Calculated Estimates of Plasma Volume in Patients With Chronic Heart Failure—Comparison With Measured Volumes

•Formula-derived estimates of plasma volume (PV) show poor correlation with quantitative measurements.•Calculated estimates of PV should be considered cautiously to guide volume management.•Quantitative measurements of PV provide “gold standard” accurate assessments.•More work is needed to make calculated values more accurate indicators of volume. Calculated estimates of plasma volume (PV) have been developed with the use of hemoglobin/hematocrit-body weight–based methods. The accuracy of such formula-derived values has not been thoroughly evaluated. The objective of this analysis was to compare the calculated estimate and a quantitative measure of PV in patients with chronic heart failure (HF). PV was measured with the use of a standardized computer-based indicator-dilution–labeled albumin technique in 110 patients with clinically stable chronic HF and correlated with paired Kaplan-Hakim (K-H) and Strauss formula estimates of PV. The K-H formula underestimated (3.4 ± 0.7 L) and the Strauss formula overestimated (5.3 ± 1.5 L) PV relative to the measured volume (4.3 ± 1.1 L). Calculated PV was only moderately correlated with measured PV by the K-H formula (r = 0.64; P < .001) and weakly by the Strauss formula (r = 0.285; P = .003). Strauss formula estimates of change (%) in PV were also poorly correlated with paired measured changes in PV (r = 0.162; P = .999; n = 40). Calculated estimates of PV demonstrate limited association with measured volumes. These findings indicate that although formula-based estimates of PV have been shown to have prognostic value, they are limited in their reliability for volume management in patients with chronic HF.