Biological Variation of Ischaemia-Modified Albumin in Healthy Subjects : Cardiovascular Topic

Aim : Ischaemia-modified albumin (IMA); as measured by the albumin-cobalt binding (ACB) testr; has been cleared by the US Food and Drug administration as a biomarker to exclude the presence of myocardial ischaemia in patients. Although there are a number of published studies detailing the clinical utility of IMA; data on the biological variation of IMA are still lacking. In this study we determined the analytical and biological variance components of ischaemia-modified albumin; and compared the distribution of IMA values in our patient population to those provided by the kit manufacturer. Methods : IMA was determined once a week for five consecutive weeks on a cohort of healthy subjects using a colorimetric method; the ACB testr on a Roche modular analyser. Results : The analytical coefficient of variation (CVA) was 5; and the within-subject (CVI) and between-subject (CVG) biological variations were 3 and 7; respectively. Analysis of the repeated measures with gender and race (black and Caucasian) as between-subject factors; and weeks (1-5) as the within-subject factor showed that gender had no significant effect on circulating IMA concentrations (p = 0.3146); whereas race did have a significant effect (p = 0.0062). A significant (p = 0.0185) interaction was observed between gender and race. Conclusion : The ACB testr could bring a new dimension to the care and management of patients with acute coronary syndrome. Further studies for normal population distributions by gender and ethnicity; and an optimum cut-off value appear to be required

NT-proBNP and the Diagnosis of Exercise-Induced Myocardial Ischaemia : Cardiovascular Topic

Background : Amino terminal pro-B-type natriuretic peptide (NT-proBNP) is a sensitive marker of ventricular dysfunction. Exercise causes an increase in the secretion of NT-proBNP; and with myocardial ischaemia the increase is more pronounced. This increase has been found to improve the diagnostic sensitivity of the stress ECG in diagnosing myocardial ischaemia in subjects with normal ventricular function. Objective : To assess whether the change in NT-proBNP can be used to diagnose effort-induced myocardial ischaemia in an unselected population. Methods : We enrolled a total of 51 consecutive patients; referred for exercise stress 99mTc-sestamibi SPECT MPI (single-photon emission computed tomography myocardial perfusion imaging) to diagnose inducible myocardial ischaemia. NT-proBNP was determined at rest and 30 minutes after cessation of exercise. Results : Of the 51 patients; 28 had normal perfusion scans; seven had scans with fixed perfusion defects (previous myocardial infarction with no inducible ischaemia) and 16 had reversible perfusion defects (inducible ischaemia). There was no correlation between ischaemia and resting NT-proBNP; post-stress NT-proBNP or the change in NT-proBNP (delta-NT-proBNP). Conclusion : In an unselected population the change in NT-proBNP cannot be used to diagnose effort-induced myocardial ischaemia

Validated method for quantitation of biomarkers for benzene and its alkylated analogues in urine.

A validated gas chromatography-mass spectrometric method for the analysis of the metabolites of benzene and its alkylated analogues in urine is reported. A number of metabolites, as required by authorities for biomonitoring of industrial exposure to aromatic vapour, were analysed simultaneously with preservation of quantitative information concerning positional isomers. The use of this method replaces a combination of analytical methods required for the analysis of all these metabolites. Urine samples were subjected to acidic deconjugation followed by a derivatization step. Phenol, ortho-, meta-, para-cresol, mandelic acid, and ortho-, meta-, para-methylhippuric acid were analysed as their corresponding ethoxycarbonyl derivatives, with single ion monitoring. The mass-to-charge ratios (m/z) of the ions used for quantitation by single ion monitoring of the metabolites were: phenol, 94 m/z; cresols, 108 m/z; mandelic acid, 206 m/z; hippuric acid, 105 m/z; methylhippuric acids, 119 m/z. The mass-to-charge ratios for the internal standards were: [(2)H(6)]phenol, 99 m/z; p-chlorophenol, 128 m/z and 3-chloro-4-hydroxyphenyl acetic acid, 214 m/z. The limits of detection for phenol and the cresols were below 0.4 micromol/l and below 0.05 micromol/l for mandelic acid and the hippuric acids. Within-run precision for mandelic acid was 6.2%, for hippuric acid was 7.32% and was below 5% for the rest of the analytes.