Abstract: A screening test for beta-thalassemia trait carriers is carried out by mixing 10 .mu.l of blood of the patient with 2 ml of an aqueous solution prepared from glycerol, sodium chloride, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium azide, Acid Green 5 to obtain a suspension. A well cluster, having several wells is used. The suspension is formed in one well and the turbidity is determined by placing a reading scale under the cluster.