Simplified method for the long-term study of turnover and body masses of cholesterol by input-output analysis

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Abstract
A simplified, labor-saving procedure is proposed for the long-term follow-up of plasma cholesterol specific activity decay curves, using computerized input-output analysis. During the initial 2 weeks after tracer injection, frequent (4 to 6 or more) blood samples are obtained. For the following 40 weeks blood is taken only once a month. During the last 4 weeks of the experiment, blood samples are obtained weekly or twice weekly (method A). Seventeen patients were studied for 50 to 66 weeks. When the computer used data points obtained only every fourth week (in the midsection of the curves), the mean error incurred in the parameters of the analysis (compared to the full analysis of weekly data points) were: IT (sum of absorbed dietary and biosynthesized cholesterol); 2.6% smaller; Ma (rapidly exchangeable mass of cholesterol): unchanged; M (minimum value for total exchangeable mass of cholesterol): 5.9% smaller: M-Ma (remaining mass of cholesterol): 9.5% smaller. Another simplified method (method B) consists of weekly follow-up of the decay of specific activity for the initial 12 weeks after tracer injection. During the following (circa) 30 weeks no blood samples are obtained. At the end of this period weekly or twice weekly blood specimens are obtained for 4 weeks. When the results of this procedure were compared to full curve analyses the mean differences were: IT: 2.1% smaller; Ma: unchanged; M: 9.3% smaller; M-Ma: 14.9% smaller.