False HbA1cValue due to a Rare Variant of Hemoglobin J-Cubujuqui.

BACKGROUND: Hemoglobin (Hb) J-Cubujuqui is a rare Hb variant, and reports about it are very limited. There are no descriptions that it affects the results of glycated Hb. METHODS: In this study, we describe a rare variant discovered during newborn screening. Both high-performance liquid chromatography (HPLC) and capillary electrophoresis for hemoglobin analysis displayed abnormal peaks. The Hb variant was confirmed by Sanger sequencing. RESULTS: The pedigree study shows the variant was inherited from the newborn's father. His fasting blood glucose (FBG) level was 5.5 mmol/L. HbA1c measured by HPLC was falsely low in her father (2.41%), whereas that measured by immunoassay was normal (5.11%). Sanger sequencing revealed a heterozygous mutation (CGT˃AGT) at amino acid position 141 of the α1 gene, corresponding to Hb J-Cubujuqui [α1 141(HC3) Arg→Ser (CGT˃AGT); HBA1:c.424C˃A (or HBA2)]. CONCLUSIONS: This is the first report that Hb J-Cubujuqui interferes with the measurement of HbA1cand prompts clinicians to pay attention to the accuracy of glycated Hb results.

Unexpected HbA1c results in the presence of three rare hemoglobin variants.

Hemoglobin (Hb) variants, characterized by structural abnormalities in the globin chains, are among the most common inherited disorders. It has been shown that Hb variant remains an important cause of erroneous HbA1c results. Thus, it is important to be aware of the extent of the interference of each Hb variant encountered to avoid reporting unreliable results. However, the effects of many types of Hb variants on the measurement of HbA1c remain unclear. Here, we describe three rare Hb variants, Hb J-Tashikuergan [HBA2: c.59 C > A], Hb Pyrgos [HBB: c.251G > A], and Hb Hope [HBB: c.410 G > A], which lead to extremely high values (>25%) determined by Variant II Turbo 2.0. We further investigated their effects on HbA1c measurement by an HPLC system (Bio-Rad D100), a CE system (Sebia Capillarys 3 TERA), a boronate affinity chromatography system (Premier Hb9210), and an immunoassay method (Roche Diagnostics), and found that these Hb variants severely interfered with HbA1c measurement by Variant II Turbo 2.0 and Bio-Rad D100. This study demonstrates that patients with abnormally high HbA1c levels should be highly suspected of carrying Hb variants. When the HbA1c results are considered unreliable, other indicators such as glycated albumin may be a possible alternative to HbA1c in diabetic patients.

Eleven Cases of Hb J-Paris-I [HBA2: c.38C>A (or HBA1)]: A Stable α Chain Variant Elutes in the P3 Window on High-Performance Liquid Chromatography.

Hb J-Paris-I [HBA2: c.38C>A (or HBA1)] is a stable fast-moving hemoglobin (Hb) that elutes in the P3 window on high performance liquid chromatography (HPLC). The mutation can happen on either the α1- or α2-globin gene. Codon 12 changes from GCC to GAC to replace the alanine amino acid with aspartic acid. This change is external with no clinical significance. The elution in the P3 wave on HPLC can interfere with the glycated Hb assay by HPLC. In this study, data of 11 cases of Hb J-Paris-I were thoroughly presented. The majority of the cases were of Indian ethnicity. The mean value of Hb J-Paris-I on HPLC was 26.7 ± 2.0%. The retention time (RT) was 1.75 ± 0.03 min. The isoelectric focusing (IEF) mean value was -5.6 (range -6.1 to -4.9). Hb A2 was consistently reduced to 1.8 ± 0.3%. A fraction of 0.8% corresponding to the Hb A2-J-Paris-I (α2J-Paris-Iδ2) is likely to be concealed within the A0 peak of Hb A on HPLC. Interestingly, two cases were associated with two different polymorphisms [HBA2: c.-24C>G or Cap +14 (C>G) and HBA2: c.*136A>G polymorphism] without apparent effect on the variant expression.

Fifteen Cases of Hb J-Meerut: The Rare Association with Hb E and/or HBA1: c.-24C>G (or HBA2) Variants.

Hb J-Meerut [HBA2: c.362C>A (or HBA1)] is a rare, stable, nonpathogenic α-globin gene variant that peaks in the area between the P3 and A0 windows on high performance liquid chromatography (HPLC). Few cases from different ethnic origins have been published but the majority were Asian Indians. Coinheritance with other hemoglobin (Hb) variants are rarer and can change the Hb J-Meerut phenotype making a diagnostic dilemma. In this study, we have reported 15 cases of Hb J-Meerut, discovered during a wide spectrum study of α-globin chain variants in the UK. The diagnosis was confirmed by forward and reverse DNA sequencing of the α1- and α2-globin genes. The average of the Hb J-Meerut expression was 20.9% of total Hb and characterized by a retention time (RT) of 1.9 min. (on average) on HPLC. The median of isoelectric focusing (IEF) was 5.6 mm above Hb A. Among the 15 cases studied, one case coinherited the Hb E (HBB: c.79G>A) mutation in heterozygosity and another case was associated with the Cap +14 (C>G) [HBA1: c.-24C>G (or HBA2)] variant. We noticed that the coinheritance of the Hb E mutation reduced the Hb J-Meerut expression with the formation of a hybrid peak missed on the HPLC chromatograph. We also noticed an increased expression of Hb J-Meerut in the case showing the coinheritance of the HBA2: c.-24C>G (or HBA1) variant.

Hematological and Molecular Findings in the First Case of Hb J-Norfolk [HBA2: c.173G>A (or HBA1] in an Indian Patient.

We here report a case of a 23-year-old female from Mumbai, Maharashtra, India who was detected to carry the α chain variant Hb J-Norfolk [HBA2: c.173G>A (or HBA1]. She had no clinical symptoms and was referred to us for routine investigations and screening. An abnormal peak was detected on both high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) with a fast-moving band on cellulose acetate electrophoresis. There is no detailed study on the HPLC and CE pattern of this hemoglobin (Hb) variant, and therefore, this study will help in detecting and avoiding missing these variants during routine investigations and population screening. This is the first report of this variant in the Indian population.

First Report of a Chinese Family Carrying a Double Heterozygosity for Hb Q-Thailand and Hb J-Bangkok.

The double heterozygosity for α and ß chain variants leads to the formation of abnormal heterodimer hybrids, which could render laboratory diagnostics in a routine setting difficult. The following is the first report of a double heterozygosity for Hb Q-Thailand [α74(EF3)Asp→His; HBA1: c.223G>C] with α+-thalassemia (α+-thal) and Hb J-Bangkok [ß56(D7)Gly→Asp; HBB: c.170G>A] found in a Chinese family. Both subjects were healthy with normal or borderline hematological parameters. Hemoglobin (Hb) analyses showed a novel variant, Hb Q-Thailand and Hb J-Bangkok. Family studies helped in the initial recognition and in making presumptive diagnoses, but definitive diagnoses of these cases with complex α and ß chain variants could only be obtained after DNA analysis.

[Effects of hemoglobin J-Bangkok traits on measurements of glycated hemoglobin by five methods].

OBJECTIVE: To evaluate the interference of hemoglobin variants J-Bangkok on glycated hemoglobin (HbA(1)c) detected by five measurement systems. METHODS: Seventy cases of blood samples were collected at Zhongshan Hospital of Sun Yat-sen University from July 2012 to January 2014, the blood samples were divided into the normal control group (40 cases) and Hb J-Bangkok variant group (30 cases), and the normal control group was divided into healthy control group (20 cases) and diabetic group (20 cases). HbA(1)c measurement systems were Primus Ultra2, Variant Ⅱ, Variant Ⅱ Turbo, Modular P and Leadman. Based on the standard of the American National Glycosylated Hemoglobin Standardization Program (NGSP), Primus Ultra2 was used as comparative system, and the other 4 systems were test systems. Comparative analysis and bias evaluation were conducted on the results from five detection systems in different groups, statistical analysis were used for evaluating the differences. The estimated average glucose (eAG) was calculated by HbA(1)c values and fasting plasma glucose (FPG) of Hb J-Bangkok variant group with the different detection systems. Deming regression analysis was used to determinate whether Hb J-Bangkok produced significant clinical effect on HbA(1)c results. HbA(1)c ± 10% and relative bias at 6% and 9% HbA1c were evaluation limits. RESULTS: The differences of the 95% confidence interval (95%CI) between the test systems and the comparative system in control group were within ±0.7% HbA(1)c, bias were less than 6%, there were no statistically significant difference (P>0.05). In Hb J-Bangkok group, the eAG calculated from HbA(1)c measured by using Primus Ultra2, Modular P and Leadman were (8.14±2.99), (8.10±3.06) and (8.23±3.00)mmol/L, which had no statistically significant difference compared with FPG ((8.21±3.12)mmol/L, t=0.996, 1.091, 1.479, all P>0.05), and the differences of 95%CI between the results measured by Modular P and the comparative system were all within ±0.7% HbA(1)c, bias were -4.3%-0.4% and -5.2%-4.9%, there were no statistically significant difference (P>0.05). At 6% and 9% HbA(1)c concentrations, the mean differences of the results from the three detection systems were less than the clinically acceptable range. These results showed that the systems of Primus Ultra2, Modular P and Leadman were not affected by Hb J-Bangkok. However, the eAG values calculated from HbA(1)c of Variant Ⅱ and Variant Ⅱ Turbo were (5.58±2.12) and(5.00±2.13)mmol/L, which showed statistically significant lower results compared with FPG level (t=12.29, 13.23 , all P<0.001). Compared with Primus Ultra2, the differences of 95%CI were outside of ± 0.7% HbA1c, bias were -31.9%--12.0% and -42.0%- -17.6% , greater than 6%, showed a negative bias.At 6% and 9% HbA(1)c concentrations, the mean differences of the results were all greater than the clinical acceptable range. These results indicated that Hb J-Bangkok had significantly clinical interference on Variant Ⅱ and Variant Ⅱ Turbo systems. CONCLUSION: Hb J-Bangkok has different interference on different HbA(1)c measurement systems, when performs the HbA(1)c test, clinical laboratory should pay attention to identify Hb variants, and select the appropriate methods to measure the HbA(1)c values in order to prevent the occurrence of interference by Hb variants.

A Mosaic Expression of a Hb J-Amiens (HBB: c.54G > T; p.Lys18Asn) and its Interference with Hb A1c Analysis.

We report the case of a 56-year-old Caucasian woman in whom hemoglobinopathy screening was triggered following an aberrant Hb A1c analysis. Preliminary diagnosis of the hemoglobin (Hb) variant was obtained through cation exchange high performance liquid chromatography (HPLC) and gel electrophoresis. DNA analysis confirmed the presence of Hb J-Amiens [ß17(A14)Lys→Asn; HBB: c.[54G > C or 54G > T)]. However, an unbalanced ratio between wild type and mutant signal after direct sequencing and a lower than expected percentage of this Hb variant led to the suggestion of a mosaic expression. Furthermore, different methods [capillary zone electrophoresis (CZE), cation exchange HPLC and boronate affinity] were tested to study the possible interference of this variant with Hb A1c measurements. These investigations showed a clinically relevant difference between the methods tested. Hb A1c analysis may lead to the discovery of new Hb variants or mosaicism for previously described Hb variants. This may have genetic consequences for the offspring of carriers and brings about the question of partner testing.

[Analysis of clinical phenotypes of compound heterozygotes of Hb J-Bangkok and ß-thalassemia].

OBJECTIVE: To analyze hematological characteristics of compound heterozygotes of Hb J-Bangkok and ß-thalassemia, and to explore the influence of Hb J-Bangkok on the phenotype of ß-thalassemia. METHODS: Peripheral blood samples from a patient carrying Hb J-Bangkok and a ß-thalassemia mutation, her family members and three sporadic Hb J-Bangkok carriers were collected. RBC analysis and hemoglobin electrophoresis were performed. Genotypes of α- and ß-globin genes were analyzed. RESULTS: The father of the proband and the three sporadic cases were single carriers of Hb J-Bangkok. All of them were asymptomatic and have normal hematological parameters except for an abnormal hemoglobin band detected on hemoglobin electrophoresis. The proband was a compound heterozygote for Hb J-Bangkok and ß-thalassemia mutation IVS-Ⅱ-654. She presented typical ß-thalassemia trait, featuring hypochromic microcytic anemia and increased Hb A2 level. An abnormal hemoglobin band was also detected. CONCLUSION: Carriers of Hb J-Bangkok alone are asymptomatic. Co-existence of Hb J-Bangkok and ß-thalassemia may not aggravate the phenotype. Therefore, couples with one carrying Hb J-Bangkok and another carrying a ß-thalassemia mutation do not require prenatal diagnosis.

Report of haemoglobin J-Toronto and alpha thalassemia in a family from North of Iran.

We report of an Iranian family with history of a rare haemoglobin variant, Haemoglobin J associated with alpha thalassemia, discovered while performing premarital thalassemia screening. In the present study we report the first case of haemoglobin J-Toronto [alpha 5 (A3) Ala > Asp] on -globin gene, found in a 16-year-old female from Mazandaran Province, North of Iran. Further investigation characterized the same mutation for mother and brother of the proband, whilst mother was also a carrier of an alpha thalassemia gene mutation (-alpha3.7). Haemoglobin J-Toronto was previously just reported from Canada and has not been found in any part of Iran.

Isolated Hb Providence ß82Asn and ß82Asp fractions are more stable than native HbA(0) under oxidative stress conditions.

We have previously shown that hydrogen peroxide (H(2)O(2)) triggers irreversible oxidation of amino acids exclusive to the ß-chains of purified human hemoglobin (HbAo). However, it is not clear, whether α- or ß-subunit Hb variants exhibit different oxidative resistance to H(2)O(2) when compared to their native HbAo. Hb Providence contains two ß-subunit variants with single amino acid mutations at ßLys82→Asp (ßK82D) and at ßLys82→Asn (ßK82N) positions and binds oxygen at lower affinity than wild type HbA. We have separated Hb Providence into its 3 component fractions, and contrasted oxidative reactions of its ß-mutant fractions with HbAo. Relative to HbAo, both ßK82N and ßK82D fractions showed similar autoxidation kinetics and similar initial oxidation reaction rates with H(2)O(2). However, a more profound pattern of changes was seen in HbAo than in the two Providence fractions. The structural changes in HbAo include a collapse of ß-subunits, and α-α dimer formation in the presence of excess H(2)O(2). Mass spectrometric and amino acid analysis revealed that ßCys93 and ßCys112 were oxidized in the HbAo fraction, consistent with oxidative pathways driven by a ferrylHb and its protein radical. These amino acids were oxidized at a lesser extent in ßK82D fraction. While the 3 isolated components of Hb Providence exhibited similar ligand binding and oxidation reaction kinetics, the variant fractions were more effective in consuming H(2)O(2) and safely internalizing radicals through the ferric/ferryl pseudoperoxidase cycle.

[Evaluation of Variant II analyzer equipped with the new 270-2101 NU kit (Bio-Rad) for HbA 1c assay]. / Evaluation de l'analyseur Variant II équipé de la nouvelle trousse 270-2101 NU (Bio-Rad) pour le dosage de l'HbA 1c.

HbA(1c) represents a key parameter in the follow-up of glycemic balance in diabetic patients. It may be assayed by different methods, among which high-pressure liquid chromatography (HPLC). We have evaluated a new method available on HPLC Variant II analyzer (BioRad) equipped with the new kit 270-2101 NU. Chromatographic separation is improved, allowing a better identification of peaks. Intra- and inter-assay coefficients of variation are respectively lower than 1.1% and 1.8%. Linearity is excellent from 3.2% to more than 18%. The correlation with the previous method (kit 270-2101) is good: y (% HbA(1c) new kit) = 0.944x (% HbA(1c) previous kit) + 0.299, r(2) = 0.995. There is no inter-sample contamination. This method is less sensitive to interferences frequently found in practice (labile glycated hemoglobin, carbamylated haemoglobin) than the previous one. Validation is possible in more circumstances when an abnormal hemoglobin is present (especially in case of hemoglobin D or E). As the control of analytic quality is a major element for validation and clinical use of HbA(1c) results, the characteristics of this new method make it a well-suited tool for daily laboratory practice.

[Evaluation of HbA1c using different methods in haemoglobin variant, Hb J-Bangkok].

A 31-year-old Japanese man with haemoglobin variant, Hb J-Bangkok [beta56 (D7) Gly-->Asp], was found by discrepant values between HbA1c and glycated-albumin. We measured HbA1c using three different methods, HPLC, enzyme assay and turbidimetric immunoassay. HbA1c value measured by HPLC was much lower than those by others. Furthermore, we estimated calculated glyco-haemoglobin value measured by high-resolution HPLC, revealing that HbA1c values measured by enzyme assay and turbidimetric immunoassay were comparable with calculated value. When measuring HbA1c value in haemoglobin variant, Hb J Bangkok, enzyme assay and turbidimetric immunoassay are useful methods.

Conundrum of elevated HbA1C and hypoglycemia-a rare cause.

A white diabetic patient on insulin therapy presented with recurrent hypoglycemia despite very high glycosylated hemoglobin (HbA1c) values. Hemoglobin (Hb) variants, chemically modified Hb, and abnormalities of red cell turnover cause errors in HbA1c measurement. Widely prevalent Hb variants affecting HbA1c estimation include HbS and HbC in African Americans, HbE in southeast Asians, and carbamyl-Hb in uremic patients. In addition, there are at least 893 other Hb variants as of 2005, many of which affect HbA1c estimation. HbA1c values are also affected by methodology of estimation. Our patient had HbJ, which is rare amongst whites. The relationship between HbA1c values and mean plasma glucose allows estimation of expected HbA1c. Significant discrepancy between expected and measured HbA1c should be evaluated. Considering Hb variants, evaluating for the same and estimating HbA1c with the appropriate method under such circumstances are described. Numerous new or rare Hb variants will be diagnosed if suspicion is appropriately entertained.

Evaluation of the Interference of Hemoglobin Variant J-Bangkok on Glycated Hemoglobin (HbA1c) Measurement by Five Different Methods.

Objective The interference of the hemoglobin variant (Hb J-Bangkok) was evaluated on 4 different glycated hemoglobin assays and compared with a reference immuno assay. Methods An overall test of coincidence of 2 least-squares linear regression lines was performed to determine whether the presence of Hb J-Bangkok caused a statistically significant difference in HbA1c results compared with a reference immuno assay. Statistical analysis was performed on the difference of the estimated average glucose calculated from HbA1c values and fasting plasma glucose in the Hb J-Bangkok variant group using the different detection systems. Deming regression analysis was used to determinate whether Hb J-Bangkok had a significant interference on HbA1c results using an HbA1c±10% relative bias at 6% and 9% HbA1c as evaluation limits. Results Turbidimetric inhibition immunoassay method, and enzymatic methods were not affected by Hb J-Bangkok. However, Hb J-Bangkok showed statistically significant interference to the two ion-exchange high-performance liquid chromatography methods. Conclusion When performing HbA1c tests, clinical laboratory personnel should identify the Hb variant and select the appropriate methods or use alternative indicators.

Determination of unique amino acid substitutions in protein variants by peptide mass mapping with FT-ICR MS.

Peptide mass mapping plays a central role in the structural characterization of protein variants with single amino acid substitutions. Among the 20 standard amino acids found in living organisms, 18, all but Leu and Ile, differ from each other in molecular mass. The mass differences between amino acids range from 0.0364 to 129.0578 Da. The mass of the mutated peptide or the difference between normal and mutated peptides uniquely determines the type of substitution in some cases, and even pinpoints the position of the mutation when the involved residue is found only once in the peptide. Among 75 pairs of amino acid residues that are exchangeable via a single nucleotide replacement, 53 show specific change in exact mass, while only 25 in nominal mass. On the other hand, precise measurement, at least to the third decimal place, greatly enhances the capacity of the peptide mass mapping strategy for structural characterization. This notion was verified by an analysis of three Hb variants using MALDI-FTICR MS. In addition, the baseline resolution of two 1 kDa peptides with a single amino acid difference, Lys or Gln, which have the smallest (0.0364 Da) difference among residues, was achieved by measurement at a mass resolving power of 342,000. The results indicated that the smallest difference, 0.0040 Da between [Delta29.9742 for Glu-Val] and [Delta29.9782 for Trp-Arg], among all types of amino acid substitutions derived from a single nucleotide replacement can be discriminated at the present performance level. Therefore, FTICR MS is capable of identifying all 53 types of substitutions, each of which is associated with a unique mass difference, except for the Leu and Ile isomers.

Beta thalassemia IVS-I-5(G-->C) heterozygosity masked by the presence of HbJ-Meerut in a Dutch-Indian patient.

We describe the genotype/phenotype correlation in a 35 year old anemic female referred to our laboratory because a fast eluting minor fraction on HPLC, mild hemolysis and hematological parameters suggesting a Thalassemia trait, eventually in combination with iron depletion. Direct sequencing of the alpha globin genes revealed heterozygosity for HbJ-Meerut, a Glu-->Ala substitution at residue 120 not justifying the hematological parameters. No other point mutations were found on the alpha genes and Gap-PCR excluded the 6 common deletion defects. Direct sequencing of the beta-globin genes revealed the IVS-I-5 (G-->C) transversion in absence of the elevated HbA2 levels usually measured in carriers of this beta-Thalassemia mutation. The HbA2 tetramer in the presence of HbJ-Meerut divides in two parts. One alphaN2/delta2 migrating on the right spot on HPLC. The other alphaJ2/delta2 migrating under the HbA fraction. Classic alkaline electrophoresis and the modern capillary electrophoresis CE showed these two tetramers and the reduction of the elevated HbA2 level of the beta-Thalassemia trait by at least 20% due to HbA2 Meerut.

Haemoglobin J-Baltimore can be detected by HbA1c electropherogram but with underestimated HbA1c value.

Glycated haemoglobin (HbA(1c)) is considered the gold standard for assessing diabetes compensation and treatment. In addition, fortuitous detection of haemoglobin variants during HbA1c measurement is not rare. Recently, two publications reported different conclusions on accuracy of HbA(1c) value using capillary electrophoresis method in presence of haemoglobin J-Baltimore (HbJ).Here we describe the fortuitous detection of unknown HbJ using capillary electrophoresis for measurement of HbA(1c). A patient followed for gestational diabetes in our laboratory presented unknown haemoglobin on Capillarys 2 Flex Piercing analyser which was identified as HbJ. HbJ is not associated with haematological abnormalities. High Performance Liquid Chromatography methods are known to possibly underestimate HbA(1c) value in the presence of this variant. This variant and its glycated form are clearly distinguished on electropherogram but HbJ was responsible for underestimating the true area of HbA(1c). Capillary electrophoresis is a good method for detecting HbJ but does not seem suitable for evaluation of HbA(1C) value in patients in presence of HbJ variant.