Category: clover review

Sex-specific tertile cutoffs was in line with the varying withdrawals about control subjects

Sex-specific tertile cutoffs was in line with the varying withdrawals about control subjects

Blood testing and analyses

Samples in the VIP were collected in the morning, and only 12 of 825 study subjects (1.5%) had fasted <4 hours, and 146 (18%) <8 hours. In the MSP, blood samples were collected throughout the day, and 163 of 168 study subjects (97%) had fasted for less than 4 hours. The blood samples used in the present study were collected in EDTA sample tubes, separated into plasma, buffy coat, and erythrocyte fractions, aliquoted, and cryopreserved at ?80°C. Samples are frozen within 1 hour of collection, either at ?80°C or at ?20°C for up to 1 week before transfer to a ?80°C freezer at the Northern Sweden Medical Biobank for long-term storage. All biochemical analyses were performed at Bevital AS, Bergen, Norway (27). Folate and cobalamin concentrations were determined with a microbiologic method, using Lactobacillus casei for folate and Lactobacillus leichmannii for cobalamin, adapted to a microtiter plate format, and carried out by a robotic workstation. Concentrations of total homocysteine were measured with an isotope dilution gas chromatography–mass spectrometry method (28). Concentration of methionine sulfoxide was determined using a liquid chromatography-tandem mass spectrometry method. The coefficients of variation for serum folate and cobalamin are 5%, whereas the coefficients of variations for homocysteine and methionine/methionine sulfoxide are <5% (29). The investigators and laboratory staff were blinded to case and control status.

Analytical analyses

Mann–Whitney and ? 2 tests were used to compare baseline characteristics and study variables in cases and controls. Odds ratios (OR) for disease and 95% confidence intervals (CI) were calculated by conditional logistic regression. In this report, plasma metabolite tertiles were used instead of quintiles, used in our previous report, to preserve power in subgroup analyses. Results for quintiles are available in Supplementary Table S1 (9). Because cases and controls were matched by cohort, tertile cutoffs were not stratified for cohort. Tests for trend were performed by including tertiles (labeled with sex-specific tertile medians) as continuous variables in regression analyses. Covariates for the multivariate analysis were selected to reproduce the procedure of our previous study (9). Variables included were body mass index (BMI; <25, 25–30, and >30 kg/m ?2 ), smoking (current, not current smoker), intake of alcohol (sex-specific quartiles), and recreational and occupational physical activity (self-reported on a scale from 1 to 5). Continue reading “Sex-specific tertile cutoffs was in line with the varying withdrawals about control subjects”