Sensitive and quantitative, 10-min immunofluorometric assay for D-Dimer in whole blood.

INTRODUCTION: Normal concentrations of D-Dimer can be used to exclude venous thromboembolism (VTE). However, methods for sensitive and quantitative D-Dimer measurements at the point-of-care (POC) are still limited. MATERIALS AND METHODS: We developed a 10-min, non-competitive immunofluorometric assay for D-Dimer in citrated whole blood and plasma using pre-dispensed reagents dried in single assay wells. The simple, automated assay procedure comprises a 1:50 sample dilution, one-step incubation, washing, and time-resolved fluorometric measurement directly from the wet well surface. RESULTS: The limits of detection (background + 3SD) and quantification (CV <15%) were 0.05 and 0.2 mg/L D-Dimer, respectively, and the assay was linear up to 400 mg/L. Correlations to Roche TinaQuant (r=0.726, n=200) and Biopool Auto.Dimer (r=0.190, n=149) were carried out using citrated plasma. Diagnostic sensitivity, specificity, and negative (NPV) and positive (PPV) predictive values were 98.7%, 64.4%, 99.1% and 55.1%, and 92.2%, 81.0%, 95.9% and 68.3%, respectively, using cut-off values of 0.6 and 1.0 mg/L, respectively, in outpatients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) (n=77) compared with outpatients with various other diseases (n=174). The within- and between-run CVs near the cut-off values were < or =10% in both whole blood and plasma. The 95th percentile upper range in apparently healthy individuals was 0.68 mg/L of whole blood (n=101). CONCLUSIONS: The high sensitivity and NPV suggest that the rapid immunofluorometric assay could be valuable for rapid exclusion of VTE in outpatients. With appropriate cut-offs, the assay could potentially be used as a stand-alone test or combined with clinical probability assessment, but further studies are required.

Quantitative, wide-range, 5-minute point-of-care immunoassay for total human chorionic gonadotropin in whole blood.

BACKGROUND: Human chorionic gonadotropin (hCG) is among the most common analytes available for point-of-care immunotesting, with most assays currently based on simple manual assay devices. However, as the importance of good analytical performance of rapid assays is increasingly emphasized, more sophisticated immunoassay techniques are needed to meet the future challenges of rapid yet quantitative POC testing. METHODS: We developed a simple, dry-reagent, all-in-one immunoassay for the quantitative measurement of hCG in whole blood, plasma, or serum. The noncompetitive assay equally measures intact, nicked, and hyperglycosylated hCG as well as nonnicked and nicked hCG beta-subunit with a rapid and simple procedure consisting of a 5-min, one-step incubation and, subsequent to washing, the measurement of time-resolved fluorescence directly from a wet well surface. RESULTS: The assay had a detection limit (background + 3 SD) of 0.4 IU/L hCG. The within-run CV was <15% down to 2 IU/L, and the assay was linear to 6000 IU/L. The within- and between-run CVs in heparinized whole blood and plasma were