Evaluation of body iron status in Italian carriers of beta-thalassemia trait

A new index to discriminate between iron deficiency anemia and thalassemia trait

Background

The most common microcytic and hypochromic anemias are iron deficiency anemia and thalassemia trait. Several indices to discriminate iron deficiency anemia from thalassemia trait have been proposed as simple diagnostic tools. However, some of the best discriminative indices use parameters in the formulas that are only measured in modern counters and are not always available in small laboratories.

The development of an index with good diagnostic accuracy based only on parameters derived from the blood cell count obtained using simple counters would be useful in the clinical routine. Thus, the aim of this study was to develop and validate a discriminative index to differentiate iron deficiency anemia from thalassemia trait.

Methods

To develop and to validate the new formula, blood count data from 106 (thalassemia trait: 23 and iron deficiency: 83) and 185 patients (thalassemia trait: 30 and iron deficiency: 155) were used, respectively. Iron deficiency, β-thalassemia trait and α-thalassemia trait were confirmed by gold standard tests (low serum ferritin for iron deficiency anemia, HbA₂ > 3.5% for β-thalassemia trait and using molecular biology for the α-thalassemia trait).

Results

The sensitivity, specificity, efficiency, Youden's Index, area under receiver operating characteristic curve and Kappa coefficient of the new formula, called the Matos & Carvalho Index were 99.3%, 76.7%, 95.7%, 76.0, 0.95 and 0.83, respectively.

Conclusion

The performance of this index was excellent with the advantage of being solely dependent on the mean corpuscular hemoglobin concentration and red blood cell count obtained from simple automatic counters and thus may be of great value in underdeveloped and developing countries.

Red cell indices: differentiation between β-thalassemia trait and iron deficiency anemia and application to sickle cell disease and sickle cell thalassemia

BACKGROUND

In Tunisia, thalassemia and sickle cell disease (SS) represent the most prevalent monogenic hemoglobin disorders with 2.21% and 1.89% of carriers, respectively. This study aims to evaluate the diagnosis reliability of 12 red blood cell (RBC) indices in differentiation of β-thalassemia trait (β-TT) from iron deficiency anemia (IDA) and between homozygous SS and sickle cell thalassemia (ST).

METHODS

The study covered 384 patients divided into three groups. The first one is composed of 145 control group, the second consists of 57 β-TT and 52 IDA subjects and the last one with 88 SS and 42 ST patients. We calculated sensitivity, specificity, positive-predictive values, negative-predictive values, percentage of correctly identified patients and Youden's Index (YI) for each indice. We also established new cut-off values by receiver operating characteristic curves for each indice. An evaluation study was performed on another population composed of 106 β-TT, 125 IDA, 31 SS, and 17 ST patients.

RESULTS

Srivastava Index (SI) shows the highest reliability in discriminating β-TT from IDA at 5.17 as a cut-off and also SS from ST with 7.7 as another threshold. Mentzer Index (MI) and RBC appear also useful in both groups with new cut-offs slightly different from those described in literature for β-TT and IDA.

CONCLUSIONS

The effectiveness and the simplicity of calculation of these indices make them acceptable and easy to use. They can be relied on for differential diagnosis and even for diagnosis of β-TT with atypical HbA₂ levels.

Comparison of discriminative indices for iron deficiency anemia and β thalassemia trait in a Brazilian population

To discriminate iron deficiency anemia (IDA) from β thalassemia trait (βTT), several indices obtained from modern blood count analyzers have been reported. Discrimination power of seven indices to differentiate between IDA and βTT, such as Green and King Index (GKI), RDW Index (RDWI), Srivastava Index (SRI), Mentzer Index (MI), Shine and Lal Index (SLI), Ehsani Index (EI), and Sirdah Index (SI), were evaluated. These indices were applied on 47 patients with βTT and on 289 patients with IDA, as confirmed by gold standard tests. Sensitivity, specificity, positive and negative predictive values, efficiency, area under receiver-operating characteristics curve (AUC), and Youden's Index (YI) were calculated. GKI and RDWI showed the highest reliability, as they had the largest AUCs (0.919, 0.912, respectively) and Youden's Index (70.4, 74.6, respectively). Conversely, SLI presented a less satisfactory performance (AUC = 0.786 and YI = 6.6). Data taken together suggest the superiority of GKI and RDWI to discriminate between IDA and βTT.