# Interpreting the drop: concordance and disparity between a new point-of-care assay and laboratory intraoperative parathyroid hormone testing in parathyroid surgery

## TL;DR

A new point-of-care test for parathyroid hormone shows bigger drops than lab tests after surgery, which could affect surgical decisions.

## Contribution

The study evaluates a new point-of-care assay's reliability compared to lab tests during parathyroid surgery.

## Key findings

- The NBCL CONNECT assay shows significantly higher percentage PTH drops than lab tests at 5 and 10 minutes post-excision.
- Bland-Altman analysis shows wide agreement limits between the two methods.
- The assay is reliable for baseline PTH but may lead to false results in post-excision measurements.

## Abstract

To evaluate the concordance of the NBCL CONNECT Point-of-Care (POC) Intraoperative Parathyroid Hormone (IOPTH) assay with a Central Laboratory standard, with a focus on percentage drops and the usefulness of POC testing in parathyroid surgeries.

In this prospective single-centre study (Nov 2023-May 2025), blood samples were drawn from patients undergoing parathyroidectomy for simultaneous analysis on the NBCL CONNECT POC assay and the central laboratory platform. The timing of the blood sample would typically be at induction of anaesthesia, 5 min and 10 min post-excision. Statistical analyses were performed using Python with the SciPy and Matplotlib libraries. Wilcoxon signed-rank test was used to determine the presence of a systematic difference between the two assays. Bland-Altman analysis was performed to calculate the mean difference and the 95% limits of agreement. Pearson correlation coefficient was used to evaluate the linear relationship between the two methods.

Fifty-seven consecutive patients were identified and included in this study. No significant difference was found at baseline (p = 0.943) or 5 min (p = 0.098). However, a statistically significant difference emerged at 10 min (p = 0.003). Bland-Altman analysis revealed wide limits of agreement at all time points and correlation between the methods was poor at the 10-minute mark (r = 0.11). The mean percentage PTH drop reported by NBCL CONNECT was significantly greater than the laboratory values at both 5 min (58.6% vs. 49.0%, p = 0.001) and 10 min (51.2% vs. 36.2%, p = 0.009).

The NBCL CONNECT provides a reliable baseline PTH measurement but consistently reports a larger percentage drop post-excision. Surgeons using this assay must be aware of its specific characteristics and the potential for both false-positive and false-negative results to ensure optimal surgical outcomes.

Not applicable.