Clinical to Molecular Screening Paradigm forβ-Thalassemia Carriers

Genetic Study for Identifying Beta Thalassemia Trait in Relatives of Children with Beta Thalassemia Major

BACKGROUND

The most common inherited illness, thalassemia, is thought to have a detrimental effect on public health, particularly in endemic areas. Children with beta thalassemia disease have several mutations. Prevention and premarital examination are still the most effective measures to lessen the burden of beta thalassemia.

OBJECTIVES

This study primarily aimed to determine the beta thalassemia carriers in relatives of beta thalassemia major children, the role of gene study in the confirmation of beta thalassemia trait diagnosis, and to detect the genetic defect in the relatives of beta thalassemia major children.

MATERIALS AND METHODS

The cross-sectional study was conducted on 109 healthy children, aged between six months and 18 years, who were the relatives (second and fourth degree) of beta thalassemia major cases.

RESULTS

Gene screening, using the amplification refractory mutation system (ARMS) polymerase chain reaction (PCR), covered the most common 22 alleles in the Mediterranean region, and was successful in detecting 61.5% of beta-globin chain mutations of studied participants, in addition to high prevalence (34.8%) of beta thalassemia carriers among the relatives of beta thalassemia children.

CONCLUSION

The beta thalassemia carrier rate was found to be highly prevalent among relatives of beta thalassemia major children. Despite the accuracy of gene screening in the detection of beta thalassemia carriers, the use of the most common 22 alleles can only detect 61.5% of carriers; hence, the value of tested gene study is still limited in the detection of carrier rates.

Reliability of hemoglobin A2 value as measured by the Premier Resolution system for screening of β-thalassemia carriers

OBJECTIVES

Accurate quantification of hemoglobin (Hb) A2 is vital for diagnosing β-thalassemia carriers. This study aimed to assess the precision and diagnostic utility of HbA2 measurements using the new high-performance liquid chromatography (HPLC) method, Premier Resolution, in comparison to capillary electrophoresis (CE).

METHODS

We analyzed 418 samples, previously identified as A2A by CE, using Premier Resolution-HPLC. We compared the results, established correlations, and determined an optimal HbA2 cutoff value for β-thalassemia screening. Additionally, we prospectively evaluated the chosen cutoff value in 632 samples. Mutations in the β- and α-globin genes were identified using polymerase chain reaction (PCR) techniques and DNA sequencing.

RESULTS

HbA2 levels were consistently higher with Premier Resolution, yet there was a significant correlation with CE in all samples (bias, -0.33; r, 0.991), β-thalassemia (bias, -0.27; r, 0.927), and non-β-thalassemia carriers (bias, -0.36; r, 0.928). An HbA2 cutoff value of ≥4.0 % for β-thalassemia screening achieved 100 % sensitivity and 99.6 % specificity. Further validation yielded sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 97.3 , 99.8, 97.3, 99.8, and 99.7 %, respectively. We also identified a rare β-Hb variant, Hb La Desirade [HBB:c.389C>T], associated with β-thalassemia and co-inherited with a single α-globin gene.

CONCLUSIONS

The Premier Resolution HPLC is a reliable and accurate method for routine β-thalassemia carrier screening, aligning with existing CE methods.

An efficient isoelectric focusing of microcolumn array chip for screening of adult Beta-Thalassemia

Traditional capillary isoelectric focusing (cIEF), liquid chromatography (LC) and capillary zone electrophoresis (CZE) still suffered from low resolution for hemoglobinopathy screening. Herein, a 30-mm pH 5.2-7.8 microcolumn IEF (mIEF) array chip was developed for hemoglobinopathy screening. As a proof of concept, adult beta-thalassemia was chosen as a model disease. In the method, blood samples were hemolyzed via hemolysin solution and loaded into the microcolumn. The experiments showed that (i) the species of Hb A, F, A₂ and variants were clearly separated in the chip, and the resolution was greatly higher than the ones of LC/CZE/cIEF; (ii) up to 24 samples could be simultaneously analyzed in 12-min run; (iii) the intraday and interday RSDs were respectively 3.32-4.91 % and 4.07-5.33 %. The assays of mIEF to total 634 samples were compared with the ones of LC (n = 327) and PCR (n = 307). The cutoff of 3.5 % HbA₂ led to the sensitivity of 100 % and specificity of 89.1 % for the mIEF-based screening; and there was 96.7 % coincidence between the methods of mIEF and PCR if refer Hb A₂ and F. The method had the merits of facility, efficiency, specificity and sensitivity in contrast to the currently-used methods, implying its potential to screening of beta-thalassemia and hemoglobinopathies.

Problem of borderline hemoglobin A2 levels in an Iranian population with a high prevalence of α- and β-thalassemia carriers

Background

It is difficult to classify a small fraction of α- and β-thalassemia (α- and β-thal) carriers based on their Hb A2 levels. Here, we report the results of a molecular investigation in a cohort of thalassemia carriers with borderline Hb A2 levels originated from western Iran.

Results

The documents of 5956 α- or β-thal carriers were reviewed. The frequency of individuals with borderline Hb A2 levels in this cohort was 436 (7.32%). A total of 12 different α-thal and 27 different β-thal variants were identified in this study.

Conclusions

Our data showed that individuals with borderline Hb A2 are not uncommon in our population. Moreover, preselection of α- and β-thal carriers with borderline Hb A2 levels based on Hb A2, mean corpuscular volume (MCV), and mean cell hemoglobin (MCH) is not advisable in our population. Therefore, it is necessary to investigate both α- and β-globin genes in cases with borderline Hb A2 levels, especially if the partner is a carrier of β-thal or α0-thal.

Prevalence of iron deficiency anemia and beta thalassemia carriers among relatives of beta thalassemia patients in Nile Delta region, Egypt: a multicenter study

BACKGROUND

Screening of β thalassemia among close relatives is more feasible in highly prevalent countries with limited resources. The purpose of this study is to determine the prevalence of β thalassemia carriers and iron deficiency anemia among relatives of β thalassemia patients in Mid Delta, Egypt.

METHODS

This is a cross-sectional multi-center study conducted on 2118 relatives of patients with β thalassemia from different Egyptian governorates in the Mid Delta region. They were subjected to history taking with precise determination of geographic location, general examination, and the following investigations: complete blood counts, serum ferritin for those who showed microcytic hypochromic anemia, and high-performance liquid chromatography for those who were not diagnosed as iron deficiency anemia.

RESULTS

The total prevalence of iron deficiency anemia among close relatives of confirmed β thalassemia patients in the Nile Delta region was 17.19%. The highest prevalence of iron deficiency anemia (45.05%) was reported in Al-Gharbia Governorate, followed by Al-Menoufia Governorate (21.67%), and the lowest prevalence was that of Al-Sharkia Governorate (4.91%). The differences were highly statistically significant (p < 0.001). β thalassemia carrier prevalence rate in the studied relatives was 35.84%, with the highest prevalence detected in Al-Sharkia Governorate (51.32%), followed by Kafr-Alsheikh and Al-Dakahilia Governorates (41.78%, 37.13%) respectively, while Al-Menoufia Governorate had the lowest prevalence rate (25.00%). These differences were also highly statistically significant (p < 0.001).

CONCLUSION

More than one-third of relatives of patients with β thalassemia are carriers of the disease, while 17.19% suffer from iron deficiency anemia. This study demonstrates the importance of tracing the high number of beta thalassemia carriers among relatives of patients with β thalassemia in Egypt.

Strong correlation and high comparability of capillary electrophoresis and three different methods for HbA1c measurement in a population without hemoglobinopathy

The present study aimed to investigate the comparability of capillary electrophoresis (CE) and three different methods for HbA1c measurement. The 270 whole blood samples with normal hemoglobin profiles were analyzed for HbA1c values by the Roche turbidimetric inhibition immunoassay (TINIA), the Mindray enzymatic assay (EA), the Arkray high-performance liquid chromatography (HPLC) in comparison with the Sebia CE. The within-laboratory coefficient of variation of all four methods was within the accepted goal (<2%), showing good performance of all of these methods. Pairwise comparisons of HbA1c values obtained by CE and other methods were determined in both total group and subgroups (HbA1c levels of <6.5%, 6.5-8% and >8%). Mean differences of HbA1c values in all groups were very small in which the mean HbA1c value measured by EA was lower while those by TINIA and HPLC were higher than that of CE. The majority of different values were within the limits of agreement in Bland-Altman analysis, indicating good agreement between CE and the others. Less than 5% of percentage differences were out of the total allowable error limit in all groups, showing that differences of HbA1c values between CE and other methods were not clinically significant. Pairwise comparisons of HbA1c values of CE and the others in Passing-Bablok regression and Spearman rank correlation studies displayed high concordance and strong correlation in all groups. In conclusion, the present study showed strong correlation, high comparability and consistent results for HbA1c measurement between capillary electrophoresis and the other three different methods.