Our results show that higher plasma concentrations of tHcy after an acute intense exercise are associated to higher concentrations of rHcy, and this effect is independent of the type of exercise, vitamin status, or amino acid metabolic stress but could be related to potential changes in the renal function.

Background: Serum cardiac troponin T concentrations are important predictors of cardiovascular and all-cause mortality in end-stage renal disease. In patients with end-stage renal disease, assessment of serial results is essential to distinguish between a cardiovascular event and chronic elevation. We employed a high-sensitivity serum cardiac troponin T assay to evaluate the long-term biological variation in end-stage renal disease patients and in healthy individuals; these biological variation data were used to define the reference change value and the analytical goals. Methods: Serum samples were collected from 18 end-stage renal disease patients in steady-state conditions, one per month for 6 months, and from 11 healthy volunteers at weekly intervals over 5 weeks. Biological variation data were derived using analysis of variance. Results: Baseline serum cardiac troponin T concentrations in end-stage renal disease patients were above the 99th percentile of the healthy population and increased with duration of haemodialysis. For end-stage renal disease patients, within-subject (CV I ) and between-subject (CV G ) coefficients of variation were 14.7 and 77.8%, respectively, whereas these were 5.9 and 30.4%, respectively, for healthy individuals. The derived two-tailed and one-tailed reference change values were 44.1 and 37.1%, respectively, for end-stage renal disease patients, and 21.6 and 18.2% for healthy subjects. Conclusions: For appropriate clinical management of end-stage renal disease patients in the context of a cardiovascular event, regular monitoring of serum cardiac troponin T concentrations could be important in order to allow future comparison through reference change value. Biological variation data in end-stage renal disease patients were significantly higher than for healthy individuals; therefore, the use of proper reference change value data is recommended. Moreover, the observed CV I values provide demanding imprecision goals for current technology.

Background: Biological variation data for free plasma amino acids are lacking from the more comprehensive databases. Therefore, we determined the intra-and inter-individual components of variation in healthy subjects. These data were used to define desirable goals for imprecision, bias and total error, indices of individuality and reference change values. Methods: Plasma samples were collected from 11 volunteers at weekly intervals over 5 weeks. Free plasma amino acids were analyzed by reversed-phase HPLC and analytical and biological variation data were derived using ANOVA. Results: Intra-individual coefficients of variation ranged from 9.5% to 46.4%, with lower values among the essential amino acids. The mean inter-individual coefficient of variation was 46.6% and was higher than intra-individual values for all amino acids. Thus, indices of individuality were below 0.8. Reference change values ranged from 30.9% to 128.4% and total error values ranged from 15.2% to 61.0%. Conclusions: Plasma amino acids exhibit relatively low intra-individual coefficients of variation, with essential amino acids showing tighter homeostatic control. Analytical quality goals can be reasonably achieved with current methods. Reference intervals are of limited value in the detection of unusual results in an individual. Therefore, comparison of serial results by means of the reference change values is recommended. Clin Chem Lab Med 2010;48:99-104.

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Fetal nucleated red blood cells (NRBC) have been widely reported in maternal blood during pregnancy. However, there is no consensus with regard to their presence in all pregnancies. Therefore, the usefulness of developing a fetal NRBC-based noninvasive method suitable for clinical prenatal diagnosis remains uncertain. Fluorescence in situ hybridization (FISH) method was used to evaluate the ability of one of our own monoclonal antibodies (mAb), 2B7.4, to isolate fetal NRBC from maternal blood by magnetic activated cell sorting (MACS). Our mAb was able to isolate from 25 to 822 NRBC from all of the 45 maternal blood samples included in this study. A correct diagnosis was achieved in 21 out of 24 pregnancies carrying trisomic fetuses (87.5%), with a fetal/maternal NRBC frequency of 8.4%. In contrast, a significantly lower percentage of fetal NRBC (0.2%) was observed in 22% of pregnancies carrying a chromosomally normal male fetus, that were correctly predicted. In conclusion, using 2B7.4 mAb we succeeded in isolating NRBC from the maternal blood samples, but most of the isolated cells were maternal in origin. Nevertheless, a higher number of fetal NRBC was found in the peripheral blood of pregnant women carrying aneuploid fetuses, which could allow development of a screening method for prenatal diagnosis of fetal aneuploidies.

Background: Reversed-phase HPLC (RP-HPLC) has become an alternative to ion-exchange chromatography for amino acid analysis in biological fluids. However, validation studies for its urine application are limited, and the corresponding reference values have not been reported extensively. We studied the long-term performance of a commercial HPLC method for urine amino acid analysis and established specific age-related reference values for urine amino acid excretion. Methods: Method performance was continuously assessed by recovery and precision studies with urine samples and controls, respectively. Healthy individuals were prospectively analyzed throughout a 5-year period. Excretion of individual amino acids, expressed as mmol/mol of creatinine, was included in six age-related groups for random urine samples (0–1 month, 1–12 months, 1–3 years, 3–8 years, 8–16 years, and >16 years) and in two groups for 24-h urine collections (8–16 years and >16 years). Results: Over a 1-year period, CVs for retention times were <0.5% and 3.3% for within- and between-run imprecision, respectively. For amino acid concentrations, within-run CVs were 2.9–17% and between-run CVs were 7.1–46% for the same period. Amino acid recoveries were 78–122%. Reference intervals for 35 amino acids were calculated and compared with the concentrations observed in patients diagnosed with specific pathologies. A few statistically significant differences were found between the reference intervals derived using random and 24-h urine collections. Conclusions: Long-term reliability of the RP-HPLC method for urine amino acid analysis has been demonstrated. Representative age-related reference intervals for the RP-HPLC method in both random urine and 24-h urine collections have been established, and their feasibility for diagnosis of aminoaciduria has been shown. These intervals could serve as a guide for laboratories changing to HPLC methods.

This patient, on admission, presented with a tentative diagnosis of myocardial infarction: the electrocardiogram showed a nonspecific ST-segment and T-wave abnormalities, and total creatine kinase (CK; EC 2.7.3.2) activity was slightly increased (238 U/L). However, a high electrophoretic value for CK-MB (50% of total CK activity) and the electrophoretic pattern of lactate dehydrogenase (EC 1.1.1.27) isoenzymes ruled out myocardial infarction. The isoenzyme migrating as CK-MB was found later to contain no immunologically normal CK-M subunits, and it was bound to IgA. A mixture of the patient's serum and a human serum control containing all CK isoenzymes showed altered electrophoretic mobility only for CK-BB, indicating that the patient's serum contained antibodies to the B unit of CK. Elution from a Sephadex G-200 column showed that the peak at which most of the anodic CK was eluted corresponded to a molecular mass of approximately 200 kDa. Evidently this atypical isoenzyme was an IgA-CK-BB complex. Because this macro CK type 1 can mimic CK-MB, it may therefore be a source of confusion.