The term Thalassemia is derived from Greek word thalassa that means 'the sea' (Mediterranean) mia' means blood. It is also called Mediterranean anemia or Cooley's disease because it is endemic in regions of Mediterranean, Africa, Southeast Asia, Southern China, India and Pakistan 1. Population migration and intermarriage between different ethnic groups has introduced thalassemia in almost every country of the world, including Northern Europe where thalassemia was previously absent. It has been estimated that about 1.5% of the global population (80 to 90 million people) are carriers of betathalassemia, with about 60,000 symptomatic individuals born annually, the great majority in the developing world. (Galanello and Origa Orphanet Journal of Rare Diseases 2010, 5:11)Thalassemia is autosomal recessive disease results in quantitative defects of globin chains results in anemia. It is most common hemoglobinopathy worldwide with carrier rate of 1.7% and high prevalence in Asia including Pakistan comprising of nine million carriers results in more than 5000 transfusion dependent children per year 2, 3, 4. In Pakistan, for instance, patients who receive regular transfusions do not receive iron chelation. Moreover, bone marrow transplantation is not usually available in developing countries. In these regions of the world, prevention is the least expensive and most effective means of dealing with the b-thalassemias. (N Engl J Med, Vol. 347, No. 15 Â· October 10, 2002 Â· www.nejm.org)
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A case control study of 503 subjects was carried out on patients undergoing investigations in the Dow Diagnostic, Research & Reference Lab (DDRRL) Karachi, from the period January 2010 to June 2010. The samples were collected from 253 cases with MCV <80 fl Inclusion criteria were MCV <80 fl and/or MCH < 27 pg on automated haematology analyser. The clinicopathological information on each case including age, gender, and marital status, history of blood disorders, consanguinity, and history of iron therapy was obtained from the case record and direct interviews. Prior to enrolment, the cases were informed about the purpose of the study and the necessity for obtaining related information. The subjects, who willing to participate were requested to fill in a questionnaire. Persons with MCV >80 and with Hb within normal ranges were taken as control through same procedure. Pregnant women, persons with history of chronic inflammatory disorders and history of blood transfusion within 3 months were excluded from study.
Twenty Î¼l of whole blood collected in EDTA pipetted into a glass test tube (100 x 10 mm) containing 4 ml of 0.36% buffered saline solution. Shaken the tube and left at room temperature for 20 minutes. Shaken again the tube and read the three sharp black lines behind the tube. The results were recorded as negative if lines were clearly visible, positive when lines were not visible and doubtful when lines were partially visible. The doubtful cases were considered positive for BTT.
NESTROFT was performed on all 253 cases. The results of 125 cases were confirmed on Hb electrophoresis for BTT. Out of 125 cases 65 were estimated with BTT and 52 had normal HbA2 levels. In 65 cases of BTT, NESTROFT was true positive in 60 cases (92.3%) and false negative in 5 cases (7.6%). Total 52 cases were not estimated with BTT on HbE, NESTROFT was true negative in 45 cases (86.5%) and false positive in 7 cases (13%). On Hb electrophoresis 8 cases were estimated with other hemoglobinopathies. NESTROFT was true positive in all 8 cases (100%). The results are summarized in flow chart. (Figure 4.3)
The sensitivity of NESTROFT to detect BTT in microcytic hypochromic was 92.3%, specificity was 86.53%, positive predictive value was 89.5% and negative predictive value was 90%. Efficiency of test was calculated as 89.74%. Summary of results are shown in flow chart (Figure 4.3.)
Mohamed M et al in1999 conducted study on 382 patients of which 34 patients were diagnosed as BTT based on Hb electrophoresis. HbA2 values more than 3.5% on elution were diagnosed as BTT.(94) Desai S. N. et al in 1998 included 95 cases for comparison of CAE electrophoresis with Fast protein liquid chromatography (FPLC).They found both techniques were equally comparable and reproducible.(79) Khin Ei Han in 1992 studied 133 cases of BTT. Mean HbA2 was 5.7 Â± 1.3 which was significantly higher than normal controls.(64) In the present study the mean HbA2 was 3.97 Â± 0.14 (P 0.001). The mean HbA2 was found to be slightly lower. In population where IDA is prevalent HbA2 levels are found to be significantly lower.(100) Coinheritance of delta Î² thalassemia also lowers HbA2 levels.(101) In the present study the mean HbA2 was found to be slightly lower which may be due to co- existence of IDA.
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Hence we conclude that the differentiation of BTT from Non BTT has important clinical implication in hematology and medicine. The present study demonstrates that set of cost effective screening tests like NESTROFT, DF3 and DF5 along with routine hemogram data (RBC indices) in microcytic cases can effectively discriminate between BTT and Non BTT.
We recommend that NESTROFT with DF3 and DF5 can be use as screening tool for BTT.