Stability of total plasma homocysteine in perinatology

Synthesis and Characterization of Anionic Triazine Dendrimers with a Labile Disulfide Core

Anionic dendrimers based on melamine with disulfide bonds at the core were prepared to investigate the solubility of these architectures, the ability of these molecules to solubilize pyrene as a model drug, and the ability of these architectures to undergo thiol-disulfide exchange. The ability to solubilize pyrene is directly correlated with molecular weight of the dendrimer-aggregation of dendrons does not occur. Thiol-disulfide exchange occurs rapidly using dithiothreitol as the reductant to yield dendrimers with thiol cores that can undergo oxidation in air to yield the original dendrimer.

Comparison of soluble thrombomodulin, von Willebrand factor, tPA/PAI-1 complex, and high-sensitivity CRP concentrations in serum, EDTA plasma, citrated plasma, and acidified citrated plasma (Stabilyte™) stored at −70 °C for 8–11 years

The aim was to define the most suitable specimen collection tubes for measurements of soluble Thrombomodulin (sTM), von Willebrand factor (vWF), and tPA/PAI-1 complex concentrations, and in particular whether the strongly acidic citrate additive in Stabilyte plasma would give significantly improved long-term stability of any of these analytes. We measured these analytes in paired specimens from 34 subjects, sampled 8-11 years before analysis, in serum, EDTA plasma, citrated plasma, and acidified citrated plasma (Stabilyte). Results were evaluated by regression analysis and Bland-Altman plots. All associations were linear across a wide assay range. Soluble TM was found to be highly unstable in serum as well as in EDTA plasma and to some extent even in ordinary citrate plasma: acidified citrate plasma is necessary to preserve sTM immunoreactivity in long-term storage. For hsCRP the slopes were not significantly different from that predicted by the dilution effect (0.83-0.86) of the citrate additive and there was no appreciable intercept. vWF values were comparable in citrate and acidified citrate plasma but serum and EDTA plasma samples yielded lower than expected results. For tPA/PAI-1 complex, Stabilyte tubes gave systematically lower results than the other tubes, with serum and EDTA plasma scoring the highest values, suggesting that in vitro increase in complex levels takes places upon blood collection and/or storage. We conclude that Stabilyte plasma is the specimen collection tube of choice for biobank projects aiming to measure fibrinolytic factors as well as several other analytes in the clotting system, such as soluble thrombomodulin and von Willebrand factor, in addition to the inflammatory marker hs-CRP. Indeed, using acidified Stabilyte plasma as the single medium would substantially simplify sampling for many epidemiological studies.

Unexpected relationship between plasma homocysteine and intrauterine growth restriction

BACKGROUND

Moderate hyperhomocysteinemia is considered a risk factor for thrombosis and atherosclerosis. We hypothesized that higher maternal and newborn homocysteine concentrations in plasma would increase the risk of intrauterine growth restriction through placental thrombosis.

METHODS

We carried out a case-control study that included all cases born at our institution over a 2-year period whose birthweight was below the 10th percentiles for gestational age and sex according to Canadian norms; controls were born at the same period and institution at or above the 10th percentiles and were matched on gestational age, race, and sex. Homocysteine was measured in cord and maternal blood. The analysis included 483 case and 468 control mothers and 409 case and 438 control newborns.

RESULTS

Homocysteine values were largely <15 micromol/L. Contrary to expectation, within that range of values, increased plasma homocysteine, particularly in the mother, was protective against intrauterine growth restriction. With the case/control status as the outcome, the estimated odds ratio was 0.37 (95% confidence interval, 0.24-0.58) for a 5 micromol/L unit difference on the maternal homocysteine scale. With birthweight as the outcome, the estimated increase was 178.1 g (95% confidence interval, 92.5-263.7 g) for every 5 micromol/L unit increase in maternal homocysteine. Results were similar using newborn homocysteine concentrations.

CONCLUSIONS

The data suggest that, in contrast to the proposed hypothesis, mothers with small babies have lower homocysteine concentrations than those giving birth to larger ones.