A rapid diagnostic test for sickle cell anemia.

S ICKLE cell anemia is a congenital chronic hemolytic type of anemia characterized hematologically by the development of oat-shaped and sickle-shaped erythrocytes. Other cellular abnormalities which are due to excessive blood de-’ struction and active blood formation are also seen in blood smears. Six to IO per cent of Negroes possess the sickle trait 2p 3; their red blood cells have the capacity to sickle, but most of these individuals do not develop anemia. The course of the sickling process as observed under the microscope has been described in detail by several investigators, 4* j* 6* lo but little is known about the physical processes involved in sickling. It has been established, however, that the erythrocytes of individuals with sickle cell anemia and sickle cell trait become sickled when the hemoglobin is reduced. 8* I4 When the hemoglobin is combined with oxygen or carbon monoxide, the cells are indistinguishable in form from normal erythrocytes. The term promeniscocyte has been applied to the latter form and meniscocyte to the former. l1 Hahn and Gillespie8 and Sherman’” obtained sickling physically by reducing the partial pressure of oxygen over suspensions of promeniscocytes. They were able to reverse the process by passing oxygen or carbon monoxide over meniscocytes. When oxygen is removed from promeniscocytes, their hemoglobin aggregates in one or more foci within the cells, and the cell membrane collapses. When oxygen is ‘added to these cells, they resume their normal contour, and hemoglobin appears to be distributed uniformly throughout their interior. Meniscocytes are strongly birefringent under the polarizing microscope14 while promeniscocytes are not. When a drop of blood is sealed between a cover slip and a slide, the decline in oxygen tension due to oxidative processes in the blood cells leads to sickling.’ This is the common diagnostic test for sickle cell anemia and sickle cell trait used in clinical laboratories. Sherman found that increase in temperature, high leukocyte count, and bacterial contamination, all of which increase the rate of oxygen consumption, accelerated the sickling process. In another method, a saline citrate suspension of blood is allowed to stand in a test tube under a layer of paraffin oil until sickling takes place.’ In employing any of the common diagnostic tests for sickling it is desirable to obtain blood which has a low.fraction of oxyhemoglobin. Thus, the moist stasis method, l3 in which blood is obtained from a patient’s finger after its circulation has been occluded for five minutes, gives the most rapid and consistent results. Even with this method it is sometimes necessary to observe the preparation for several hours before the result is conclusive.5 In order to find a more convenient and rapid method of produing meniscocytes