The role of discriminant functions in screening beta thalassemia trait and iron deficiency anemia among laboratory samples

Abstract

INTRODUCTION:Most important differential diagnosis for microcytosis and hypochromia is beta thalassemia trait (BTT) and iron deficiency anemia.AIM:To study the utility of discriminant functions (DFs) and red cell indices in distinguishing BTT and iron deficiency anemia.METHODS:The study is observational (cross sectional). A total of 350 patients, 43 BTT, and 307 iron-deficiency anemia reflecting actual disease prevalence were included. Their complete red blood cell parameters, hemoglobin A2, and serum ferritin level wherever required were obtained. Receiver operator characteristic curve was drawn for each DF and results compared with other studies.RESULTS:Among the six DFs, the highest sensitivity (97.7%) and specificity (98.6%) was shown, respectively, by Shine and Lal (S and L) and England and Fraser index (E and F) in identifying cases of BTT. Youden index of the Mentzer index (MI) was the highest (69.0) and S and L, the lowest (13.2) indicating MI to be the most efficient and the S and L, the least in differentiating the two entities. Red cell distribution width index (RDWI) showed the highest accuracy (91.6%), whereas S and L showed the least accuracy (29.6%).CONCLUSION:MI was the most efficient in discriminating BTT from iron deficiency anemia (IDA). RDWI stands to be the most accurate. S and L could at best be used as screening tool rather than DF. No study except one agreed with us because convenient sampling used in other studies generated bias in their results. Statistically, this study bears far more relevance than other studies because the sample distribution reflects the prevalence of IDA and BTT in the community.

Beta Thalassemia Trait

“…Many formulae have been proposed for probable diagnosis of beta thalassemia trait. 2,7 But in the present study, the only formula which gives above 90% sensitivity is shine and lal index. According to srivastava index, the value of less than 3.8 is indicative of beta thalassemia trait.…”

“…2 The laboratory tests required for the diagnoisis of beta thalassemia include hemoglobin concentration, red blood cell count and mean corpuscular volume, with addition of examination of peripheral blood smear. 2,6,7 Usually, the complete blood counts show low hemoglobin, decreased MCV of less than 75 fL, low MCH of less than 25 pg and raised RBC count > 5.0 millions/cmm. 2 The final definitive diagnosis of beta thalassemia trait is made by Haemoglobin electrophoresis.…”

“…2 Microcytic hypochromic blood picture is seen in beta thalassemia trait as well as iron deficiency anemia. 6,7,8 Serum ferritin, iron and HbA2 level are required to differentiate beta thalassemia trait from iron deficiency anemia. 6,9 Beta thalassemia should be differentiated from iron deficiency anemia because hemoglobin level does not improve in the earlier and iron supplements in such cases may lead to iron overload.…”

Beta Thalassemia Trait;

“…26 In one study, highest sensitivity of 79.1% was found for srivastava index. 7 Ehsani et al and Batebi et al observed Mentzers Index as the best discriminatory index. 27,28 These findings are not consistent with our study.…”

Thalassemia carrier detection among pregnant women

“…and have been proposed to better distinguish between β-thalassemia carrier and iron deficiency anemia (IDA). 5 Therefore, the aim of this study was to assess the possibility of thalassemia carrier screening in the eastern part of Indonesia, where laboratory facility is limited by using erythrocyte indices. We explored the type of thalassemia mutation since the population in eastern Indonesia has a different genetic background than the population in the west.…”