Comparative estimation of the value of monocompartmental methods of analyzing /sup 99m/Tc-DTPA slope clearance with special attention to long examination times

Plasma slope clearance estimation with /sup 99m/Tc-DTPA corresponds to total clearance determination. When activity is measured directly in cumulative serum samles, determination of the plasma slope clearance is suitable for practical applications only if simplified analytic procedures are used. Monocompartmental analytic procedures that take into account the late slope of the disappearance curve are particularly useful for glomerular filtration rate estimation. The A3k3-slope-clearance analysis method is a monocompartmental procedure for determining slope clearance that is based on activity measurements between the 100th (120th) and 240th minute after injection. Compared with other monocompartmental procedures, the A3k3-slope-clearance method shows a highly significant hyperbolic correlation with serum creatinine, a highly significant linear correlation with inulin total clearance, is age dependent and yields reproducible results. The sensitivity (frequency of correct function results in the case of disturbed glomerular function) of the A3k3-slope-clearance method with /sup 99m/Tc-DTPA is particularly good. The practically important predictivity of pathological A3k3-clearance results (frequency of correct results when the kidney function is truly reduced) is on the average 85%. The mean efficiency of the method is 88% (65-97% at the 95% confidence level). (author)