Hb Q India: is it always benign?

A Novel Association of HbQ India Trait with Sickle Cell Anemia: a New Insight in Hemoglobinopathies

HbQ India is a rare α-chain structural hemoglobinopathy usually asymptomatic and presents in the heterozygous form or co-inherited with β-thalassemia trait. Herein, we are reporting the third case of novel association of HbQ India with HbS trait hemoglobinopathy in a 30-year-old young male presented with chief complaints of yellowish discoloration of sclera since 5 years with raised serum bilirubin levels along with pedigree analysis of the family.

Clinico-Hematological Profile of Hb Q India: An Uncommon Hemoglobin Variant

Inherited hemoglobin disorders include thalassemias and structural variants like HbS, HbE, and HbD, Hb Lepore, HbD-Iran, Hb-H disease and HbQ India. HbQ India is an uncommon alpha-chain structural hemoglobin variant seen in North and West India. Patients are mostly asymptomatic and often present in the heterozygous state or co-inherited with beta-thalassaemia. This study was done in a tertiary care teaching hospital in North India over a period of 7 years among patients referred from antenatal and other clinics for screening of hemoglobin disorders. Complete blood count, peripheral blood smear examination and cation exchange high performance liquid chromatography (HPLC) was done to quantify various hemoglobins. HbQ India was diagnosed if the unknown variant hemoglobin was detected within the characteristic retention window. Of a total of 7530 patients screened, 31 (0.4%) were detected to have HbQ India. Of these, 25 (0.3%) patients had HbQ India trait and 6 (0.1%) patients had compound heterozygosity for HbQ India and Beta Thalassemia trait (HbQ India-BTT). All patients were clinically asymptomatic and were detected as part of the screening for hemoglobin disorders. Only two patients with HbQ India-BTT had hemoglobin less than 10 g/dL. In 25 patients with HbQ India trait, HbQ ranged from 13.6 to 24.4% and in 6 patients with HbQ India-BTT, HbQ India ranged from 7.4 to 9.0%. HbQ India is an uncommon structural hemoglobin variant. Although asymptomatic, it may cause diagnostic difficulty in the compound heterozygous state with beta thalassemia. HPLC provides a rapid, accurate and reproducible method for screening of this condition to identify and counsel individuals.

C-Window Peaks on CE-HPLC are Extremely Rare in Northern India, and Only Infrequently Represent HbC

Hemoglobin C (HbC, HBB:c.19G > A) is a structural variant that has been reported rarely from India. This was a retrospective review of all high performance liquid chromatography (HPLCs) submitted over a 14 year period to a tertiary care center in North India with an aim of finding hemoglobins that elute in the C-window. Of the 32,364 HPLCs screened, 6 cases showed peaks in the C-window. Of these 6 cases, only two cases contained hemoglobin C. These was one case each of HbC/β thalassemia and compound heterozygosity for HbC and HbD. There were 4 cases which showed very similar red cell indices and chromatograms with multiple peaks eluting in D-window, C-window and an additional peak with a retention time of 4.74 min. These four cases were compound heterozygous for an α chain variant HbQ-India and a β-chain variant HbD.

Scanning for α-Hemoglobin Variants by High-Resolution Melting Analysis

BACKGROUND

Definitive detection of hemoglobin (Hb) variants requires DNA sequencing. High-resolution melting (HRM) analysis of polymerase chain reaction (PCR) amplicons was applied to detect and discriminate among uncommon α-Hb variants found in Thailand.

METHODS

Uncommon suspected α-Hb variants observed in Hb typing were identified by sequencing of DNA from whole blood samples. Three pairs of PCR primers covering the mutation regions in the three α-globin exons then were used for PCR coupled with difference in HRM analysis to subtract out the concomitant melting profile of the normal allele in the heterozygous state.

RESULTS

DNA sequencing identified six heterozygous α-Hb variants, namely, Hb G-Waimanalo (HBA2: exon 2, codon 64 G>A), Hb J-Buda (HBA1: exon 2, codon 61 G>T), Hb Kurosaki (HBA2: exon 1; codon 7 A>G), Hb O-Indonesia (HBA1: exon 3 codon 116 G>A), Hb Q-India (HBA1:exon 2, codon 64 G>C), and Hb Q-Thailand (HBA1: exon 2 codon 74 G>C). Difference HRM analysis showed one temperature melting profile using exon 1 primer pair, four different profiles with exon 2 primer pair, and one profile with exon 3 primer pair.

CONCLUSIONS

PCR-HRM analysis was effective in detecting and discriminating among single point mutations causing six uncommon α-Hb variants in heterozygous individuals. The method can be applied for routine screening due to its simplicity and relatively low cost.

HbD Punjab/HbQ India Compound Heterozygosity: An Unusual Association

Background

Haemoglobinopathies are the commonest hereditary disorders in India and pose a major health problem. Both beta thalassaemia and structural haemoglobin variants are relatively common in northwestern India. Here we report a 29-year-old Sindhi female who was referred to us for a haemoglobinopathy work up and genetic counseling since her spouse was a classical beta thalassaemia carrier.

Method

A complete blood count was done on an automated cell counter. Haemoglobin analysis was carried out using HPLC Variant Haemoglobin Testing System. The cellulose acetate electrophoresis was carried out [pH 8.9]. Confirmation of mutations was done by automated DNA sequencing.

Results

HPLC analysis showed four major peaks, HbA₀, a peak in the HbD window, an unknown peak [retention time 4.74 minutes] and a peak in the HbC window. The HbA₂ level was 2.2%, and the HbF level was 0.7%. Cellulose acetate electrophoresis at alkaline pH, a slow moving band was seen at the HbS/D position along with a prominent band at the HbA₂ position. DNA sequencing of the β and α genes showed presence of the two hemoglobin variants: Hb D [β 121GAA → CAA] and Hb Q [α 64 AAG → GAG]. The δ globin gene was normal. The additional peak in the HbC window was due to the formation of a heterodimer hybrid.

Conclusion

Both HbD Punjab and HbQ India are relatively common in India, but their co-inheritance has not been described in the country. This case is the third report of compound heterozygosity for HbQ India/HbD Punjab haemoglobinopathy globally and the second one from India.

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.

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.

Identification of hemoglobin Q India (alpha 1-64 Asp-His) through ARMS-PCR. First report from Pakistan

Various hemoglobinopathies have been reported from Pakistan excepting the rare ones like hemoglobin Q India. Our purpose of study was to identify the mutation (alpha 1 64 aspartate to histidine) through amplification restriction mutation system-polymerase chain reaction (ARMS-PCR) in patients where hemoglobin Q has been detected via high performance liquid chromatography (HPLC) and also to evaluate the cost effectiveness of the two technologies. All patients irrespective of age and gender who underwent HPLC for identification of their hemoglobin variant during January 1, 2006 to January 30, 2007 were studied. The blood samples with unknown peak at a retention time of 4.7 min were evaluated at the molecular level. Analysis of HPLC tracings of 11,008 subjects over a thirteen-month period identified ten individuals with hemoglobin Q. Male to female ratio was 1:1.5 and their age was variable ranging from 1 to 49 (mean 22.8) years. The mean hemoglobin level was 11.3 g/dl while MCV (fl) and MCH (pg) were 73.0 and 20.8 respectively. HPLC showed an unknown peak of 17.7% which was detected as Hb Q. ARMS based PCR showed Hb Q specific product of 370 bp and also an amplified product of 766 bp as the control fragment in these samples. This is the first ever report that documents the presence of Hb Q India (alpha 64 Asp to His) in Pakistani population. We recommend that HPLC be used as a useful screening tool especially in developing countries where PCR facilities may not be accessible.