[Simple and rapid method for the fractionation of red blood cells in sickle cell anemia]

The density of normal red blood cells increases during their 3-month life span. This characteristic has been used for many years to separate younger from older cells by centrifugation, allowing biochemical and physiological studies on the ageing process in red cells to be performed. The methods which have been proposed to date using discontinuous density gradients made of high density chemical compounds required high speed centrifugation of long duration. These gradients with pre-established density layers are well designed to separate red cells when their density varies over a small range as in blood from healthy donors. Pathological red cells such as found in sickle cell anaemia, thalassaemia syndromes or haemolytic anaemia of various origins display a wide and unpredictable range of densities which precludes the use of a standard discontinuous gradient. Because the fractionation of such pathological blood specimens is of great clinical and biochemical interest we report the details of a new method which combines two steps: firstly and analytical method performed with phthalate esters which allows estimation of the distribution of particular red cells, secondly a preparative method using Percoll solutions to prepare the discontinuous density gradient according to the histogram given by the first step. Two examples are described illustrating this interesting method which may possibly be applied to other blood disorders.