Quantitation of hemoglobin components by high-performance cation-exchange liquid chromatography: its use in diagnosis and in the assessment of cellular distribution of hemoglobin variants

The radiation response measurement of a single and multiple cell ionization of neuroblastoma cells by infrared laser trap

Neuroblastoma (NB) is a common type of cancer found mostly in infants and arising from the immature neural crest cells of the sympathetic nervous system. Using laser trapping (LT) technique, the present work contributes to advancing radiotherapy (RT), a leading treatment method for cancer. A single, 2-cells, 3-cells, 4-cells, and 5-cells were trapped using the high-intensity gradient infrared laser at 1064 nm and allowed to become ionized. In this work, a systematic study of Threshold Ionization Energy (TIE) and Threshold Radiation Dose (TRD) versus mass for both single and multi-cell ionization using laser trapping (LT) techniques on NB is presented. The results show that TIE increased as the mass of cells increased, meanwhile TRD decreased with the increase of cell mass. We observed an inverse correlation between TRD and cell mass. We demonstrate how to compute the maximum radiation dosage for cell death using the LT technique. Results show a possible blueprint for computing the TRD in vivo. The use of multiple cell ionization to determine radiation dosage along with better data accuracy concerning the tumor size and density will have profound implications for radiation dosimetry. The diminution in TRD becomes more significant in multiple cell ionization as we see in TRD vs the number of cells entering the trap. This is due to the chain effect generated by radiation and the absorption by water molecules at 1064 nm. This result provides us with better insight into the optimization of the therapeutic ratio.

Manipulation of Developmental Gamma-Globin Gene Expression: an Approach for Healing Hemoglobinopathies

β-Hemoglobinopathies are the most common monogenic disorders, and a century of research has provided us with a better understanding of the attributes of these diseases. Allogenic stem cell transplantation was the only potentially curative option available for these diseases until the discovery of gene therapy. The findings on the protective nature of fetal hemoglobin in sickle cell disease (SCD) and thalassemia patients carrying hereditary persistence of fetal hemoglobin (HPFH) mutations has given us the best evidence that the cure for β-hemoglobinopathies remains hidden in the hemoglobin locus. The detailed understanding of the developmental gene regulation of gamma-globin (γ-globin) and the emergence of gene manipulation strategies offer us the opportunity for developing a γ-globin gene-modified autologous stem cell transplantation therapy. In this review, we summarize different therapeutic strategies that reactivate fetal hemoglobin for the gene therapy of β-hemoglobinopathies.

Effect of Diabetes Mellitus on Sickle Hemoglobin Quantitation in Sickle Cell Trait

OBJECTIVES

We evaluated the effect of diabetes on sickle hemoglobin (HbS) measurement on two common clinical hemoglobin separation platforms.

METHODS

We performed a method comparison between the Bio-Rad Variant II high-performance liquid chromatography (HPLC) and Sebia Capillarys 2 Flex Piercing capillary electrophoresis (CE) using clinical specimens from 38 patients without hemoglobin variants and 57 patients with sickle cell trait (AS) (HbA1c%, 4.1%-15.4%). We investigated the effect of intermethod Hb% differences on result interpretation by a panel of expert clinical observers.

RESULTS

In diabetic specimens, HPLC undermeasured HbS% up to 7.4% vs CE, due to S1c eluting closely with A0 in HPLC. This increased concern for underlying α-thalassemia in diabetic patients with AS based on HPLC results. HPLC P2% was linearly related to HbA1c% and can be a screen for diabetic AS samples.

CONCLUSIONS

Glycosylation can interfere with HbS% measurement by HPLC. Susceptible specimens should be identified and preferentially analyzed via CE.

A Paper-Based Test for Screening Newborns for Sickle Cell Disease

The high cost, complexity and reliance on electricity, specialized equipment and supplies associated with conventional diagnostic methods limit the scope and sustainability of newborn screening for sickle cell disease (SCD) in sub-Saharan Africa and other resource-limited areas worldwide. Here we describe the development of a simple, low-cost, rapid, equipment- and electricity-free paper-based test capable of detecting sickle hemoglobin (HbS) in newborn blood samples with a limit of detection of 2% HbS. We validated this newborn paper-based test in a cohort of 159 newborns at an obstetric hospital in Cabinda, Angola. Newborn screening results using the paper-based test were compared to conventional isoelectric focusing (IEF). The test detected the presence of HbS with 81.8% sensitivity and 83.3% specificity, and identified SCD newborns with 100.0% sensitivity and 70.7% specificity. The use of the paper-based test in a two-stage newborn screening process could have excluded about 70% of all newborns from expensive confirmatory testing by IEF, without missing any of the SCD newborns in the studied cohort. This study demonstrates the potential utility of the newborn paper-based test for reducing the overall cost of screening newborns for SCD and thus increasing the practicality of universal newborn SCD screening programs in resource-limited settings.

Detection of Abnormal Hemoglobin Variants by HPLC Method: Common Problems with Suggested Solutions

Thalassemia and thalassemic hemoglobinopathies pose serious health problem leading to severe morbidity and mortality in Indian population. Plethora of hemoglobin variants is prevalent in multiethnic Indian population. The aim of the present study was to analyze laboratory aspects, namely, hematological profile and HPLC findings of the hemoglobin variants detected, and to discuss problems that we faced in diagnosis in a routine clinical laboratory. We screened a total of 4800 cases in a hospital based population of North India in a 2-years period of by automated HPLC method using the Variant Hemoglobin Testing System (Variant II Beta Thalassemia Short Program, Bio-Rad Laboratories) under the experimental conditions specified by the manufacturer. Whole blood in EDTA was used and red cell indices were determined using automated hematology analyzer. We detected 290 cases with abnormal variants in which beta thalassemia was the most common followed by hemoglobin E. Here, we discuss the laboratory aspects of various hemoglobin disorders and diagnostic difficulties in cases like borderline HbA2 values, presence of silent mutation, alpha thalassemia gene, and few rare variants which at times require correlation with genetic study. Special attention was given to HbA2 level even in presence of a structural variant to rule out coinheritance of beta thalassemia gene.

Lack of precision in HbA(1c) values on variant II in cases of hemoglobin Q India

This study was carried out to check the precision of HbA(1c) values on Bio-Rad Variant II in cases of a rare hemoglobin variant Q India. The study was carried out over a three month period on samples collected for HbA(1c) estimation. Seven out of eleven patients showed variable results of HbA(1c) with a very high and unacceptable intraday mean coefficient of variation (CV) of 9.93%. We conclude, that the results of HbA(1c) on Variant II can not be reported without adversely affecting HbA(1c) as a marker of long-term glycemic control in patients who have hemoglobin Q India. The HbA(1c) value of these patients needs to be assessed by a different instrument/method or the glycemic control be monitored by an alternate test like serum Fructosamine.

Direct laser trapping for measuring the behavior of transfused erythrocytes in a sickle cell anemia patient

Using a laser trap, we have studied the properties of erythrocytes from a sickle cell anemia patient (SCA) after receiving an intravenous blood transfusion, and a normal adult individual carrying normal adult hemoglobin. The hemoglobin type and quantitation assessment was carried out by high performance liquid chromatography (HPLC). We conducted an analysis of the size distributions of the cells. By targeting those erythrocytes in the overlapping regions of size distributions, we have investigated their properties when the cells are trapped and released. The efficacy of the transfusion treatment is also studied by comparing the relative changes in deformation and the relaxation-time of the cells in the two samples.

Modulating Effect of the -158 γ (C→T) Xmn1 Polymorphism in Indian Sickle Cell Patients

Xmn1 polymorphism is a known factor, which increases fetal haemoglobin production. Among the inherited disorders of blood, thalassaemia and Sickle Cell Diseases contributes to a major bulk of genetic diseases in India. Our aim was to verify the role of the Xmn1 polymorphism as a modulating factor in sickle cell patients and frequency of the polymorphism in Indian sickle cell patients. 60 sickle homozygous and 75 sickle beta thalassemia patients were included and 5 ml blood sample was collected from them. Screening of sickle patients was done by HPLC. An automated cell analyzer SYSMEX (K-4500 Model) was used to analyze the Complete Blood Count of patients. Xmn1 polymorphism analysis was done by PCR-RFLP and one-way ANOVA test was applied to analysis of variance between groups. Among the sickle patients 27 were heterozygous (+/−) and 19 were homozygous (+/+) while 30 were heterozygous (+/−) and 24 were homozygous (+/+) in sickle β-thalassemia patients. Extremely significant differences (p-value <0.001) of hematological parameters seen among patients with Xmn1 carrier and without the Xmn1 carrier. In our cases the clinical symptoms were barely visible and higher HbF level with Xmn1 carriers were found. Presence of Xmn1 polymorphism in sickle cell patients with higher HbF were phenotypically distinguished in the sickle cell patients. We conclude that the phenotypes of Indian sickle cell patients were greatly influenced by Xmn1polymorphism.

The first use of EaeI restriction enzyme in DNA diagnosis of Hb Q-India

INTRODUCTION

The α-chain variant Hb Q-India (c.193G>C) is caused by a point mutation GAC→CAC at codon 64 of the α1 globin gene and is clinically silent. Point mutations can be diagnosed easily by many simple polymerase chain reaction (PCR) techniques including PCR-restriction digest, but for Hb Q-India the restriction digest has never been described. In this work we aimed to develop a restriction enzyme digestion assay for DNA diagnosis of Hb Q-India, in order to increase the panel of restriction enzymes used in DNA diagnosis of haemoglobinopathies and also as a simple cheap alternative to the ARMS-PCR method.

METHODS

A restriction enzyme digestion assay was designed for diagnosis of Hb Q-India using the restriction enzyme EaeI enzyme as the Hb Q-India mutation abolishes the recognition site of this enzyme. Patients were screened for an abnormal haemoglobin by high performance liquid chromatography (HPLC) and those had an abnormal peak with a retention time between 4.7 and 4.8 minutes were selected for diagnosis at the molecular level. The α1 globin gene was amplified in 12 cases with a presumed diagnosis of Hb Q-India by HPLC and isoelectric focusing (IEF), and the amplified products were subjected to the EaeI digestion.

RESULTS

All the 12 cases were diagnosed positive (100%) for Hb Q-India by the EaeI restriction enzyme digest. They were heterozygotes for the mutation.

CONCLUSION

EaeI restriction enzyme digestion can be used as a simple and robust alternative method to ARMS-PCR for DNA diagnosis of Hb Q-India. The EaeI restriction enzyme can be added to the panel of restriction enzymes used in the DNA diagnosis of the abnormal Hb variants. Concomitant use of HPLC and IEF can be used efficiently for presumed diagnosis of this rare variant.

High performance liquid chromatography (HPLC): a simple method to quantify Hb C, O-Arab, Agenogi and F

Differentiation of some abnormal haemoglobins, such as Hb C, O-Arab, Agenogi, E, O-Indonesia, C-Harlem, and Siriraj, is difficult and quantitation of the various fractions is impossible with cellulose acetate electrophoresis. The authors report 13 cases of Hb C, 10 of Hb O-Arab and 5 of Hb Agenogi whose haemoglobin fractions were quantitated by HPLC during a thalassaemia screening programme. Hb F was determined by both Betke's method and HPLC. Analysis of data by linear regression demonstrates that the methods furnish overlapping results. Our findings show that HPLC is a rapid and easily reproduced method which allows quantitative and qualitative discrimination of the various haemoglobin fractions, making it a valid tool in screening programmes for haemoglobinopathies.

Hemostatic and thrombotic markers in patients with hemoglobin E/beta-thalassemia disease

Increased frequency of thrombosis has been observed in patients with hemoglobin E/beta-thalassemia (Hb E/beta-thal) disease, particularly those who have previously been splenectomized. We compared various hemostatic and thrombotic markers in blood from 15 Hb E/beta-thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin-antithrombin, beta2 thromboglobulin, C-reactive protein, tissue plasminogen activator antigen were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 were significantly higher in the S than in the NC group. Levels of plasminogen activator inhibitor-1 antigen were significantly higher in the S than in the NS group. Levels of protein C, protein S, antithrombin, and fibrinogen were significantly lower in the S and NS groups than in the NC group. Plasma lipoprotein(a) levels in the S and NS groups were not statistically different from NC. Our findings indicated that there is evidence of chronic low-grade coagulation and platelet activation, chronic low-grade inflammation, endothelial cell injury, impaired fibrinolysis, and decreased naturally occurring anticoagulants in splenectomized Hb E/beta-thal patients. These changes may account for the increased risk of thrombosis in these patients.

Electrospray mass spectrometric characterization of hemoglobin Q (Hb Q-India) and a double mutant hemoglobin S/D in clinical samples

OBJECTIVES

The clinical analysis of hemoglobin by ion exchange chromatography can result in ambiguities in identification of the nature of the globin chain present in patient samples. LC/ESI-MS provides rapid and precise determination of globin chain masses.

DESIGN AND METHODS

Hemolysate of hemoglobin Q-India and hemoglobin S/D/F have been analyzed using ESI-MS. Tandem-MS has been used to establish mutation in alpha chain of hemoglobin Q.

RESULTS

The identification of hemoglobin Q-India is readily achieved by LC/ESI-MS, which establishes the presence of a mutant alpha chain differing in mass from normal alpha chain by 22 Da. The site of mutation has been identified by tandem-MS analysis of a tryptic fragment encompassing residues alphaV62-K90. LC/ESI-MS screening has also provide an example of simultaneous occurrence of mutant globin chains containing beta6E-->V (Hb S, sickle) and beta121E-->Q (Hb D) variant. Expression of gamma(G) globin chain is also demonstrated in this sample.

CONCLUSIONS

The site of mutation in hemoglobin Q-India is identified as alpha64D-->H which differs from mutations alpha74D-->H in Hb Q-Thailand and alpha75D-->H in Hb Q-Iran. Mass spectrometric analysis of hemoglobins from a patient and her parents suggests inheritance of mutant beta globin genes from both parents.

A new method for the measurement of cerebral blood volume and total circulating blood volume using near infrared spatially resolved spectroscopy and indocyanine green: application and validation in neonates

A new technique known as tissue dye densitometry (TDD) has been developed to simultaneously measure cerebral blood volume (CBV) and total circulating blood volume (TCV) using near infrared (NIR) spatially resolved spectroscopy (SRS) and the injection of indocyanine green (ICG). Using a medical NIR spectrometer with SRS capability (NIRO-300, Hamamatsu KK), a new parameter is calculated known as the ICG Hb index (IHI), which represents the ratio of ICG concentration to Hb concentration in tissue. Acting as a tracer, ICG is cleared by the liver over 15 min, providing a change of tracer concentration (DeltaCICG,tis), which allows the calculation of the total Hb concentration in tissue (tcHb) using the equation: tcHbtis (micro molar) = DeltaCICG,tis/DeltaIHI. The CBV can subsequently be calculated from tcHbtis given the absolute Hb concentration in blood (g/dL), from which the ICG concentration in blood (DeltaCICG,bl) is obtained. By back-extrapolating the DeltaCICG,bl curve to the peak time, the initial ICG concentration in tissue blood (C0ICG,bl) can be found and TCV can then be calculated. The TCV of 17 neonates were measured using the TDD technique and for comparison using the previously reported fetal Hb dilution technique (FHD). The mean TCV measured by the FHD and TDD techniques were 70.19 +/- 13.73 mL/kg and 70.80 +/- 32.54 mL/kg. The Bland Altman plot showed that the bias was 0.61 +/- 34.34 mL/kg and limits of agreement (2 SD) were -68.07 mL/kg and 69.30 mL/kg. The agreement is limited and the TDD technique needs further validation and development for use in a clinical environment.

Pulmonary arterial hypertension in previously splenectomized patients with beta-thalassemic disorders

Our aim was to study the cause and describe the clinical features of pulmonary arterial hypertension (PHT) in splenectomized beta-thalassemia (beta-Thal) patients. Ten splenectomized beta-Thal patients with systolic pulmonary artery (PA) pressure >30 mm Hg were evaluated by echocardiography, right-heart catheterization, and pulmonary angiography. Five of these patients later underwent hemodynamic studies. Echocardiography and pulmonary angiography on the 10 patients showed normal values of left ventricular systolic function and no findings of acute or chronic pulmonary embolism. Hemodynamic evaluation showed very high PA pressures associated with markedly increased pulmonary vascular resistance indices (PVRIs). Hematological evaluation of the 10 patients showed marked anemia, markedly increased numbers of nucleated red blood cells (nRBCs), and serum ferritin. Mean platelet count, plasma beta2 thromboglobulin, and thrombin-antithrombin III complex levels were significantly increased. It was concluded that PHT can be found in splenectomized beta-Thal patients. Features associated with PHT were female sex, hemoglobin E/beta-Thal, status many years postsplenectomy, marked anemia, markedly increased nRBC count, thrombocytosis, and very high serum ferritin levels. PHT was not due to pulmonary emboli. Our findings suggested that severe PHT was due to increased PVRI from thrombotic pulmonary arteriopathy, likely from chronic low-grade hypercoagulability and platelet activation after splenectomy.

In vivo platelet activation and hyperaggregation in hemoglobin E/beta-thalassemia: a consequence of splenectomy

Patients with hemoglobin E/beta-thalassemia (E/beta-Thal) who have undergone splenectomy are prone to thrombosis in the small pulmonary arteries. To study the role of platelets in this situation, we assayed plasma beta2-thromboglobulin (betaTG) and performed whole blood platelet aggregation analysis of 30 E/beta-Thal patients, half of whom had undergone splenectomy. We compared results with those obtained with 15 healthy control subjects. Plasma betaTG levels in splenectomy patients were significantly higher than in control subjects and patients who had not undergone splenectomy, and platelets in splenectomy patients exhibited hyperaggregation in response to adenosine diphosphate, thrombin, and ristocetin. Levels of plasma thrombin-antithrombin III complex were also significantly higher. This finding is likely due to an increased number of erythrocytes with exposed phosphatidylserines, an effect that has been associated with splenectomy. The increased presence of thrombin in the blood may well be the cause of platelet hyperactivity, which was evident only in the asplenic patients Platelet hyperactivity very likely plays a pathogenetic role in the thrombosis of small pulmonary arteries that occurs in E/beta-Thal patients who have undergone splenectomy.

Hb Trento: an elongated C-terminal beta chain due to a new frameshift mutation [beta144 (-A)]

An elongated C-terminal hemoglobin variant, due to the deletion of nucleotide A in codon 144 (nucleotide 63600 GenBank entry UO1317) was found in a 31-year-old woman from Trento (northeastern Italy). This deletion led to the replacement of lysine at beta144 by a serine residue, the disappearance of the stop codon at position 147, and the presence of 12 additional residues, identical to those observed in Hbs Saveme, Tak and Cranston, which result from a similar mechanism. Hb Trento, amounting to 29% of the total hemoglobin, was unstable and had, as the other variants of this group, an increased oxygen affinity. It led to a mild compensated hemolytic anemia with red cell inclusion bodies. Functional studies of the isolated abnormal hemoglobin were difficult to perform because of autoxidation, precipitation, and formation of hybrids with Hb A.

Relationship between hypercoagulable state and erythrocyte phosphatidylserine exposure in splenectomized haemoglobin E/beta-thalassaemic patients

Small pulmonary arterial thromboses can occur following splenectomy of patients with haemoglobin E/beta-thalassaemia (Hb E/beta-thal). We compared plasma markers of coagulation activation in vivo and red blood cell (RBC) markers of procoagulant activity in 15 Hb E/beta-thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin-antithrombin III complex (TAT) were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 (F 1.2) were significantly higher in the S than in the NC group. Diluted Russell's viper venom clotting times were significantly shorter when RBCs from group S patients were added to the assay compared with RBCs from the NC group. Phosphatidylserine (PS) expression (% of annexin V-positive RBCs) on the outer leaflet of RBC membrane of both 'larger'- and 'smaller'-sized RBCs was significantly higher for the S than the NC group. The RBC PS expression of the S and the NS groups, respectively, accounted for 25 x 3% (P = 0 x 174) and 6.3% (P = 0 x 675) of the variation in plasma TAT levels. Our findings indicated that, when compared with NC, splenectomized patients with Hb E/beta-thal were in a chronic low-grade hypercoagulable state associated with increased numbers of circulating PS exposed RBCs. This condition may have a role in the risk of these patients for pulmonary arterial thromboses.

Clinical and hematological features of beta(+)-thalassemia (IVS-1 nt 5, G-C mutation) in Thai patients

Seventy-eight patients with IVS-1 nt 5, G-C, which is the common mutation of beta+-thalassemia found in the southern part of Thailand, were studied to determine whether it is possible to predict phenotypic severity from genetic factors. The clinical phenotype of homozygotes for IVS-1 nt 5, G-C and compound heterozygotes for IVS-1 nt 5, G-C and beta(0) - or beta(+)-thalassemia were variable and could not be accurately predicted. The associations between concomittant alpha-thalassemia or Hb CS or the presence of XmnI-Ggamma polymorphism and a mild clinical phenotype are not apparent, indicating the involvement of other ameliorating determinants or genetic modifications.

Genetic epidemiology of HbS in Oman: multicentric origin for the betaS gene

On the basis of a sample of 117 chromosomes, we have demonstrated the multicentric origin of the sickle mutation in Northern Oman. Three major haplotypes coexist: 52.1% Benin (typical and atypicals), 26.7% Arab-India, and 21.4% Bantu. These haplotypes are not autochthonous to Oman but originated elsewhere and arrived in Oman by gene flow. The distribution of haplotypes is in excellent agreement with the historical record, which establishes clear ancient contacts between Oman and sub-Sahara west Africa and explains the presence of the Benin haplotype; contacts with Iraq, Iran, present-day Pakistan, and India explain the presence of the Arab-India haplotype. More recent contacts with East Africa (Zanzibar/Mombasa) explain the presence of the Bantu haplotype. The pattern of the Arab-India haplotype in the populations of the Arabian peninsula reinforces the hypothesis that this particular mutation originated in the Harappa culture or in a nearby population and in addition reveals that the Sassanian Empire might have been the vehicle by which this Indo-European sickle mutation migrated (gene flow) to the present-day Arabian peninsula, including Oman.

Diagnosis of Hemoglobinopathies by High-Performance Liquid Chromatography

This report describes a unique cation exchange high-performance liquidchromatography capable of separating more than 40 frequently encountered human hemoglobins and variants within 12 min. Some of these variants are unresolvable by the conventional electrophoretic methods and would thus lead to an incorrect diagnosis of hemoglobinpathy. The method provides high sensitivity, superior resolution and accurate quantitation of hemoglobin concentrations. It can also be fully automated thus make it an ideal methodology for the diagnosis of hemoglobin disorders in a routine clinical laboratory.

Cation-exchange HPLC evaluated for presumptive identification of hemoglobin variants

A battery of relatively simple tests allows the presumptive identification of hemoglobin (Hb) variants, making unnecessary structural analysis by protein chemistry methods or DNA sequencing. The primary step in this strategy involves the use of a matrix of electrophoretic mobilities obtained under various experimental conditions. This leads to an unambiguous result in ∼90% of the cases. Additional tests are required to characterize with more confidence the remaining 10%. We describe here the use of cation-exchange HPLC on the Bio-Rad Variant automated analyzer with the “β Thalassemia Short” program. By comparing the elution time of 125 human Hb mutants, we found that some variants with almost identical pI values or produced by the same type of amino acid substitution displayed different elution times. We present several examples in which use of the HPLC profile helped establish the diagnosis.

Evaluation of high performance liquid chromatography for routine estimation of haemoglobins A2 and F

AIMS

To compare high performance liquid chromatography (HPLC) with conventional methods for the estimation of blood haemoglobin A2 (HbA2) and haemoglobin F (HbF) concentrations in routine thalassemia screening.

METHODS

An HPLC system (the VARIANT Hemoglobin Testing System) was tested for precision and reproducibility in the measurement of HbA2 and HbF, and reference ranges were obtained for a local healthy adult population. HPLC was compared with column anion exchange chromatography for HbA2 measurement, and radial immunodiffusion, or alkaline denaturation for HbF measurement. The reliability of HbA2 measurement by HPLC for the detection of beta thalassaemia and HbE was assessed in 200 consecutive samples for routine thalassaemia screening.

RESULTS

HPLC was rapid, technically easy, and gave good precision and reproducibility. In all comparisons linear regression analysis showed good correlation between HbA2 or HbF concentrations determined by HPLC and by the respective conventional methods. All beta thalassaemia or haemoglobin E carriers presumptively identified by conventional methods in 200 consecutive samples were detected by HbA2 measurement using HPLC, without any false positive or false negative results.

CONCLUSIONS

The measurement of HbA2 and HbF by HPLC is rapid, reproducible, and precise. It is as reliable as column chromatography for the measurement of HbA2 and radial immunodiffusion or alkaline denaturation for the measurement of HbF. HPLC may be an appropriate method for rapid screening in population surveys for beta thalassaemia and HbE carriers.

A new alpha chain variant Hb Tonosho [alpha 110(G17)Ala----Thr]: subunit dissociation during cation exchange chromatography for Hb A1c assay

A new alpha chain variant, alpha 110(G17)Ala----Thr, was detected because of subunit dissociation during the determination of the Hb A1c by automated cation exchange high performance liquid chromatography. The abnormal hemoglobin overlapped the cathodic edge of the band of Hb A in isoelectrofocusing. It was slightly unstable in the isopropanol test and had a slightly increased oxygen affinity. The abnormal alpha chain eluted slightly faster than the normal alpha chain in reversed phase high performance liquid chromatography. The amino acid substitution was determined by purification of S-alkylated alpha T-12,13 tryptic peptide, chymotryptic digestion, and sequencing of an octapeptide alpha 110-117. The abnormal alpha chain comprised about 14% of the total alpha chain. A biosynthetic study did not suggest selective loss of the abnormal chain in reticulocytes.

Hb Miyano or alpha 41(C6)Thr----Ser: a new high oxygen affinity alpha chain variant found in an erythremic blood donor

An abnormal hemoglobin found in an erythremic blood donor was separable only by isoelectrofocusing, where it was located at the cathodic edge of Hb A. Cation exchange high performance liquid chromatography of a tryptic digest from the total alpha chain revealed splitting of the alpha T-6 peak, although our routine procedures failed to uncover the abnormality. This enabled the chemical characterization and quantitation of the abnormal hemoglobin as alpha 41(C6)Thr----Ser comprising about 30% of the total hemoglobin. The purified hemoglobin showed increased oxygen affinity, decreased subunit cooperativity and effect of organic phosphates, and normal Bohr effect.

Hb Moriguchi or alpha 2 beta 2(97) (FG4)His---Tyr substitution at the alpha 1-beta 2 interface

An abnormal profile of cation exchange high performance liquid chromatography for the determination of Hb A1c led to the discovery of a new hemoglobin variant with a His----Tyr substitution at position 97(FG4) of the beta chain. The variant comprised about equal proportion to normal Hb A. It showed an increased oxygen affinity, normal n value and slightly reduced alkaline Bohr effect. However, the magnitude of the functional deviation is less than that of other variants with substitutions at the same position, and the heterozygous carrier was not erythremic.

Quantification of hemoglobin A2 and identification of hemoglobin variants using a fully automated hemoglobin analyzer

The DIAMAT Analyser System is a fully automated high performance liquid chromatographic (HPLC) instrument originally designed for the quantification of glycated hemoglobin (HbA1c). Buffers were developed for the separation and quantification of hemoglobin A2 on the DIAMAT. Also studied were the retention patterns of various hemoglobin variants on the DIAMAT using the buffers developed for the hemoglobin A2 quantification.

Separation of hemoglobins and hemoglobin chains by high-performance liquid chromatography

This paper evaluates various high-performance liquid chromatographic (HPLC) procedures useful for the detection and evaluation of numerous hemoglobin abnormalities in adults and in newborn infants. Two major approaches are discussed. The first concerns the analyses of hemoglobins in red cell lysates by anion- and cation-exchange chromatography; this type of HPLC has great potential in a routine laboratory, as quantitative data for numerous abnormalities can readily be obtained. The second concerns the separation of globin chains by reversed-phase HPLC that is most useful for the identification of hemoglobinopathies in adults, newborns, and fetuses.

Hyperunstable hemoglobin Toyama [alpha 2 136(H19)Leu----Arg beta 2]: detection and identification by in vitro biosynthesis with radioactive amino acids

A previously reported case of congenital Heinz body anemia was reinvestigated. Heat denaturation, isopropanol testing, PCMB precipitation, isoelectricfocusing, and reversed phase high performance liquid chromatography on the red cell lysate from the patient gave either negative, or at most, questionable results. In vitro globin biosynthesis using peripheral blood with incorporation of 3H-leucine demonstrated the production of an abnormal alpha chain at the rate of about 1/3 that of the normal alpha chain. A substitution, alpha 136(H19)Leu----Arg, was elucidated by peptide mapping and radiosequencing of an abnormal tryptic peptide. The hemoglobin consisting of the abnormal alpha and normal beta chains eluted between Hb A2 and Hb A0 in anion exchange high performance liquid chromatography. It was barely detectable by this method, comprising less than 1/1000 of the amount of Hb A0, although it was produced at a level of 1/3 of that of HB A0 in terms of radioactivity. The daughter of the propositus was similarly afflicted and produced the same abnormal alpha chain. The son, who also produced the abnormal alpha chain, was essentially free from hemolytic manifestation. His red cells were microcytic and showed an alpha/beta synthetic ratio of over 2.

The estimation of Hb A2 in the presence of Hb C or Hb E by reverse phase high performance liquid chromatography

Although Hb-C may be separated from Hb A2 by some ion exchange methods, most will not separate Hb E and Hb A2. The delta chain can be readily separated from the beta C, beta E and beta O-Arab chains by reverse phase HPLC. Hence, reverse phase HPLC provides a means of quantitatively determining Hb A2 in the presence of Hb C, Hb E, and Hb O-Arab. The procedure, although not highly accurate, does permit the detection of increased Hb A2, for example, in beta-thal heterozygotes and, therefore, is applicable to other conditions (Hb C, Hb E, Hb O-Arab).

The effect of alpha-thalassemia on the level of hybrid hemoglobin variants in heterozygotes

The influence of a relative deficiency in alpha chain production on the amount of Hemoglobins Kenya, P-Nilotic, and Lepore was determined. The level of these hybrid hemoglobins in heterozygotes was correlated to various states of alpha chain deficiency by: 1) quantitation of the variants in blood samples and comparing these data with the number of alpha globin genes determined by gene mapping, 2) in vitro recombination experiments involving isolated non-alpha chains and normal alpha chains, and 3) in vitro heat stability analyses of the isolated hemoglobins. Hb Kenya, composed of normal alpha and gamma-beta hybrid chains, is heat labile, has a decreased ability to combine with alpha chains, and its level in heterozygotes is greatly decreased when a concomitant alpha-chain deficiency (alpha-thalassemia) is present. Such a posttranslational control mechanism was not observed for Hb Lepore, with normal alpha chains and delta-beta hybrid chains, and Hb P-Nilotic, with normal alpha chains and beta-delta hybrid chains. The latter two variants are heat stable, and their hybrid chains combine equally well as normal beta chains with normal alpha chains. Hb P-Nilotic is more heat stable than Hb A and its in vitro formation is increased over that of Hb S, and perhaps even Hb A, in conditions of severe alpha chain deficiency.

Hb Himeji or beta 140 (H18) Ala----Asp. A slightly unstable hemoglobin with increased beta N-terminal glycation

A fast-moving abnormal hemoglobin found in a diabetic patient was identified as beta 140 (H18) Ala----Asp. It comprised about 40% of the total hemoglobin. The beta N-terminal glycation in the abnormal hemoglobin was estimated to be 3 times as much as that in Hb A in the same blood sample. The abnormal hemoglobin was slightly unstable. Oxygen affinity of the stripped hemoglobin was decreased, but that of red cells from the carrier was slightly higher than normal because of the reduced effect of 2,3-diphosphoglycerate.

Hb Regina or alpha 2 beta 2 96(FG3)Leu----Val: a high oxygen affinity variant discovered by cation-exchange HPLC

Results are reported of studies of the hemoglobin from one member of a Canadian family with a mild erythrocytosis. This variant, which accounted for about 40% of the hemoglobin, could be separated from Hb A and Hb A2 by cation-exchange chromatography. Micro methodology allowed the characterization of a Leu----Val replacement at position beta 96(FG3). Hb Regina has an increased oxygen affinity, which adequately explains the hematological observations.