Effectiveness of red cell osmotic fragility test with varying degrees of saline concentration in detecting beta-thalassaemia trait.

INTRODUCTION: This study was performed with the objective of determining the efficacy of naked eye single tube red cell osmotic fragility test (NESTROFT) as a screening test for beta-thalassaemia trait, and to standardise a saline concentration which could give best results with minimum error and maximum sensitivity and specificity.
METHODS: Five concentrations (0.35 percent, 0.36 percent, 0.37 percent, 0.38 percent and 0.39 percent) of buffered saline solutions were used. NESTROFT was applied to three groups of subjects: 24 normal individuals, 87 subjects with genetically-proven beta-thalassaemia trait and 13 patients with proven iron-deficiency anaemia.
RESULTS: The results demonstrated that 0.36 percent was the best saline concentration for NESTROFT. It could detect 97.7 percent of heterozygous beta-thalassaemia patients, compared to 94.25 percent, 91.95 percent, 88.51 percent and 82.76 percent detection rates obtained with 0.35 percent, 0.37 percent, 0.38 percent and 0.39 percent saline concentrations, respectively. Specificity of NESTROFT with 0.36 percent saline was also higher at 83.3 percent, whereas that of 0.35 percent, 0.37 percent, 0.38 percent and 0.39 percent was 79.17 percent, 79.17 percent, 70.83 percent and 62.5 percent, respectively. This test with 0.36 percent saline concentration was also positive for three (23.08 percent) patients with iron-deficiency anaemia.
CONCLUSION: NESTROFT done with 0.36 percent buffered saline solution provides more accurate results compared to the other concentrations tested. Since the test is sensitive, cost-effective, rapid and reliable, it may be considered as the single screening test to be used in areas with limited laboratory facilities and economic resources.