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PTH in situ measurement in patients with hyperparathyroidism: single-centre experience of 179 patients.

CONTEXT
The measurement of PTH in situ (PTHis) by fine-needle aspiration (FNA) is proposed as a tool to preoperatively help localize parathyroid glands detected on ultrasound. However, the accuracy of PTHis is highly variable according to the few available studies. We aimed to develop and validate the PTHis procedure. We assessed the performance of PTHis in a large series of patients with hyperparathyroidism.


PATIENTS
The technique setup consisted of PTHis measurement in thyroid samples from patients with thyroid nodules and patients with high circulating PTH levels (tertiary hyperparathyroidism). Consecutive patients were recruited and submitted to ultrasound-guided FNA-PTHis determination.


RESULTS
During the method setup, we obtained undetectable PTHis levels in all non-parathyroid tissues after sample dilutions. PTHis was higher in patients with hyperparathyroidism (n=145, 1817±3739 ng/L, range <4.6-31,140) than in those with thyroid or undetermined cervical lesions (n=34, <4.6 ng/mL,p<0.0001). When evaluating PTHis performance in histologically proven samples (158 lesions from 121 patients), PTHis was detectable in 85/97 parathyroid lesions (87%, range 22-31,140 ng/L) and undetectable in all non-parathyroid lesions (n=61,p<0.0001). The specificity and positive predictive value were 100%, and the sensitivity was 87.6%. False-negative lesions (n=12) were smaller (9.4±5.9 mm) and more often consisted of hyperplasias (75%) than true-positive lesions (16.1±8.4 mm and 33%, p=0.009 and p=0.0089, respectively). The method was safe and well tolerated. Four educational cases are also provided.


CONCLUSIONS
PTHis determination is a safe and well-tolerated procedure that enhances the specificity of ultrasound-detected lesions. If accurately set up, it confirms the parathyroid origin of uncharacterized cervical lesions.