Multicentre evaluation of a new point-of-care test for the determination of NT-proBNP in whole blood

BACKGROUND: The Roche CARDIAC proBNP point-of-care (POC) test is the first test intended for the quantitative determination of N-terminal pro-brain natriuretic peptide (NT-proBNP) in whole blood as an aid in the diagnosis of suspected congestive heart failure, in the monitoring of patients with compensated left-ventricular dysfunction and in the risk stratification of patients with acute coronary syndromes. METHODS: A multicentre evaluation was carried out to assess the analytical performance of the POC NT-proBNP test at seven different sites. RESULTS: The majority of all coefficients of variation (CVs) obtained for within-series imprecision using native blood samples was below 10% for both 52 samples measured ten times and for 674 samples measured in duplicate. Using quality control material, the majority of CV values for day-to-day imprecision were below 14% for the low control level and below 13% for the high control level. In method comparisons for four lots of the POC NT-proBNP test with the laboratory reference method (Elecsys proBNP), the slope ranged from 0.93 to 1.10 and the intercept ranged from 1.8 to 6.9. The bias found between venous and arterial blood with the POC NT-proBNP method was < or =5%. All four lots of the POC NT-proBNP test investigated showed excellent agreement, with mean differences of between -5% and +4%. No significant interference was observed with lipaemic blood (triglyceride concentrations up to 6.3 mmol/L), icteric blood (bilirubin concentrations up to 582 micromol/L), haemolytic blood (haemoglobin concentrations up to 62 mg/L), biotin (up to 10 mg/L), rheumatoid factor (up to 42 IU/mL), or with 50 out of 52 standard or cardiological drugs in therapeutic concentrations. With bisoprolol and BNP, somewhat higher bias in the low NT-proBNP concentration range (<175 ng/L) was found. Haematocrit values between 28% and 58% had no influence on the test result. Interference may be caused by human anti-mouse antibodies (HAMA) types 1 and 2. No significant influence on the results with POC NT-proBNP was found using volumes of 140-165 muL. High NT-proBNP concentrations above the measuring range of the POC NT-proBNP test did not lead to false low results due to a potential high-dose hook effect. CONCLUSIONS: The POC NT-proBNP test showed good analytical performance and excellent agreement with the laboratory method. The POC NT-proBNP assay is therefore suitable in the POC setting.

Oxidative stress and damage in liver, but not in brain, of Fischer 344 rats subjected to dietary iron supplementation with lipid-soluble [(3,5,5-trimethylhexanoyl)ferrocene]

Accumulation of iron probably predisposes the aging brain to progressive neuronal loss. We examined various markers of oxidative stress and damage in the brain and liver of 3- and 24-month-old rats following supplementation with the lipophilic iron derivative [(3,5,5-trimethylhexanoyl)ferrocene] (TMHF), which is capable of crossing the blood-brain barrier. At both ages, iron concentration increased markedly in the liver but failed to increase in the brain. In the liver of TMHF-treated young rats, levels of alpha- and gamma-tocopherols and glutathione (GSH) were also higher. In contrast, the brain displayed unaltered levels of the tocopherols and GSH. Malondialdehyde (MDA) level was also higher in the cerebrospinal fluid (CSF) and the liver but not in the brain. In old rats, the absence of an increase in iron concentration in the brain was reflected by unaltered concentrations of GSH, tocopherols, and MDA as compared to that in untreated rats. In the aging liver, concentrations of GSH and MDA increased with TMHF treatment. Morphological studies revealed unaltered levels of iron, ferritin, heme oxygenase-1 (HO-1), nitrotyrosine (NT), or MDA in the brains of both young and old rats treated with TMHF. In contrast, TMHF treatment increased the level of HO-1 in Kupffer cells, NT in hepatic endothelial cells, and MDA and ferritin in hepatocytes. Although these results demonstrated an increase in the biochemical markers of oxidative stress and damage in response to increasing concentrations of iron in the liver, they also demonstrated that the brain is well protected against dietary iron overload by using iron in a lipid-soluble formulation.

NT-proBNP in patients with out-of-hospital cardiac arrest: Results from the FINNRESUSCI Study

AIM To assess whether the established cardiovascular biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP) provides prognostic information in patients with out-of-hospital cardiac arrest due to ventricular tachycardia or fibrillation (OHCA-VT/VF). METHODS We measured NT-proBNP levels in 155 patients with OHCA-VT/VF enrolled into a prospective multicenter observational study in 21 ICUs in Finland. Blood samples were drawn <6h of OHCA-VT/VF and later after 24h, 48h, and 96h. The end-points were mortality and neurological outcome classified according to Cerebral Performance Category (CPC) after one year. NT-proBNP levels were compared to high-sensitivity troponin T (hs-TnT) levels and established risk scores. RESULTS NT-proBNP levels were higher in non-survivors compared to survivors on study inclusion (median 1003 [quartile (Q) 1-3 502-2457] vs. 527 [179-1284]ng/L, p=0.001) and after 24h (1913 [1012-4573] vs. 1080 [519-2210]ng/L, p<0.001). NT-proBNP levels increased from baseline to 96h after ICU admission (p<0.001). NT-proBNP levels were significantly correlated to hs-TnT levels after 24h (rho=0.27, p=0.001), but not to hs-TnT levels on study inclusion (rho=0.05, p=0.67). NT-proBNP levels at all time points were associated with clinical outcome, but only NT-proBNP levels after 24h predicted mortality and poor neurological outcome, defined as CPC 3-5, in models that adjusted for SAPS II and SOFA scores. hs-TnT levels did not add prognostic information to NT-proBNP measurements alone. CONCLUSION NT-proBNP levels at 24h improved risk assessment for poor outcome after one year on top of established risk indices, while hs-TnT measurements did not further add to risk prediction.