A comparative evaluation of the analytical performances of premier resolution-high-performance liquid chromatography (PR-HPLC) with capillary zone electrophoresis (CZE) assays for the detection of hemoglobin variants and the quantitation of HbA0, A2, E, and F

OBJECTIVES

Hemoglobinopathies, including thalassemia and hemoglobin (Hb) variants, are common hematological disorders in tropical countries. Accurate and precise separation of hemoglobin types and reliable quantitation are necessary for differential diagnosis of these disorders.

METHODS

We have evaluated the analytical performances of premier resolution-high-performance liquid chromatography (PR-HPLC; Trinity Biotech, Co. Wicklow, Ireland) to assist in the presumptive diagnosis of thalassemia and Hb variants commonly found in Southeast Asian countries. HbA0, HbA2, HbE, and HbF levels were separated and quantified in 120 blood samples from unrelated adult subjects and compared with those analyzed by capillary zone electrophoresis (CZE; CAPILLARYS™ 2, Sebia, Norcross, GA, US). The Hb analysis patterns of Hb variants obtained from the PR-HPLC system were also compared to those obtained from HPLC (VARIANT II, β-thalassemia Short Program, Bio-Rad, Laboratories, Hercules, CA, US) and CZE systems.

RESULTS

The PR-HPLC had excellent precision with a coefficient of variation (CV) for HbA2 quantitation of 3.8 % within-run and 5.2 % between-run. The levels of HbA2/E quantified by the PR-HPLC system correlated well with those of the CZE system (r=0.997). In addition, thalassemia interpretation results obtained from the PR-HPLC and the CZE showed 100 % agreement. Moreover, chromatograms of the PR-HPLC were also comparable to those of VII-HPLC and CAP2-CZE electropherograms.

CONCLUSIONS

The PR-HPLC system would be applicable to diagnose common forms of thalassemia and Hb variants in Southeast Asia.

Single-tube multiplex real-time PCR with EvaGreen and high-resolution melting analysis for diagnosis of α0-thalassemia--SEA,--THAI, and--CR type deletions

Regions with a high prevalence of α-thalassemia (α-thal) require simple, rapid, and accurate tests for carrier screening and prenatal diagnosis. Diagnosis of multiple deletions in a single tube is necessary to clearly identify individuals with α0-thalassemia in the routine setting, especially in at-risk couples. Therefore, we aimed to develop a single-tube multiplex real-time PCR with EvaGreen and high-resolution melting (HRM) analysis for the identification of α0-thalassemia Southeast Asian (SEA), Thai and Chiang Rai (CR) type deletions. The results of the HRM analysis indicated that the amplified fragments from α0-thal--CR,--THAI,--SEA, and the wild-type α-globin gene had specific peak heights at mean melting temperature (Tm) values of 85.40°C, 86.50°C, 87.65°C, and 91.04°C, respectively. The frequencies of α0-thal--SEA,--THAI,--CR obtained from routine testing in 2,135 samples were 17.89%, 0.19% and 0.19%, respectively. This method would be useful for preventing Hb Bart's hydrops fetalis. Detection of multiple deletions in a single run is cost-effective, highly accurate and timesaving. This technique could enable wider α-thalassemia diagnosis in high prevalence areas and served as an example for thalassemia routine setting.

Diagnosis of α0-thalassemia Chiang Rai (--CR) deletion by melt curve analysis in Northern Thailand

A large novel 44.6 kb deletion named α⁰-thalassemia Chiang Rai (--^CR) was first described in the individuals with uncommon Hb Bart's hydrops fetalis and HbH disease. This study aimed to develop a real-time gap PCR and melt curve analysis for the detection of --^CR and investigate its frequency in northern Thailand. Among 4,952 blood samples, the assay was performed in 525 samples with a mean corpuscular volume (MCV) < 80 fL, HbA₂ < 3.5%, HbA₂+E < 25%, and negative for common deletional α⁰-thalassemia --^SEA and --^THAI. The developed method showed T_m values of 85.8 ± 0.0 °C and 91.5 ± 0.1 °C, which were specific for --^CR and wild-type alleles, respectively. Nine (0.18% of 4,952 or 1.71% of 525) were positive for --^CR, in which two were HbH disease and the rest were heterozygous for --^CR. This study demonstrated the success of real-time gap PCR with melt curve analysis for --^CR diagnosis. Additionally, the prevalence of --^CR in the northern Thai population was comparable to --^THAI. Thus, this study implies the importance of --^CR in northern Thailand. Moreover, the developed real-time gap PCR with melt curve analysis is simple and highly accurate, and may be considered as an additional tool for routine α⁰-thalassemia --^CR diagnosis in this region.

Multiplex Quantitative Real-Time Polymerase Chain Reaction and High-Resolution Melting Analysis for Identification of a Couple At-Risk of Having a Newborn with Severe Thalassemia

Many polymerase chain reaction (PCR)-based techniques have been used for routine diagnosis of α- and β-thalassemias. However, most require a multi step of post-PCR processes that are time-consuming and labor-intensive procedures. This study reported the successful use of multiplex quantitative real-time PCR (qPCR), with high-resolution melting (HRM) analysis for diagnosis of two common deletional α⁰-thalassemia (α⁰-thal) and 15 common β-thalassemia (β-thal) mutations, in order to identify a couple at-risk of having a newborn with severe thalassemia in the northern region of Thailand. With this approach, 22 (7.2%) of 306 couples were diagnosed as being at-risk for having a child with severe thalassemia, including three homozygous α⁰-thal, five homozygous β-thal and 14 Hb E (HBB: c.79G>A)/β⁰-thal disease. Our findings indicated that multiplex qPCR with HRM is applicable for routine molecular diagnosis in order to identify a couple at-risk of having a newborn with severe thalassemia, especially in an endemic region.

Hb Bart's Hydrops Fetalis Syndrome and Hb H Disease Caused by Deletional Chiang Rai (- -CR) α0-Thalassemia in Two Unrelated Thai Families

α⁰-Thalassemia (α⁰-thal) Chiang Rai (- -^CR; NC_000016.10: g.144215_188843del) was identified as a novel 44.6 kb deletional type of α-thalassemia (α-thal), removing all α-like globin genes. However, little is known about the deleterious effects of this genetic disorder, particularly when it is combined with other types of thalassemia. We performed molecular analysis of the - -^CR deletion using gap-polymerase chain reaction (gap-PCR) in two independent families residing in Phayao and Chiang Mai, Thailand, with an unknown causative mutation for Hb Bart's hydrops fetalis syndrome and Hb H disease. Five out of seven individuals were diagnosed to be heterozygous for the - -^CR deletion. Of these, two also carried Hb H disease with compound heterozygosities for - -^CR and -α^3.7 (rightward) deletions. However, hematological parameters of the - -^CR carriers displayed microcytic hypochromic anemia that is comparable to other α⁰-thal traits. Although the prevalence of - -^CR has never been elucidated in a specific population, our study demonstrated that genotyping for - -^CR might be considered as an additional investigation for unexplained Hb Bart's hydrops fetal syndrome and Hb H disease.

Validation of Microarray for the Simultaneous Detection of Common α- and β-Thalassemia Gene Mutations

BACKGROUND

Methods for detecting the complex genetic characteristics of α- and β-thalassemias are required for preventing and controlling the outbreak of new cases.

METHODS

We evaluated the accuracy and practical utility of microarray for simultaneous detection of α- and β-thalassemias. A total of 102 DNA specimens, which represented 25 different genotypes, were tested in parallel using the microarray and reference methods used in the thalassemia laboratory of the Associated Medical Sciences-Clinical Services Center (AMS-CSC), Chiang Mai, Thailand.

RESULTS

A total of 100 (98.0%) DNA specimens were completely concordant between the microarray and reference methods, whereas discrepancies between the different methods were observed in only 2 DNA specimens with homozygous hemoglobin E (HbE).

CONCLUSIONS

The microarray appeared to be a fast, easy to perform, and accurate method for simultaneous detection of α- and β-thalassemias in Thailand and Southeast Asian countries. However, this technique needs to be improved and validated in a larger number of specimens with homozygous HbE before further routine laboratory use.