its short incubation time. Under a well-designed protocol, this procedure can lead to a close co-operation between the operating surgeon and the specialized laboratory staff, placing the nuclear medicine department at the immediate disposal of the surgical team.

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