PubMed · 16138484
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Trevor Baglin. Acquired bleeding disorders.. https://doi.org/10.7861/clinmedicine.5-4-326
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PURPOSE: Measurements of cytokine release in whole blood after ex vivo stimulation are useful in drug development. The components contributing to variation within such assays have not been clearly defined. Therefore, we characterized the sources of variability within an ex vivo stimulation assay for TNF-alpha release. METHOD: Fresh whole blood or mononuclear cells from a cell preparation tube were added to silanized, screw-top tubes with a final concentration of 1 microg/mL lipopolysaccharide (LPS). Each tube was purged with 95% air/5%CO2 and incubated 4 or 6 h at 37 degrees C in a metabolic water bath. Plasma TNF-alpha was next measured in supernatants by immunoassay. Total method variability was assessed in 10 normal donors each drawn in the morning and afternoon over 3 days. Four additional samples were pre-treated with dexamethasone to investigate inhibition of TNF-alpha release. RESULTS: Our analysis indicated precise temperature control, the timing and duration of stimulation, and the surface properties of the stimulation vessel most significantly influenced assay performance. A comparison of multiple anticoagulants indicated that careful consideration should be taken in selecting the optimal anticoagulant. The estimated total assay CV for all anticoagulants tested was less than 33.81%. The analytical variability (stimulation and measurement) was less than 25.88% CV. The one exception was mononuclear cells collected in sodium heparin. The total variability estimate incorporated day-to-day, diurnal, inter-donor, tube-to-tube and immunoassay variability. Using our optimized conditions, TNF-alpha release was inhibited by dexamethasone with a mean IC50 of 33.3 +/- 4.6 nM. CONCLUSIONS: We have described an optimal set of conditions for collection, storage and processing of an ex vivo cytokine stimulation assay. These conditions were selected for operational feasibility, minimal imprecision and elimination of potential confounding factors. The end result is a more robust method that can be applied to clinical drug development.
This study describes a generic biological screening assay designed to detect anticoagulant rodenticides based on their inhibitory action on the vitamin K epoxide reductase protein complex, resulting in an accumulation of under-carboxylated prothrombin or proteins induced by vitamin K antagonism (PIVKA-II). A combined cell culture/ELISA assay was optimized to measure PIVKA-II production by the human hepatoma HepG2 cell line cultured in the presence of anticoagulant rodenticides. The specificity and sensitivity of the assay was validated using 41 grain extracts containing representative concentrations of rodenticide or appropriate nonrodenticide control compounds. In all cases, PIVKA-II produced by HepG2 cells in response to grain extracts spiked with rodenticides was detected by ELISA, while PIVKA-II was not detected in supernatants collected from cells exposed to nonrodenticide controls. This represents a novel, class-specific biological assay for the detection of anticoagulant rodenticides present in contaminated grain.
BACKGROUND: Patients taking oral anticoagulants with an international normalized ratio (INR) greater than 4.0 are at increased risk for bleeding. We performed a meta-analysis to determine the effectiveness of phytonadione (vitamin K) in treating excessive anticoagulation. METHODS: The MEDLINE, EMBASE, and Cochrane Library databases were searched (without language restrictions) for articles published between January 1985 and September 2004. Randomized controlled trials or prospective, nonrandomized trials that used vitamin K to treat patients without major hemorrhage with an INR greater than 4.0 due to oral anticoagulant use were included. The primary outcome was achievement of the target INR (1.8-4.0) at 24 hours after vitamin K administration. Summary estimates were calculated using a random effects model. RESULTS: Twenty-one studies (10 randomized and 11 prospective trials) were included. Among oral vitamin K treatment arms (4, n = 75), the proportion with a target INR at 24 hours was 82% (95% confidence interval [CI], 70%-93%), which was similar to intravenous vitamin K treatment arms (6, n = 69; target INR, 77%; 95% CI, 60%-95%). Treatment arms of subcutaneous vitamin K (3, n = 58; 31%; 95% CI, 7%-55%) and placebo/observation (2, n = 27; 20%; 95% CI, 0%-47%) were less likely to achieve target INR at 24 hours. Only 1 of 21 trials appropriately assessed for adverse events, so a summary estimate for bleeding risk could not be generated. CONCLUSIONS: Limited evidence suggests that oral and intravenous vitamin K are equivalent and more effective for excessive anticoagulation than simply withholding warfarin sodium. Subcutaneous vitamin K, however, is inferior to oral and intravenous vitamin K for this indication and is similar to placebo. Whether treatment with vitamin K decreases hemorrhagic events cannot be determined from the published literature.