Biomedical subjects
C Flavell
Publications and source records attributed to C Flavell.
A validation study comparing accelerator MS and liquid scintillation counting for analysis of 14C-labelled drugs in plasma, urine and faecal extracts.
A comparison has been made between accelerator mass spectrometry (AMS) analysis and liquid scintillation counting (LSC) of plasma, urine and faecal samples containing 14C-labelled drugs. In an in vitro study in which human plasma was spiked (the term spiked is used in Section 2.6) with 14C-Fluconazole (14C-FL) over a concentration range of 0.1-2.5 dpm/ml, a correlation coefficient of 0.999 was determined for AMS analysis versus extrapolated LSC data. No significant day to day (or inter-day)variation was seen (P < 0.05 by ANOVA). Coefficients of variation for these analyses ranged from 2.68 to 6.50%. In vivo studies in which rats were given a high (11.5 microCi/kg) or low (18.1 nCi/kg) radioactive dose (to model an exposure of 0.9 microSievert to man) of 14C-Fluticasone propionate(14C-FP) showed that there was also a good correspondence between AMS and LSC data. A mass balance study in a single the faeces by 96 h; less than 1% of the administered dose was excreted in the urine. The limit of reliable measurement of drug related material, above background concentrations, by AMS analysis in this study was approximately 0.1 dpm/ml for plasma, 0.01 dpm/ml for urine without any sample extraction or concentration and 0.01 dpm/ml for faecal extracts. The data reported here demonstrate that AMS is an ultrasensitive and reliable method for analysing 14C-labelled drugs in human and animal body fluids.
Relationship between right and left-sided filling pressures in 1000 patients with advanced heart failure.
BACKGROUND: Elevated left ventricular filling pressures present a major target of therapy for symptomatic heart failure but are difficult to assess directly. Because the relationship of left- and right-sided pressures remains ill defined in chronic heart failure, this study compared 3 right-sided measurements (right atrial [RA] pressure, pulmonary artery systolic [PAS] pressure, and severity of tricuspid regurgitation [TR]) to the pulmonary capillary wedge (PCW) pressure. METHODS: Hemodynamic measurements and echocardiography were available from 1000 patients undergoing transplant evaluation. Right atrial and PAS pressure, and TR severity were compared to PCW pressure. For 754 patients undergoing repeat measurements, changes in RA and PAS pressures were compared to PCW changes. RESULTS: Right atrial pressure correlated with PCW pressure (r = 0.64), regardless of etiology or TR severity. Right atrial pressure changes correlated with PCW changes (r = 0.62). Discordance was defined as either RA > or = 10 mm Hg despite PCW < 22 mm Hg (6%) or RA < 10 mm Hg despite PCW > or = 22 mm Hg (15%). For detection of PCW > or = 22 mm Hg, positive predictive values were 88% for RA > or = 10 mm Hg, 95% for PAS > or = 60 mm Hg, and 79% for > or = moderate TR. Pulmonary artery systolic pressure correlated very closely with PCW (r = 0.79), and could be estimated as 2 x PCW. Reduction in PAS pressure during therapy was strongly determined by PCW pressure reduction (r = 0.67). CONCLUSIONS: Accurate estimation of RA pressure can potentially guide therapy of left ventricular filling pressures in approximately 80% of chronic heart failure patients without obvious non-cardiac disease. In this population, elevated PAS pressures are largely determined by elevated left-sided filling pressures.