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294 Comparison of mathematical indices used to differentiate between β-thalassemia and iron deficiency anemia in croatian children
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  1. Daniel Turudic,
  2. Iva Busic,
  3. Marko Bilic,
  4. Ernest Bilic
  1. University Hospital Centre Zagreb

Abstract

The aim of the study is to discriminate β-thalassemia from iron defficiency anemia (IDA) using common mathematical indices.

A complete blood count (CBC) sample of 100 children (aged 6 months – 18 years) treated for β-thalassemia and IDA in Department for Pediatric Hematology and Oncology University Hospital Centre Zagreb was randomly selected. Only children diagnosed with microcytic hypochromic anemia (MCV <80 fl; MCH < 26 pg; hemoglobin < 109 g/l) were enrolled in the study.

Diagnosis of β-thalassemia was confirmed with a hemoglobin A2 level > 3.5% by liquid chromatography while serum iron levels <4 umol/L and serum feritin levels <15 ng/dl indicated iron defficiency anemia (IDA). Children below < 6 months of age or with other diseases that could cause microcytic hypochromic anemia were excluded. Sensitivity, specificity and receiver operating characteristic (ROC) analysis of most common discriminating indices (Matos & Carvalho, Mentzer Index, RDW Index, Green and King, Ehsani Index) used in differential diagnosis of these two diseases was calculated using MedCalc.v15.2 statistical software. Nonparametric nature of the CBC sample was assessed using the Kolmogorov–Smirnov test. Mann–Whitney test was used to investigate differences between the two groups. Area under the ROC curve was calculated for each index and their differences were assessed. A p-value < 0.05 was considered significant.

Among the 5 tested indices, the Ehsani index correctly diagnosed the highest number of children with β-thalassemia, but failed to properly recognize children with IDA (sensitivity 92%, specificity 46%). The most commonly used Mentzer index showed similar results (sensitivity 88%, specificity 48%). The best ratio between sensitivity and specificity was observed for the new Matos & Cavalho index (sensitivity 74%, specificity 88%) with highest area under the ROC curve. Pairwise comparison of ROC curves obseved a significant difference between Matos & Cavalho index and the remaining four tested indices (RDWI p<0,0008; Ehsani p<0,0001; Green and King p<0,0001; Mentzer p<0,0001). Kolmogorov–Smirnov test for normal distribution of CBC values showed a p>0,05 while Mann–Whitney U test for independent samples showed a p<0.05 difference between IDA and β- thalassemia.

Our results show that the most optimal index for discriminating between β- thalassemia and IDA in analysed children is Matos & Cavalho Index.

Therefore, it is more appropriate for discernment than the other analysed indexes. All indexes with low specificity (Mentzer, Ehsani, Green and King) were of low validity as they have a low proportion of IDA correctly identified as such.

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