Determination of Red-Cell Volume with a Nonradioactive Marker (Sodium Fluorescein) in Humans Using Flow Cytometry

Abstract

<i>Objective: </i>To evaluate a method to measure red-cell volume (RCV) using a nonradioactive marker (sodium fluorescein) and flow cytometry. <i>Design: </i>Study of reproducibility and feasibility of the method in healthy volunteers. <i>Setting: </i>Laboratory of an intensive care unit at a university hospital. <i>Participants: </i>Five healthy male and 10 healthy female subjects. <i>Interventions: </i>A total of 28 RCV determinations was carried out in the 5 male subjects to establish the reproducibility of the method. Twenty of the RCV determinations were performed as duplicate measurements (interval: 1 h). The longest period between two subsequent measurements was 112 days. In the 10 female subjects a total of 20 RCV determinations was carried out (two measurements per subject with a 1-hour interval. <i>Results: </i>The variation coefficient (mean ± standard deviation) in male subjects was 3.1 + 1.4%. The mean differences ( ± SD) between the measurements carried out on different days and those carried out as duplicate measurements on the same day did not differ (0.0 + 3.8% versus 0.6 + 4.7%). RCV in relation to body weight and body surface area, respectively, was 29.1 ± 2.7 ml/kg and 1,108 ± 90 ml/m<sup>2</sup> in males and 24.0 ± 1.5 ml/kg and 848 ± 56 ml/m<sup>2</sup> in females. <i>Conclusions: </i>We conclude that sodium fluorescein is a suitable nonradioactive marker for RCV determination and that RCV is constant over long periods of time.