Background and Objectives
Iron deficiency anemia (IDA) and ß thalassemia trait (TT) are the most common forms of microcytic anemia. Some discrimination indices calculated from red blood cell count and red blood cell indices are defined and used for rapid discrimination between TT and IDA. Youden's index is the most reliable method to measure the validity of a particular technique, because it takes into account both sensitivity and specificity.
Materials and Methods
We calculated 10 discrimination indices (Mentzer Index, England and Fraser Index, Srivastava Index, Green and King Index, Shine and Lal Index, red blood cell (RBC) count, red blood cell distribution width, red blood cell distribution width index (RDWI), Mean Density of Hemoglobin per Liter of blood (MDHL) and Mean Cell Hemoglobin Density (MCHD)) in 170 patients with IDA and in 153 patients with b TT (βTT). We divided the patients into two different age ranges of 1 to 10 and 10 to 57 years.
We determined the number of correctly identified patients by using each discrimination index. None of the indices showed sensitivity and specificity of 100% in the latter group it was just Shine and Lal Index (S and L) that showed a sensitivity close to 90% and specificity of 100% in the former group. The accuracy order of these discrimination indicies from higher to lower for the former was Shine and lal > RBC Count > Srivastava > Mentzer > England and Fraser > Green and King > RDWI > RDW and in the latter RDWI > RBC count > Mentzer > England and Fraser > Srivastava > RDW > Shine and Lal > Green and King. Youden's index for Shine and lal and RBC Count, and for RDWI and RBC Count has the highest diagnostic value in the former and latter groups respectively. Mean Cell Hemoglobin Density (MCHD) and Mean Density of Hemoglobin per Liter (MDHL) did not show any diagnostic value.
None of the indices was completely sensitive and specific in differentiating between b TT and IDA. MCHD mean and median were very close to normal values for both IDA and b TT patients, but in case of MHDL we have found mean and median values being significantly higher than normal values in b TT and lower in IDA patients. In our study, Youden's index of RBC count and RDWI were the highest ones and they were the most reliable discrimination indices in differentiating b TT from IDA in the latter group while for patients in the former RBC and S & L were the most reliable discrimination indices.
Key words : b thalassemia, Iron deficiency anemia, Indices