Objective: To determine the sensitivity and specificity of single-tube osmotic fragility (SOFT) and its
different methods as screening test for thalassemia trait.
Methods: A cross-sectional study was
conducted at Omair Sana Foundation. A total of 400 participants were included in the study. Three
hundred were known thalassemia carriers (parents with at least one child with thalassemia major), while
100 were healthy blood donors. SOFT was performed on all 400 participants. Serum iron, ferritin, and
DNA tests were performed on 100 participants (donors). ARMS technique was used for detecting
thalassemia mutations. Results: Sensitivity and specificity of SOFT (venous method) were found to be
99.6% and 86%, respectively, while with EDTA method, sensitivity was 95% and specificity was 96%.
For venous and EDTA methods, positive predictive values were 95.5% and 98.6%, respectively, while
negative predictive values were 98.8% and 86.6%, respectively. Use of EDTA and storage had an effect
on the results. Sensitivity of SOFT was 95% at 5 min, while it decreased to 87% with EDTA method at
240 min. Sensitivity of SOFT for iron deficiency anemia was found to be 14%.
Conclusion: SOFT can be
used as screening test for thalassemia trait in a cost-effective way. Moreover, we also found that SOFT
should be performed on venous blood without adding preservatives (EDTA) that can interfere with the
results