Clinical evaluation of capillary B-type natriuretic peptide testing.

Background Capillary B-type natriuretic peptide (BNP) testing is attractive in outpatient and emergency settings. The aim of this study was to perform an evaluation of the clinical performances of capillary BNP testing as compared with venous whole blood and plasma point-of-care (POC) BNP as well as plasma N-terminal (NT) proBNP central laboratory testing. Methods BNP was measured with a novel single epitope POC assay (Minicare® BV, Eindhoven, The Netherlands) and NT-proBNP with a central laboratory assay (Roche Diagnostics®, Vienna, Austria). Results BNP and NT-proBNP were measured in 269 patients of a Department of Cardiology (mean age 67.9 ± 13 years, 26.4% females). Capillary BNP very closely correlated with whole blood venous BNP (r = 0.99, p < 0.001). There was also a close correlation of plasma BNP and NT-proBNP concentrations (r = 0.79, p < 0.001). The diagnostic performances of capillary BNP, whole blood venous BNP, plasma BNP and plasma NT-proBNP for acute heart failure (areas under receiver operating characteristic curves [AUC ROC]: 0.73-0.77) or systolic left ventricular dysfunction in the whole study population (AUC ROC: 0.72-0.76) did not differ significantly. All were significant independent predictors of cardiovascular death during follow-up of the whole study population. Conclusions Our study for the first time demonstrated a very close correlation of capillary and venous whole blood or plasma BNP concentrations using the same BNP assay in a large patient cohort. The diagnostic performances of different BNP specimens did not differ significantly, and no significant differences between BNP and NT-proBNP were found either.

Equal clinical performance of a novel point-of-care cardiac troponin I (cTnI) assay with a commonly used high-sensitivity cTnI assay.

BACKGROUND: Efficient rule-out of acute myocardial infarction (MI) facilitates early disposition of chest pain patients in emergency departments (ED). Point-of-care (POC) cardiac troponin (cTn) may improve patient throughput. We compared the diagnostic accuracy of a novel cTnI test (Minicare cTnI, Philips), with current POC cTnI (I-Stat, Abbott) and high-sensitivity central laboratory cTnI (hs-cTnI; Architect, Abbott) assays. METHODS: The clinical performance of the assays were compared in samples from 450 patients from a previous clinical evaluation of Minicare cTnI. RESULTS: Minicare cTnI correlated with Architect hs-cTnI (r2=0.85, p<0.0001) and I-Stat cTnI (r2=0.93, p<0.0001). Areas under the receiver operating characteristics curves were 0.87-0.91 at admission (p=ns) and 0.96-0.97 3h after admission (p=ns). The negative predictive values (NPV) at admission were 95% ((92-97%, 95% CI) for Minicare cTnI and increased to 99% (97-100%) at 2-4h, and similar to Architect hs-cTnI (98%, 96-100%), but higher than I-Stat cTnI (95%, 92-97%; p<0.01). Negative likelihood ratios (LR-) after 2-4h were 0.06 (0.02-0.17, 95% CI) for Minicare cTnI, 0.11 (0.05-0.24) for Architect hs-cTnI (p=0.02) and 0.28 (0.18-0.43) for I-Stat cTnI (p<0.0001). The clinical concordances between Minicare cTnI and Architect hs-cTnI were 92% (admission) and 95% (2-4h), with lower concordances between Minicare cTnI and I-Stat cTnI (83% and 78%, respectively; p=0.007). CONCLUSIONS: The Minicare cTnI POC assay may become useful for prompt and safe ruling-out of AMI in ED patients with suspected AMI using a guideline supported 0/3h sampling protocol.

Analytical evaluation of a new point of care system for measuring cardiac Troponin I.

OBJECTIVES: Point-of-care cardiac troponin testing with adequate analytical performances has the potential to improve chest pain patients flow in the emergency department. We present the analytical evaluation of the newly developed Philips Minicare cTnI point-of-care immunoassay. DESIGN & METHODS: Li-heparin whole blood and plasma were used to perform analytical studies. The sample type comparison study was performed at 4 different hospitals. The 99th percentile upper reference limit (URL) study was performed using Li-heparin plasma, Li-heparin whole blood and capillary blood samples from 750 healthy adults, aging from 18 to 86years. RESULTS: Limit of the blank, limit of detection and limit of quantitation at 20% coefficient of variation (CV) were determined to be 8.5ng/L, 18ng/L and 38ng/L respectively without significant differences between whole blood and plasma for LoQ. Cross-reactivity and interferences were minimal and no high-dose hook was observed. Total CV was found to be from 7.3% to 12% for cTnI concentrations between 109.6 and 6135.4ng/L. CV at the 99th percentile URL was 18.6%. The sample type comparison study between capillary blood, Li-heparin whole blood and Li-heparin plasma samples demonstrated correlation coefficients between 0.99 and 1.00 with slopes between 1.03 and 1.08. The method comparison between Minicare cTnI and Beckman Coulter Access, AccuTnI+3 demonstrated a correlation coefficient of 0.973 with a slope of 1.09. The 99th percentile URL of a healthy population was calculated to be 43ng/L with no significant difference between genders or sample types. CONCLUSIONS: The Minicare cTnI assay is a sensitive and precise, clinical usable test for determination of cTnI concentration that can be used in a near-patient setting as an aid in the diagnosis of acute myocardial infarction.