In a previous study of 201 healthy men (1), red cell volume (Vrbc) was measured by a modification of Sterling and Gray's radiochromium method (2), and whole blood and plasma volumes (Vwb and Vpl) were derived from venous hemiatocrits. The influence of factors other than body size on the variance of the data was studied, and standards for predicting normal volumes were derived. The present report describes a similar examination of 101 women.
SUBJECTS AND METHODSThe women, all of whom volunteered for study, were actively employed as housewives, laboratory personnel, nurses, or office workers, and most were white (Table I) tResearch Fellow, American Heart Association. prevent venous congestion during sampling. Hematocrit readings were not corrected for plasma trapping, and it was assumed that Vwb = VCr"1 (no allowance was made for a difference between the hematocrit of venous blood and that of the body as a whole) (1). Cell and plasma volumes were calculated by the formulas: Vrhc = VCr`1 X hematocrit; Vpl = VCr5`-Vrbc.The data were treated as outlined in the study of men (1). Regression equations were calculated by the method of least squares to describe the relations between volumes (Vrbc, Vpl, and Vwb) and body measurements (weight, height, weight and height combined, and surface area). The differences between the observed volumes (Vrbc and Vpl) of each woman and the mean volumes found in women of the same height and weight vere calculated by means of Equations 3 and 7, Table II. These differences, or "residuals," wsere used to analyze the influence of factors other than body size On the blood volumes. Table I summarizes the data. In Figure 1, each of the 101 subjects is represented according to her weight and height. In general, the relationship between weight and height was fairly uniform. Notable exceptions were four women weighing over 81 kg, who proved to be 23 to 58 per cent overweight for height and age according to actuarial tables (5). The weight: height ratios of these subjects were more than 2 standard deviations above the mean of the ratios of the other 97 women. For this reason and because the series included so few large women, regression equations describing the relationships of the volumes to body measurements were prepared only for the 97 women weighing less than 74 kg (Table II).
RESULTS
Volumes in relation to height and weightThe bivariate regression equations described straight lines and the trivariate equations, planes without curvature (see Figures 1 to 4). The location of the regression plane for Vrbc in rela-2182
To evaluate the informational value of renal biopsy in nephritis of systemic lupus erythematosus, we selected the records of 30 patients who had a renal biopsy done and also had a known clinical outcome. Detailed case histories were prepared, and three distinct randomly chosen cases were given to 197 academic rheumatologists. The rheumatologists estimated the probability of future clinical events (worsened serum creatinine, worsened urine protein, renal death, and aggressive therapy) at 3 and 12 months after the biopsy. Biopsy results were given in detail, and probability estimates were made of the same clinical events using the additional information. The accuracy of each probability estimate was measured using a scoring function that depends on the estimates and the actual outcomes. Knowledge of the renal biopsy failed to improve predictive accuracy scores of estimates of future serum creatinine levels, urine protein levels, and renal death at 3 and 12 months (p less than 0.0001), and for estimates of the probability of the use of aggressive therapy at 12 months (p less than 0.007). The renal biopsy information improved only the accuracy of predictions concerning the use of aggressive therapy at 3 months (p less than or equal to 0.0003). Knowledge of the renal biopsy results failed to add important prognostic information about the future course of treated lupus nephritis to information already obtained from history, physical examination, and laboratory tests.
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