Efficacy of Hematological Indices for β Thalassemia Trait Screening in Pregnant Women

Abstract

Background: ß thalassemia is one of commonest inherited disorder in Pakistan having a carrier rate of 5%. Pregnant women having ß thalassemia trait can have offspring having ß thalassemia major which is lifelong blood transfusion dependent state. Different screening programmes are being carried out in various parts of the world so that the birth of children having ß thalassemia major can be effectively reduced.Objective: To determine the diagnostic accuracy of hematological parameters in identifying β thalassemia trait in pregnant women keeping measurement of HgbA2 as gold standard.Methods: 108 pregnant women were enrolled during one year of the study period. Blood sample was taken and blood complete picture was obtained. By using variables of CP card Green & King index, Shine & Lal index and RDWI were calculated keeping hemoglobin electrophoresis as gold standard. Results:The age of patients ranged from 17 to 37 years with mean age of 24.65. Out of 108 pregnant women enrolled in study 40 were found to have ß thalassemia trait based on results of hemoglobin electrophoresis. Shine & Lal index showed 100% sensitivity, 0% specificity, 35% PPV and 0% NPV. Green & Kings index had sensitivity of 32%, specificity 100%, PPV of 100% and NPV of 71% while RDWI showed 50% sensitivity, 100% specificity, PPV of 100% and NPV of 77% in diagnosing ß thalassemia trait in pregnant women. Conclusion:Automated cell counters based formula including Green & King index, Shine &Lal index and RDWI provide rapid, reliable and cost effective method for screening of ß thalassemia trait especially in third world countries like Pakistan. However none of them have 100% sensitivity and specificity. So they should be collectively looked at in screening programmes.