A fast intraoperative PTH point-of-care assay on the Philips handheld magnotech system.

BACKGROUND: Intraoperative parathyroid hormone (ioPTH) is used during minimally invasive parathyroidectomy (MIP) to predict the success of surgery and should be accurate with a short turnaround time. MATERIAL AND METHOD: We developed an ioPTH point-of-care (POC) assay on Philips handheld magnotech system. Magnotech technology is based on magnetically controlled movement of superparamagnetic nanoparticles in stationary sample fluid. During first phase, intact-PTH is captured by magnetic particles coated with anti-N-terminal-PTH antibodies. Subsequently, magnetic particles are collected by magnetic forces at sensor surface coated with anti-C-terminal-PTH antibodies. Unbound/nonspecifically bound particles are pulled away from detection surface, using a second magnetic force. Amount of specifically bound particles is measured using a surface-sensitive optical imaging technique. RESULTS: ioPTH test could be performed with a turnaround time of less than 10 min and could detect low intact-PTH concentrations (picomolar). Integrated cartridge contains a blood separation filter and dry reagents for the assay. CONCLUSION: The next magnotech ioPTH assay will be the only POC test able to give accurate results in less than 10 min, using 25 µL of whole blood. Thanks to the ease-of-use, magnotech ioPTH could be performed in the operating theater by any member of surgical staff.

Alternative antibody for the detection of CA19-9 antigen: a European multicenter study for the evaluation of the analytical and clinical performance of the Access GI Monitor assay on the UniCel Dxl 800 Immunoassay System.

BACKGROUND: Gastrointestinal cancer antigen CA19-9 is known as a valuable marker for the management of patients with pancreatic cancer. METHODS: The analytical and clinical performance of the Access GI Monitor assay (Beckman Coulter) was evaluated on the UniCel Dxl 800 Immunoassay System at five different European sites and compared with a reference method, defined as CA19-9 on the Elecsys System (Roche Diagnostics). RESULTS: Total imprecision (%CV) of the GI Monitor ranged between 3.4% and 7.7%, and inter-laboratory reproducibility between 3.6% and 4.0%. Linearity upon dilution showed a mean recovery of 97.4% (SD + 7.2%). Endogenous interferents had no influence on GI Monitor levels (mean recoveries: hemoglobin 103%, bilirubin 106%, triglycerides 106%). There was no high-dose hook effect up to 115,000 kU/L. Clinical performance investigated in sera from 1811 individuals showed a good correlation between the Access GI Monitor and Elecsys CA19-9 (R = 0.959, slope = 1.004, intercept = +0.17). GI Monitor serum levels were low in healthy individuals (n = 267, median = 6.0 kU/L, 95th percentile=23.1 kU/L), higher in individuals with various benign diseases (n = 550, medians = 5.8-13.4 kU/L, 95th percentiles = 30.1-195.5 kU/L) and even higher in individuals suffering from various cancers (n = 995, medians = 8.4-233.8 kU/L, 95th percentiles = 53.7-13,902 kU/L). Optimal diagnostic accuracy for cancer detection against the relevant benign control group by the GI Monitor was found for pancreatic cancer [area under the curve (AUC) 0.83]. Results for the reference CA19-9 assay were comparable (AUC 0.85). CONCLUSIONS: The Access GI Monitor provides very good methodological characteristics and demonstrates an excellent analytical and clinical correlation with the Elecsys CA19-9. The GI Monitor shows the best diagnostic accuracy in pancreatic cancer. Our results also suggest a clinical value of the GI Monitor in other cancers.

Proposal of a candidate international conventional reference measurement procedure for free thyroxine in serum.

In the present paper the IFCC WG-STFT recommends and provides the rationale to establish metrological traceability of serum free thyroxine (FT4) measurements to a candidate international conventional reference measurement procedure. It is proposed that this procedure be based on equilibrium dialysis combined with determination of thyroxine in the dialysate with a trueness-based reference measurement procedure. The measurand is thus operationally defined as "thyroxine in the dialysate from equilibrium dialysis of serum prepared under defined conditions". With regard to the trueness-based reference measurement procedure, the WG-STFT recommends use of an isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC/tandem MS) procedure for total thyroxine that has been optimized towards measurement at picomolar concentration levels and that is listed in the database of the Joint Committee for Traceability in Laboratory Medicine (JCTLM). For calibration, the purified thyroxine material IRMM-468 (resulting from a project funded by the European Commission and recently submitted to the JCTLM) is proposed. The WG-STFT stresses that according to this recommendation it is a prerequisite to strictly adhere to the defined equilibrium dialysis procedure, whereas it is permissible to introduce variants in the ID-LC/tandem MS procedure.