Fetal Red Cell in Thai Thalassemia Trait Patients

Suntaree Apibal, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Bangkok 10400 (Thailand) The presence of fetal red cells (F cells) in the maternal circulation is an indicator of a fetomaternal hemorrhage which may subsequently lead to hemo-lytic disease of the newborn [1]. However, a small amount of F cells were found in some normal adults [4] whereas the increase in hemoglobin F production might be increased in various conditions as thalassemia trait, unstable B chain variant and pregnancy [4]. In Thailand, thalassemia hemoglobin E-trait, ß-trait and α-trait were commonly found [2, 3]. The incidence of E-trait is 13% on average in the central region, 40% in the northeast, 8% in the north and 12% in the south [2]. The incidence of ß-trait is 3–9% and of α-trait is 20–30% [3]. So, the study for the percentage of F cells among these groups of subjects may be able to differentiate the false positive results of fetomaternal hemorrhage from F cells found in some normal persons and subjects with the thalassemia trait. F cells could be demonstrated in the maternal circulation by acid elution techniques. Our study revealed the presence of F cells in each group by the Saquan-sermsri acid elution technique as follows. The air-dried blood smear of not over 24 h was fixed in 80% ethanol for 3 min, then immersed in acid/alcohol/ami-do black solution for 3 min at room temperature (100 mg amido black B CI No. 20470, Merck’s Reagenzien, FRG, in 100 ml of 80% ethanol, pH adjusted to 2 with HC1). The smear was washed with tap water for 15 s and air dried. The stained smear was examined under an oil immersion microscope. The percentage of F cells (X ± SD) in 30 normal persons, 30 with E-trait, 30 with ß-trait and 30 with α-trait were 0.14 ± 0.18, 0.92 ± 0.78, 2.3 ± 1.87, and 0.5 ± 0.45, respectively. So, more investigations to exclude these conditions were needed before diagnosing fetomaternal hemorrhage. Thus, the diagnosis of fetomaternal hemorrhage is only valid in the presence of F cells in the maternal circulation if there are no such hemoglobinopathies in the mother. References Fanaroff AA, Martin RJ, Merleatz IR: Behrman’s Neonatal Perinatal Medicine, Disease of the Fetus and Infant, ed 3. St. Louis, Mosby, 1983. Na-Nakorn S, Minnich V, Chernoff A: Studies on hemoglobin E. II. The incidence of hemoglobin E in Thailand. J Lab Clin Med 1965;47:490. Wasi P, Na-Nakorn S, Pootrakul S, Sookanek M, Disthasong-chan P, Pornpatkul M, Panich V: Alpha and beta thalassemia in Thailand. Ann NY Acad Sci 1969;165:60.