Short-term increases of plasma cardiac troponin I are better evaluated by comparison with the reference change value

Introduction: We have investigated consecutive troponin I measurements using the Reference Change Value (RCV) at low concentrations, in patients admitted in Emergency Department (ED). Materials and methods: Patients admitted for chest pain (N = 103) were evaluated retrospectively on the basis of two consecutive cardiac tro-ponin-I (cTn-I) tests. The second test levels exceeding the "Critical Reference Change Value" (CrRCV), a quantity calculated on the basis of the first result and the RCV of cTn-I, were considered particularly relevant. Clinical cases were analysed matching the concentration change (significative or not) with acute coronary syndrome (clinically confirmed or not). Healthy individuals (N = 70) results and internal quality control results were evaluated for the calculation of, respectively, the biological and the analytical variation of plasma cTn-I. Results: The cTn-I RCV was very high because of the high analytical variation of cTn-I in proximity of its decision limit, as shown by its imprecision profile study. Analysing data with the first result < 0.1 µg/L we have obtained an cTn-I RCV negative predictive value - NPV = 88% (95% CI = 82-92%). The 4 groups of patients have demonstrated a clinically significant difference (Chi square test; P < 0.001). Conclusions: The RCV allows to statistically evaluating the cTn-I increased levels in presence of the high imprecision of commercial cTn-I assay at low concentrations. This parameter could be applied in medical practice only for low cTn-I concentrations around the decision limit for the myocardial necrosis

Short-term increases of plasma cardiac troponin I are better evaluated by comparison with the reference change value

Introduction: We have investigated consecutive troponin I measurements using the Reference Change Value (RCV) at low concentrations, in patients admitted in Emergency Department (ED). Materials and methods: Patients admitted for chest pain (N = 103) were evaluated retrospectively on the basis of two consecutive cardiac tro-ponin-I (cTn-I) tests. The second test levels exceeding the "Critical Reference Change Value" (CrRCV), a quantity calculated on the basis of the first result and the RCV of cTn-I, were considered particularly relevant. Clinical cases were analysed matching the concentration change (significative or not) with acute coronary syndrome (clinically confirmed or not). Healthy individuals (N = 70) results and internal quality control results were evaluated for the calculation of, respectively, the biological and the analytical variation of plasma cTn-I. Results: The cTn-I RCV was very high because of the high analytical variation of cTn-I in proximity of its decision limit, as shown by its imprecision profile study. Analysing data with the first result < 0.1 µg/L we have obtained an cTn-I RCV negative predictive value - NPV = 88% (95% CI = 82-92%). The 4 groups of patients have demonstrated a clinically significant difference (Chi square test; P < 0.001). Conclusions: The RCV allows to statistically evaluating the cTn-I increased levels in presence of the high imprecision of commercial cTn-I assay at low concentrations. This parameter could be applied in medical practice only for low cTn-I concentrations around the decision limit for the myocardial necrosis

Improvement of neutrophil gelatinase-associated lipocalin sensitivity and specificity by two plasma measurements in predicting acute kidney injury after cardiac surgery

Introduction: Acute kidney injury (AKI) remains among the most severe complication after cardiac surgery. The aim of this study was to evaluate the neutrophil gelatinase-associated lipocalin (NGAL) as possible biomarker for the prediction of AKI in an adult cardiac population. Materials and methods: Sixty-nine consecutive patients who underwent cardiac surgeries in our hospital were prospectively evaluated. In the intensive care unit (ICU) NGAL was measured as a new biomarker of AKI besides serum creatinine (sCrea). Patients with at least two factors of AKI risk were selected and samples collected before the intervention and soon after the patient’s arrival in ICU. As reference standard, sCrea measurements and urine outputs were evaluated to define the clinical AKI. A Triage Meter for plasma NGAL fluorescence immunoassay was used. Results: Acute kidney injury occurred in 24 of the 69 patients (35%). Analysis of post-operative NGAL values demonstrated an AUC of 0.71, 95% CI (0.60 - 0.82) with a cut-off = 154 ng/mL (sensitivity = 76%, specificity = 59%). Moreover, NGAL after surgery had a good correlation with the AKI stage severity (P ≤ 0.001). Better diagnostic results were obtained with two consecutive tests: sensitivity 86% with a negative predictive value (NPV) of 87%. At 10-18 h after surgery sCrea measurement, as confirmatory test, allowed to reach a more sensitivity and specificity with a NPV of 96%. Conclusions: The assay results showed an improvement of NGAL diagnostic accuracy evaluating two tests. Consequently, NGAL may be useful for a timely treatment or for the AKI rule out in ICU patients

Alveolar Membrane Conductance Decreases as BNP Increases During Exercise in Heart Failure. Rationale for BNP in the Evaluation of Dyspnea

Background: In left ventricular failure (LVF) patients, brain natriuretic peptide (BNP), lung diffusion for carbon monoxide (DLCO), and alveolar-membrane conductance (DM) correlate with LVF severity and prognosis. The reduction of DLCO and DM during exercise reflects pulmonary edema formation. Methods and Results: To evaluate, in LVF patients, the correlation between BNP and lung diffusion parameters at rest and during exercise, we studied 17 severe LVF patients, 13 moderate, and 10 normals measuring BNP and lung diffusion parameters before, at the end, and I hour after a 10-minute high-intensity constant-workload exercise. At rest, a significant correlation exists between BNP and lung diffusion parameters. Resting BNP, DLCO, and DM correlate with peak oxygen consumption (P <.0001 for all analyses). With exercise, BNP increase is significant (severe LVF 180 49 pg/mL. moderate 68 +/- 58, normals 18 12); differently, only in severe LVF. with exercise. DLCO (-1.1 +/- 0.7 mL/mm Hg/min, P <.0001) and DM (-6.4 +/- 2.8 P <.0006) decrease. One hour after exercise, only in severe LVF, BNP is still higher than at rest, while DLCO, DM, and DM/Vc are lower. Significant correlations are observed between BNP and DM changes during exercise and recovery (P <.0001) in severe LVF. Conclusions: In severe LVE BNP changes during exercise correlate with simultaneous reductions in DM, suggesting that BNP increase and pulmonary edema formation could be related. (J Cardiac Fail 2009:15.-136-144