Iron deficiency does not compromise the diagnosis of high HbA(2) β thalassemia trait.

Hemoglobinopathies are the only genetic disease in which it is possible to detect carriers using hematologic findings rather than DNA analysis. Complete screening is based on the detection of red cell indices, HbA2, HbF and hemoglobin variant values. The classical phenotype of heterozygous b-thalassemia includes an elevated HbA2 level (3.4-6.0%), a relatively high red cell count, a markedly reduced mean corpuscular volume (MCV 60-75 fL) and reduced mean corpuscular hemoglobin levels (MCH 18-24 pg).HbA2 determination plays a key role in screening programs for b-thalassemia because a small increase in this fraction is the most important marker of b-thalassemia heterozygous carriers.Measurement of HbA2 is undertaken in many laboratories worldwide, often with a lack of agreement in the obtained result. This is probably because there is no international standardization of HbA2 determination. Reduced production of b-globin, with a relative excess of α-globin chains, and also a “compensatory” increase in d-globin synthesis, favor the formation of αd dimmers and the assembly of HbA2 tetramers. Low HbA2 values are in most instances the result of either reduced synthesis of the d-globin chain, or posttranslational modifications in the assembly of the HbA2 tetramer due to a reduction in the synthesis of α-globin chains. Some authors have reported that iron deficiency (ID) is a potential source of diagnostic interference in tests for HbA2 determination that may give false-positive or negative results. In fact, intracellurar lack of iron reduces a-globin chain synthesis relative to that of non-α globin chains; when the supply of b-globin chains is limited, b-globin chains compete more effectively for α-globin chains than d-globin chains, resulting in reduced levels of Hb A2. Studies from India reported that the b-thalassemic trait does not confer an advantage in maintaining iron balance, and that HbA2 is not significantly lowered in the presence of ID. In Sicily, there is a high heterogeneity of molecular defects and a prevalence of mutations causing bor bthalassemia, so that a reliable HbA2 assessment is essential for accurate diagnosis and genetic counseling. The purpose of the present study was to quantify the effect of iron deficiency on HbA2 levels in order to improve the detection of b thalassemia trait with and without iron deficiency. This study was approved by the Ethical Committee of the Villa Sofia-Cervello Hospital, Palermo, and informed consent was obtained from all subjects. A retrospective analysis was carried out on 9,625 samples, without Hb variants, obtained during a program for b-thalassemia carrier screening in the Sicilian population in the last two years. We selected 1,133 samples with estimated serum ferritin and 253 samples with estimated serum ferritin and molecular analysis result. Blood samples from all patients were collected and analyzed as previously described. For statistical analysis, we divided these samples into two groups, A and B, using serum ferritin value of 30 mg/L as cut off. Figure 1 shows the profile of study performed in this work. Given that ferritin is an acute-phase protein, samples with altered white blood cell indices were excluded from analysis to avoid a potential bias. All statistical analyses were performed with STATA 9 (StataCorp, Texas, USA). Means are reported with standard deviation (SD); proportions and differences are reported with 95% confidence intervals (CI). A Receiver Operating Characteristic (ROC) analysis was performed to determine sensitivity and specificity of the test in group A