INFLUENCE OF FRESHNESS OF EDTA BLOOD ON RELIABILITY OF THALASSEMIA SCREENING TESTS

Thalassemia screening tests include one tube (0.36% NaCl) osmotic fragility test (OFT), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH). Reliability of these parameters in stored EDTA blood is the important issue to be concerned. To address this issue, we analyzed the results of these thalassemia screening tests in 50 fresh and stored EDTA blood samples of collected in the Chiang Mai province of northern Thailand. These blood samples; 25 with MCV < 80 fl and 25 with MCV ≥ 80 fl, were stored at room temperature (RT) (approximately 30°C) and in cold (approximately 4°C). OFT, MCV, and MCH were tested in both groups of blood samples everyday for 7 days. It was found that falsely negative OFT results were seen after 1 day and 4 days of storage at RT and in cold, respectively. For MCV, acceptable values were obtained at 0 day and 2-3 days storage at RT and in cold, respectively. No change of MCH values was observed throughout 7-day storage at both RT and cold. It was concluded that when performing thalassemia screening tests in Thailand, fresh EDTA blood must be used for OFT test and MCV determination. However, although MCH seemed to be the most stable parameters, thalassemia screen cannot rely only on MCH value. Therefore, thalassemia screen using these three tests must be done within blood collection day if no cooling facility is available. This information would also be useful for countries in tropical region where ambient temperature is high.