Electrical impedance assays of blood cells

In this review, the capability of electrical impedance spectroscopy analysis of blood cells, especially for red blood cells is presented, highlighting its large area of related biomedical relevance. The method is briefly introduced and basic theoretical aspects are discussed by considering both phenomenological (e.g. equivalent circuit) and microscopic approaches. The latter include a comparative analysis of the relevance of considering real shape (consistent with microscopic observations) versus spheroidal approximations (prolate and oblate spheroids) with the same surface and volume concentration. We show that while ellipsoidal approximation is fairly good for randomly oriented cells, it is quite poor whenever oriented cells are measured. The voluminous literature on the electrical analysis of blood cells is reviewed to stress the most promising biomedical applications of the method either per se or in combination with complementary e.g. (micro) fluidic approaches.