A variety of methods have been proposed to estimate the glomerular filtration rate (GFR) from the renal uptake of technetium Tc 99m-DTPA using a gamma camera. To compare alternative methods, we calculated the GFR in several different ways from measurements in 33 patients and compared the results with an independent GFR measurement based on eight-point plasma clearance of ytterbium Yb 169-DTPA. The best agreement was obtained using an algorithm that has not been described previously, in which correction was made for overlap of the kidneys by the liver and spleen. The correlation coefficient was 0.958, and the residual standard deviation was 12.1 ml/min. This method required a single 20-min blood sample as well as the camera data. The best method not requiring a blood sample was significantly less accurate, with a correlation coefficient of 0.837 and a residual standard deviation of 23.1 ml/min. The accuracy of these methods was comparable to that reported for creatinine clearance, the most commonly used estimate of the GFR in current clinical practice.

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Details of a series of computer programs associated with a complex renal function procedure, all linked together into a single "macrofunction" are presented. Input consisted of not only in vivo nuclear medicine information, but also data concerning patient identification, urine volumes, voiding time, urine specific gravity, blood pressure and other pertinent information. Computer output consisted of images, curves and typed information presented in an integrated format ready for inclusion into the patient's record. Clinical evaluation of this comprehensive renal function macrofunction has proved to be useful, econominal, rapid and accurate. It has conveniently sorted a wide variety of disease states and provided clinical information not available from any other non-invasive technique.