SYTO9 and SYBR GREEN1 with high resolution melting analysis for molecular confirmatory testing of the common Southeast Asian beta(0)-thalassemia mutations

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.

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.

A novel gap-PCR with high resolution melting analysis for the detection of α-thalassaemia Southeast Asian and Filipino β°-thalassaemia deletion

Homozygosity for the α-thalassaemia Southeast Asian (α-SEA) and Filipino β⁰-thalassaemia (β-FIL) deletions can cause serious complications leading to foetal death or life-long blood transfusions. A rapid and accurate molecular detection assay is essential in populations where the deletions are common. In this study, gap-polymerase chain reaction (PCR) with high resolution melting (HRM) analysis was developed to detect both the large deletions. Melting curves at 86.9 ± 0.1 °C were generated by normal individuals without the α-SEA deletion, 84.7 ± 0.1 °C by homozygous α-SEA deletion individuals and two melting curves at 84.7 ± 0.1 °C and 86.9 ± 0.1 °C by α-SEA deletion carriers. Normal individuals without the β-FIL deletion produce amplicons with a melting temperature (Tm) at 74.6 ± 0.1 °C, homozygous β-FIL individuals produce amplicons with Tm at 73.6 ± 0.1 °C and heterozygous β-FIL individuals generate two amplicons with Tm at 73.6 ± 0.1 °C and 74.6 ± 0.1 °C. Evaluation using blinded tests on 220 DNA samples showed 100% sensitivity and specificity. The developed assays are sensitive and specific for rapid molecular and prenatal diagnosis for the α-SEA and β-FIL deletions.

Red Cell Indices and Formulas Used in Differentiation of β-Thalassemia Trait from Iron Deficiency in Thai Adults

β-Thalassemia (β-thal) and iron deficiency cause most microcytic anemias. Red cell indices and formulas have been established as simple, fast, and inexpensive in discrimination between these two hematological disorders in school children. However, whether these formulas could be applied to diagnose β-thal trait and iron deficiency in adult Thai subjects is unclear. The aim of this study was to examine the diagnostic accuracy of five red cell indices [red blood cell (RBC) counts, mean corpuscular volume (MCV), mean corpuscular hemoglobin (Hb) (MCH), mean corpuscular Hb concentration (MCHC), and red cell distribution width (RDW)] and nine formulas (RDW/RBC, RDW Index, Sirdah, Green and King, Mentzer, England and Fraser, Ehsani, Srivastava and Shine and Lal). Their sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV), efficiency, and Youden's Index were analyzed in 102 β-thal trait and 64 iron deficiency adult Thai subjects. The RDW/RBC formula proved to be the most reliable index as they had 100.0% specificity and PPV and the highest efficiency (94.58%) and Youden's Index (91.18%), as well as high sensitivity (91.18%) and NPV (87.67%). Therefore, this formula could be used in initial discrimination of β-thal trait from iron deficiency in adult Thai subjects.

Red cell indices and formulas used in differentiation of β-thalassemia trait from iron deficiency in Thai school children

Red cell indices and formulas have been established as simple, fast, and inexpensive means for discrimination between the β-thalassemia (β-thal) trait and iron deficiency. However, there were no reports of the diagnostic reliability of different red cell indices and formulas in discrimination of β-thal trait from iron deficiency in the Thai population. The aim of this study was to examine the diagnostic accuracy of five red cell indices [red blood cell (RBC) count, mean corpuscular volume (MCV), mean corpuscular hemoglobin (Hb) (MCH), mean corpuscular Hb concentration (MCHC), and red cell distribution width (RDW)] and eight formulas (Sirdah, Green & King, RDW Index, Menzler, England & Fraser, Ehsani, Srivastava, and Shine & Lal). Their sensitivity, specificity, positive and negative prognostic value and efficiency, were analyzed in 77 Thai school children, 21 with the β-thal trait and 56 with iron deficiency. The Sirdah and Srivastava formulas proved to be the most reliable indexes as they had 100.0% sensitivity and negative predictive value, the highest efficiency (97.4%), and the highest Youden's Index value (96.4%). Therefore, these formulas could be used in initial discrimination of the β-thal trait from iron deficiency in Thai school children.

Coinheritance of Hb S [β6(A3)Glu→Val, GAG>GTG] with β0-thalassemia codon 17 (A>T) in a Thai patient

Hb S [β6(A3)Glu→Val, GAG>GTG] is a β-globin gene variant that has a very low incidence in the Thai population. Coinheritance of Hb S and β(0)-thalassemia (β-thal) can result in severe clinical conditions. This study reports the case of a Thai patient with a compound heterozygosity for Hb S and β(0)-thal codon 17 (A>T). His hemoglobin (Hb), hematocrit (packed cell volume, PCV), mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) levels were all less than the lower limits, while red cell distribution width (RDW) was higher than the upper limit. Levels of Hbs S, F and A(2) detected by high performance liquid chromatography (HPLC) were comparable to those from capillary electrophoresis (CE). As Hb S has a similar electrophoretic mobility and the HPLC profile is also similar to those of Hb Tak [β147, Term→Thr (+AC)] and Hb D-Punjab [β121(GH4)Glu→Gln, GAA>CAA], DNA sequencing was then performed. This was to detect β(0)-thal, and to differentiate Hb S from the Hb Tak and Hb D-Punjab mutations. The β(0)-thal codon 17 and Hb S mutations were detected indicating that coinheritance of these two mutations can be found in the Thai population. Therefore, to provide proper clinical management and genetic counseling of this rare case, DNA analysis should be performed in all cases when a peak at the S-window is detected by HPLC or CE.

Interference of hemoglobin Hope on beta-thalassemia diagnosis by the capillary electrophoresis Method

The β-chain hemoglobin (Hb) variants interfere with the diagnosis of β-thalassemia trait using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). We analyzed the effect of Hb Hope, a β-chain Hb variant frequently found in the Thai population, on β-thalassemia trait diagnosis. HPLC and CE were used to quantify the level of HbA(2) in 11 whole blood samples containing Hb Hope. The levels of Hb Hope detected by both methods were similar. An elevated HbA(2) level was found in all samples analyzed by the CE method, while 1 was increased when analyzed by HPLC, which was a compound heterozygous of Hb Hope and α-thalassemia-1 SEA-type deletion. Of 11 samples, 6 had mean corpuscular volumes within the reference range. All samples showed negative results for molecular analysis of β(0)-thalassemia codon 17, 41/42, and 71/72 mutations and β-thalassemia 3.5-kb deletion. Therefore, Hb Hope interfered with the diagnosis of β-thalassemia trait analyzed by CE but not by HPLC.

Detection of α-thalassemia-1 Southeast Asian and Thai type deletions and β-thalassemia 3.5-kb deletion by single-tube multiplex real-time PCR with SYBR Green1 and high-resolution melting analysis

Background

Prevention and control of thalassemia requires simple, rapid, and accurate screening tests for carrier couples who are at risk of conceiving fetuses with severe thalassemia.

Methods

Single-tube multiplex real-time PCR with SYBR Green1 and high-resolution melting (HRM) analysis were used for the identification of α-thalassemia-1 Southeast Asian (SEA) and Thai type deletions and β-thalassemia 3.5-kb gene deletion. The results were compared with those obtained using conventional gap-PCR. DNA samples were derived from 28 normal individuals, 11 individuals with α-thalassemia-1 SEA type deletion, 2 with α-thalassemia-1 Thai type deletion, and 2 with heterozygous β-thalassemia 3.5-kb gene deletion.

Results

HRM analysis indicated that the amplified fragments from α-thalassemia-1 SEA type deletion, α-thalassemia-1 Thai type deletion, β-thalassemia 3.5-kb gene deletion, and the wild-type β-globin gene had specific peak heights at mean melting temperature (T_m) values of 86.89℃, 85.66℃, 77.24℃, and 74.92℃, respectively. The results obtained using single-tube multiplex real-time PCR with SYBR Green1 and HRM analysis showed 100% consistency with those obtained using conventional gap-PCR.

Conclusions

Single-tube multiplex real-time PCR with SYBR Green1 and HRM analysis is a potential alternative for routine clinical screening of the common types of α- and β-thalassemia large gene deletions, since it is simple, cost-effective, and highly accurate.

SYTO9 and SYBR GREEN1 with a high-resolution melting analysis for prenatal diagnosis of β⁰-thalassemia/hemoglobin-E

The β⁰-thalassemia/Hb-E causes a wide range of severe conditions. A high medical cost is incurred in severe cases. Thus, the prevention of new cases of β⁰-thalassemia/Hb-E is required. The aim of this study is to use the SYTO9 and SYBR GREEN1 high-resolution melting (HRM) analysis for prenatal diagnosis of β⁰-thalassemia/Hb-E. DNA samples were extracted from amniotic fluid or cord blood of 11 pregnancies whose fetuses were at risk for β-thalassemia/Hb-E. PCR products from multiplex amplification refractory mutation system PCR for the detection of β⁰-thalassemia mutations at codons 17(A>T), 41/42(-TCTT), and 71/72(+A) and from amplification refractory mutation system PCR for the detection of Hb-E were characterized by SYTO9 HRM analysis. Moreover, β⁰-thalassemia 3.5- kb deletion was detected using real-time PCR with SYBR GREEN1 HRM analysis. Seven of 11 fetuses (64%) were diagnosed as β⁰-thalassemia/Hb-E (4 fetuses with mutation at codon 17, 2 with mutation at codon 41/42, and 1 with 3.5- kb deletion). Results from HRM analysis were completely consistent with those from fetal blood samplings analyzed at the time of delivery or pregnancy termination using HPLC. Therefore, the HRM analysis is easy to use. It is simple, flexible, non-destructive and has superb sensitivity and specificity. This approach might facilitate the laboratory diagnosis and genetic counseling for regions with a high prevalence of β⁰-thalassemia/Hb-E.