A comparison of direct and extraction methods for the determination of T-1824 (Evans blue) in plasma and serum.

The dye T-1824 (Evans Blue) has gained wide acceptance for determining plasma volume. Recently there has been a renewed interest in dye circulation studies for the measurement of cardiac output, central volume, cardiac shunts, and valvular regurgitation. The method of estimation most commonly used is spectrophotometric analysis of the dye-tinged plasma (or serum) compared with standard dye solutions prepared from the subject's plasma using a plasma blank (Chinard, 1951). Haemolysis and lipaemia introduce serious errors in these determinations (Gregersen, 1938). To overcome these factors, sex eral extraction methods have been described (e.g., Allen, 1951; Bedwell, Patterson, and Swale, 1955). To our knowledge no studies have been made on the relative values in routine clinical investigation of extraction and direct measurement of the dye in plasma (or serum). The purpose of this paper is to compare an acetone-extraction method with direct estimation in plasma and serum and to discuss their relative merits in clinical use.