A Simplified Screening for α-Thalassemia 1 (SEA Type) Using a Combination of a Modified Osmotic Fragility Test and a Direct PCR on Whole Blood Cell Lysates

Abstract

In order to provide a rapid method for identifying α-thalassemia 1 in a region with massive population and limited resources, we have tested a rapid screening strategy. Preliminary screening was done using a modified onetube osmotic fragility test (OF test) followed by RBC indices; Hb analysis and detection of α-thalassemia 1 with the Southeast Asian deletion (SEA type) were performed by PCR. One hundred and seventy-five adult Thai subjects were studied. Fifty-one of the 175 subjects (29.1%) were positive for a modified OF test. They all had significantly lower MCV and MCH but higher RDW-CV values as compared to the OF negative group. A successful identification of α-thalassemia 1 deletion using a direct PCR on cell lysates was demonstrated. Among the 51 OF-test-positive subjects, 7 were found to be α-thalassemia 1 carriers, 3 of whom were also carriers of Hb E. No α-thalassemia 1 was detected in the OF-test-negative group. A combination of a modified OF test and a direct PCR analysis on whole blood cell lysates would therefore provide an effective screening for α-thalassemia 1 in the regions where a program of prevention and control of the disease remains underserved.

Evaluation of single‐tube osmotic fragility as a screening test for thalassemia

“…The one-tube osmotic fragility test may be positive in the presence of hemoglobin E, and this can be useful [1,3,5]. However, our results confirm that this cannot be relied on so that an alternative strategy is needed for the detection of this variant hemoglobin in South East Asian populations.…”

“…In one direct comparison, a 0.36% solution provided a more sensitive test but was less specific than a 0.32% solution [3]. The use of a 0.34% solution has been recommended when the test is intended as a screening test for a 0 thalassemia, with detection of all examples of b thalassemia trait also being reported in this study [5]. Iron deficiency anemia is a recognized cause of falsepositive tests.…”

“…Iron deficiency anemia is a recognized cause of falsepositive tests. Hemoglobin E heterozygosity also leads to a significant proportion of positive tests [3,5], but this is a strength rather than a weakness of the test since the detection of hemoglobin E is also relevant to antenatal counseling for disorders of globin chain synthesis. Sickle cell trait results in positive tests in 13-40% of instances, depending on the degree of hypotonicity of the saline solution [3,6].…”

Effectiveness of naked eye single tube osmotic fragility test for screening of beta-thalassemia trait from north Maharashtra region, India

“…Earlier studies have recommended the use of 0.32%, 0.34%, 0.36% and 0.40% buffered saline solutions. [6][7][8][9] However, 0.36% solution was comparatively more sensitive but less specific than 0.32% solution. 7 Moreover, when the test is intended to screen α0-thalassemia 0.34% solution was recommended with detection of all β-thalassemia traits also being reported.…”

A Stopped Flow System with Hydrodynamic Injection for Red Blood Cells Osmotic Fragility Test: Possibility for Automatic Screening of Beta-thalassemia Trait

“…The change in osmotic fragility (OF) has been observed when the technique is performed in combination with PCR. 11,12 in various situations where the surface-to-volume ratio or Even though thalassemia patients have some red cells that are membrane physiology of the red cells is altered. [1][2][3] Elevated OF more fragile than normal, a larger portion is less fragile.…”