The Third/Second Generation PTH Assay Ratio as a Marker for Parathyroid Carcinoma: Evaluation Using an Automated Platform

Background: Parathyroid carcinoma (PCa) is rare and often difficult to differentiate initially from
benign disease. Because PCa oversecretes amino PTH that is detected by third-generation but not
by second-generation PTH assays, the normal generation PTH ( 1) is inverted in PCa (ie, 1).
Objective: The objective of the investigation was to study the utility and advantages of automated
generation PTH ratio measurements using the Liaison XL platform over existing manual
techniques.
Setting: The study was conducted at a tertiary-referral academic center.
Design: This was a retrospective laboratory study.
Subjects: Eleven patients with advanced PCa (mean age 56.0 y). The controls were patients with
1°-hyperparathyroidism (n 144;meanage 53.8 y), renal transplantation (n 41;meanage 50.6 y),
hemodialysis (n 80; mean age 65.2 y), and healthy elderly subjects (n 40; mean age 72.6 y).
Results: The median (interquartile range) generation PTH ratio was 1.16 (1.10 –1.38) in the PCa
group, which was significantly higher than the control groups: 0.74 (hemodialysis, 0.71–0.75), 0.77
(renal transplant, 0.73–0.79), 0.80 (healthy elderly, 0.74–0.83), and 0.76 (1°-hyperparathyroidism,
0.74–0.78). An inverted -generation PTH ratio ( 1) was seen in 9 of 11 PCa patients (81.8%) and
in 7 of 305 controls (2.3%), 3 of 80 hemodialysis (3.8%), and 4 of 144 1°-hyperparathyroidism
patients (2.8%). Of four PCa patients who had a normal PTH ratio with the manual method, two
had an inverted -generation PTH ratio with the automated method.
Conclusions: Study of the -generation PTH ratio in large patient populations should be feasible
using a mainstream automated platform like the Liaison XL. The current study confirms the utility
of the inverted -generation PTH ratio as a marker of PCa (sensitivity: 81.8%; specificity: 97.3%).