28 research outputs found
Blood levels of homocysteine, folate, vitamin B-6 and B-12 in women using oral contraceptives compared to non-users
No full textBackground and objectives: To compare the levels of total homocysteine (tHcy), folate, vitamin B-6 and B-12, in women not using oral contraceptives (OC) vs. those using OC. Materials and methods: 219 healthy women were enrolled in the study; 159 of them had not been using OC for at least 12 months prior to their enrolment, while 60 were on regular OC treatment. Results: The median levels of vitamin B-6 and B-12 were significantly lower in OC users than in non-users (24.2 vs. 32.9 nmol/l, p = 0.029; 278 vs. 429 ng/ml, p < 0.001). There were no statistically significant differences in the levels of tHcy (fasting and post-methionine loading) and folate. Conclusions: In our cross-sectional study, OC use was associated with low vitamin B-6 and B-12 levels. Since low vitamin B-6 levels are independently associated with heightened risks for arterial and venous thromboembolism (TE), they could partly account for the increased TE risk of OC users
Determination of total homocysteine in plasma: comparison of the Abbott Imx immunoassay with high performance liquid chromatography
No full textBackground and Objectives. The aim of this study was to compare the performance of a commercially available IMx immunoassay with that of a reversed-phase high performance liquid chromatography (HPLC) method for measuring plasma total homocysteine (tHcy). Methods. The levels of tHcy before and after oral methionine loading (ML) were measured in 135 healthy subjects and 39 patients scheduled for routine tHcy determination. The IMx method uses fluorescence polarization immunoassay (FPIA) technology. The HPLC-method includes derivatization with ABD-F and post-column fluorescence detection. Results. The imprecision was very low with both methods for both normal (11 μmol/L) and high (29 μmol/L) tHcy levels. The within and between-run coefficients of variation were < 5%. Both methods were able to discriminate between similar concentrations of tHcy both at normal and moderately high levels. There was a good correlation between measurements obtained with the two methods (r = 0.985, p = 0.001). The mean levels of tHcy measured with the IMx assay tended to be slightly higher than those with the HPLC both in the fasting state (mean difference = 0.8 μmol/L) and after ML (5.3 μmol/L). However only the difference in post-ML levels was statistically significant (p < 0.001). The percentage of patients with hyperhomocysteinemia identified with the two methods was similar. Interpretation and Conclusions. The IMx method compares well with an established HPLC method for measurement of fasting tHcy plasma levels
Tamoxifen reduces plasma homocysteine levels in healthy women
No full textTreatment with tamoxifen is associated with reduced incidence of myocardial infarction. As plasma homocysteine is an independent risk factor for cardiovascular disease, we studied the effects of tamoxifen on plasma homocysteine in 66 healthy women participating in the Italian prevention trial of breast cancer who were randomized in a double-blind manner to tamoxifen 20 mg day-1 or placebo for 5 years. They were aged between 35 and 70 years, had undergone previous hysterectomy for non-malignant conditions and had no contraindications to the use of tamoxifen. Plasma levels of total homocysteine (tHcy) were measured at randomization and after 2 and 6 months. The mean ± s.d. plasma levels of tHcy were 7.59 ± 1.71 μmol l-1, 7.25 ± 1.61 and 7.09 ± 1.33 in the tamoxifen group and 8.07 ± 2.06, 7.93 ± 1.77 and 8.12 ± 2.04 in the placebo group at 0, 2 and 6 months (P = 0.008 for the between-group difference over time). The higher the baseline tHcy level, the greater was the lowering effect of tamoxifen. No statistically significant effect of age, body mass index or smoking habit on baseline tHcy levels and its variation over time was found. In conclusion, tamoxifen (20 mg day-1 for 6 months) decreased plasma tHcy levels in healthy women. This effect may contribute to its protective effect on myocardial infarction
Effects of surgical stress and nitrous oxide anaesthesia on peri-operative plasma levels of total homocysteine - A randomised, controlled study in general surgery
No full textPrevious studies of patients have shown that anaesthesia with nitrous oxide (N2O) increases the plasma levels of total homocysteine. In a randomised, controlled trial we measured the plasma total homocysteine levels in patients undergoing general surgery before and after anaesthesia with and without N2O. Plasma total homocysteine levels were measured before anaesthesia and 1, 3-5 and 24 h after incision in 24 patients randomly allocated to anaesthesia with N2O (n = 12) and without N2O (n = 12). Total homocysteine levels significantly decreased from 10.4 +/- 2.7 to 8.2 +/- 2.9 mu mol.l(-1) in the non-N2O group 24 h after incision (p mol.l(-1) (p > 0.05). Our randomised controlled study indicates that total homocysteine decreases after general surgery in patients in whom anaesthesia is maintained without N2O, but not in patients in whom anaesthesia is maintained with N2O
Platelet aggregation studies : autologous platelet-poor plasma inhibits platelet aggregation when added to platelet-rich plasma to normalize platelet count
No full textAdjusting platelet count (PC) in platelet-rich plasma (PRP) using platelet-poor plasma
(PPP) is recommended for platelet aggregation (PA) studies, but it could also affect
PA independently of the decrease in PC. Analysis of aggregation tracings from healthy
controls showed that PC correlated with PA in 47 diluted-PRPs, but not in 104 undiluted-
PRPs. Dilution of 9 PRPs with PPP progressively decreased PA, while dilution of
washed platelets with buffer hardly affected PA. Apyrase partially prevented the
inhibitory effect of PPP. Therefore, the practice of diluting PRP with PPP to adjust
platelet count should be avoided because it artefactually inhibits P
Low vitamin B(6) plasma levels, a risk factor for thrombosis, in inflammatory bowel disease: role of inflammation and correlation with acute phase reactants
No full textOBJECTIVES: Individuals with inflammatory bowel disease (IBD) are at increased risk for thrombosis and vitamin deficiencies. Low plasma levels of vitamin B6 are an independent risk factor for thrombosis and may cause hyperhomocysteinemia, another recognized risk factor for thrombosis. The aim of this study was to evaluate vitamin B6 plasma levels in IBD patients. METHODS: We studied 61 IBD patients: 32 with Crohn's disease and 29 with ulcerative colitis. For each patient, three sex- and age-matched healthy control subjects were studied. RESULTS: Median vitamin B6 levels were significantly lower in IBD patients (22.0 pmol/L, range 3.6 -231.0) than in controls (31.1 pmol/L, 3.7-363.4; p < 0.01). In all, 13.1% IBD patients and 5.5% controls had plasma vitamin B6 levels lower than the 5th percentile of distribution in normal controls (p < 0.05). Low vitamin B6 levels were significantly more frequent in patients with active disease than in patients with quiescent disease (seven of 26, 26.9%, vs one of 35, 2.9%; p < 0.001). Moreover, patients with active disease had significantly lower median vitamin B6 levels (13.4 pmol/L, range 3.6-124.0) than patients in a quiescent phase (27.0 pmol/L, 7.8-231.0; p < 0.001). Low vitamin B6 levels were significantly correlated with serum concentrations of C-reactive protein (r = -0.36, 95% CI = -0.59 to -0.09, p < 0.01) and α1-acid-glycoprotein (r = -0.37, 95% CI = -0.59 to -0.10, p < 0.01). Hyperhomocysteinemia was more frequent in patients with low vitamin B6 levels (three of eight, 37.5%) than in patients with normal levels (nine of 53, 17.0%; p = 0.18). There was no statistically significant correlation between vitamin B6 and homocysteine plasma levels (r = -0.13, 95% CI = -0.37 to +0.14, p = 0.33). CONCLUSIONS: Low vitamin B6 plasma levels, an independent risk factor for thrombosis, are frequent in patients with IBD, especially those with active disease
Evaluation of the abnormal platelet function in von Willebrand disease by the blood filtration test
No full textWe have evaluated platelet function in different subtypes of von Willebrand disease (vWD) by pushing blood through the capillary-sized channels of a glass filter. Patients, including those with type IIB vWD, showed lower than normal platelet retention and increased cumulative number of blood drops passing through the filter as a function of time. In contrast, shear-induced platelet aggregation, measured in the cone-and-plate viscometer, was paradoxically increased in type IIB patients. Treatment with 1-desamino-8-D-arginine vasopressin (DDAVP) tended to normalize the filter test in patients with type I-platelet normal and type I-platelet low vWD, but infusion of a factor VIII/von Willebrand factor (vWF) concentrate lacking the largest vWF multimers was without effect in type 3 patients. Experiments with specific monoclonal antibodies demonstrated that the A1 and A3 domains of vWF, as well as the glycoproteins Ibα and IIb-IIIa on platelets, are required for platelet retention in the filter. Thus, the test may reflect vWF function with regard to both platelet adhesion and aggregation under high shear stress, and provide relevant information on mechanisms involved in primary hemostasis
Evaluation of platelet function with the PFA-100 system in patients with congenital defects of platelet secretion
No full textThe template bleeding time is still the screening test for defects of platelet function, although it is an invasive and poorly reproducible technique. The PFA-100 measures platelet function at high shear. Whole blood is aspirated through a capillary to an aperture of a membrane coated with platelet agonists. The system measures the time required to obtain occlusion of the aperture by a platelet plug (closure time). We measured the closure times in the PFA-100 system and the bleeding time in seven patients with δ-storage pool deficiency, 10 patients with 'primary secretion defect' (not due to abnormalities of platelet granules or the arachidonate pathway), and 40 controls. Measurements were repeated 1 and 4 hours after intravenous infusion of desmopressin in six δ-storage pool deficiency and eight primary secretion defect patients. Baseline bleeding time and closure times with the collagen/epinephrine cartridge were longer in δ-storage pool deficiency and primary secretion defect patients than in controls. In contrast, closure times with the collagen/adenosine diphosphate cartridge were normal in both δ-storage pool deficiency and primary secretion defect patients. Treatment with desmopressin increased the plasma von Willebrand Factor levels, shortened the prolonged bleeding time, shortened the closure times with the collagen/adenosine diphosphate cartridge, and normalized the closure times with the collagen/epinephrine cartridge. Therefore, the PFA-100 test may be a less invasive alternative to the bleeding time in the diagnosis and therapeutic monitoring of patients with platelet secretion defects. The collagen/epinephrine cartridge is more sensitive than the collagen/adenosine diphosphate cartridge to defects of platelet secretion. Copyright (C) 1999 Elsevier Science Ltd
High prevalence of hyperchomocysteinemia in patients with inflammatory bowel disease: a pathogenic link with thromboembolic complications?
No full textWhy patients with inflammatory bowel disease are at increased risk for thrombosis is unknown. Since they may have impaired absorption of vitamins that regulate the metabolism of homocysteine, we tested the hypothesis that they have hyperhomocysteinemia, an established risk factor for arterial and venous thrombosis
