Preliminary study of stability of blood used in the one tube osmotic fragility test to screen severe thalassemia carriers

At present, one-tube osmotic fragility test (OFT) is used to screen severe thalassemia carriers. This study was aimed to study of stability of blood used in the osmotic fragility test (OFT). One hundred and fourteen EDTA blood samples were recruited, comprising 8 β-thalassemia carriers, 2 α-thalassemia 1 (SEA deletion) carriers, 19 hemoglobin E carriers (Hb E), 1 homozygous HbE (Hb EE), 1 hemoglobin constant spring (HbCS) carrier and 83 normal. Blood samples were stored at 4 oC throughout the study. All blood samples were tested for OFT at 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 48, 72, 96 and 120 hours, respectively, by using the KKU-OF test. The results showed that the stability of blood samples from β-thalassemia, α-thalassemia 1 (SEA deletion) and homozygous HbE was 36, 32 and up to 120 hours, respectively, whereas that of Hb E heterozygote was 16 hours. The remaining groups were negative at 0 hour and remained negative throughout the study. This study suggested that one-tube OF test (OFT) can be used to screen two types of severe thalassemia carriers (β-thalassemia, α-thalassemia 1) effectively but it is not applicable for HbE heterozygote and Hb CS screening. The screening accuracy depended on preservation period of blood samples. To obtain maximal accuracy, the blood samples should be tested within 32 hours after collection. The knowledge generated from the present report would be great benefit for the national thalassemia prevention and control program. Bull Chiang Mai Assoc Med Sci 2008; 41: 94-102.