The Interactions of α -Thalassemia with Hemoglobinopathies

Transcranial Doppler Ultrasound in Peninsular Arab Patients With Sickle Cell Disease

OBJECTIVES

Transcranial Doppler ultrasound is used to identify patients with sickle cell disease (SCD) at risk for stroke. We performed transcranial Doppler studies in patients from 4 countries in the Arabian Peninsula (Kuwait, Oman, Iraq, and United Arab Emirates) to document the prevalence of abnormal transcranial Doppler findings.

METHODS

The patients were recruited from outpatient clinics and studied in a steady state. Transcranial Doppler examinations were performed with standard equipment by experienced operators. The time-averaged maximum mean velocity (TAMMV) was documented in the arteries of the circle of Willis. The hemoglobin (Hb) genotype was confirmed, and the fetal Hb level and complete blood counts were determined.

RESULTS

There were 415 patients in the study, aged 2 to 18 years (mean ± SD, 8.6 ± 3.5 years). None of the patients had an abnormal TAMMV (ie, > 200 cm/s), whereas only 13 (3.1%), all from Iraq, had conditional values (170-200 cm/s) in the right middle cerebral artery and 7 (1.7%) in the left middle cerebral artery. There were no consistent TAMMV differences among male and female patients or in patients with different Hb genotypes (sickle cell anemia, sickle cell β^0- thalassemia, and sickle D). The use of hydroxyurea was associated with a lower TAMMV, whereas a blood transfusion history had no influence. Total hemoglobin, reticulocyte count, serum bilirubin, and fetal Hb values showed varying degrees of association with the TAMMV in the different vessels.

CONCLUSIONS

This study has demonstrated the rarity of abnormal transcranial Doppler findings among Peninsular Arab patients with SCD. The guidelines for transcranial Doppler screening in this population need further studies and recommendations.

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.

The range of hemoglobin A(2) in hemoglobin E heterozygotes as determined by capillary electrophoresis

Capillary electrophoresis (CE) is capable of distinguishing hemoglobin E (HbE) from hemoglobin A(2) (HbA(2)), thus permitting quantification of HbA(2) in patients with HbE. In this study, routine samples submitted for evaluation of hemoglobinopathy that demonstrated HbE were studied by high-pressure liquid chromatography and CE. The data for 52 samples from adult HbE heterozygotes were compared with those for a control group consisting of 209 patients. The mean HbA(2) of patients with HbE trait was 3.4% (SD, 0.4%), which was significantly higher (P < .001) than the 2.6% (SD, 0.4%) for the control group. Seven samples from adults homozygous for HbE were also evaluated. The mean HbA(2) of HbE homozygotes was 4.4%, which was significantly greater (P < .001) than the HbA(2) values for the HbE heterozygotes. Data from these cases provide an estimate of the range of HbA(2) in patients with HbE when evaluated by CE.

Usefulness of brilliant cresyl blue staining as an auxiliary method of screening for α-thalassemia

Hemoglobin (Hb) electrophoresis is widely used in thalassemia screening. Most Hb variants express a specific abnormal band on the cellulose acetate membrane. The technique is useful in the diagnosis of the type of thalassemia but is not sensitive enough to detect alpha-thalassemia minor because the quantity of the HbH is too small to be expressed on the supporting medium. We used simple staining of blood smears rather than the sophisticated molecular method to detect HbH inclusions. To evaluate the effectiveness of this method, we used brilliant cresyl blue (BCB) staining of red blood cells in 509 patients with microcytosis and erythrocytosis caused by various conditions. The results indicate that BCB staining is useful in the identification of subjects who possess alpha-thalassemia traits. Coexisting conditions such as beta-thalassemia and iron-deficiency anemia did not affect the detection of the HbH inclusions with the use of BCB staining. We conclude that BCB staining is helpful and reliable as an auxiliary method of detecting HbH inclusions in the diagnosis of alpha-thalassemia traits, especially in places where medical resources are limited.

alpha-Thalassemia 2, 3.7 kb deletion and hemoglobin AC heterozygosity in pregnancy: a molecular and hematological analysis

alpha-Thalassemia is a synthesis hemoglobinopathy with a worldwide distribution. alpha-thalassemia-23.7kb (alpha-Thal23.7kb) was investigated by PCR and standard hematologic analysis techniques in 106 pregnant women - 53 heterozygous for hemoglobin (Hb) A and C (AC) and 53 homozygous for the normal Hb A (AA) with similar ages and race ancestry. Eleven (21%) of AC women were alpha-Thal23.7kb heterozygous and 1 (2%) was homozygous, while 12 AA women (23%) were heterozygous. In the AA group, the MCV differed among those with normal alpha genes and those with alpha-Thal23.7kb (P = 0.031). Statistical analysis of AC group patients with normal alpha genes and alpha-Thal23.7kb carriers showed differences in MCV (P = 0.001); MCH (P = 0.003) and Hb C concentrations (P = 0.011). Analysis of AA and AC group patients with normal alpha genes showed differences in RBC (P = 0.033), Hb concentration (P = 0.003) and MCHC (P < 0.0001). There were no statistically significant differences for any hematologic parameters between AC and AA group patients with the alpha-Thal23.7kb genotype. The AC alpha-Thal23.7kb homozygous women had low hematologic parameters. Serum ferritin levels were normal among the groups studied. These results emphasize the importance of diagnosis and follow-up of patients with hemoglobinopathy carriers during pregnancy in order to administer adequate therapy and avoid further complications for mothers and newborns.

Capillary isoelectric focusing and high-performance cation-exchange chromatography compared for qualitative and quantitative analysis of hemoglobin variants

We have developed two assays for complete analysis of hemoglobins (Hbs) in the field of hemoglobinopathies: a high-performance cation-exchange liquid chromatography (HPLC) assay on the weak cation-exchanger Poly Cat A and a two-step capillary isoelectric focusing (CIEF) assay on the neutral-coated capillary from Beckman in a narrow pH gradient. The resolution was satisfactory for both HPLC and CIEF and allowed separation of normal and common abnormal Hbs, i.e., Hb A, Hb F, Hb A2, Hb S, Hb C, and Hb E; slight differences were shown for the resolution of unusual variants such as Hb C-Harlem and Hb D-Punjab. The reproducibility of retention times was satisfactory as well for HPLC (CV 3.3%) and CIEF (CV 4.9%). The imprecision of quantification of Hb A2, evaluated at two concentrations, and of Hb F and Hb S was &lt;5%, except for low concentrations of Hb A2quantified by CIEF. Quantitative data obtained for these three Hb forms were highly correlated between the two assays. These results suggest that the new CIEF assay can be competitive with HPLC for complete routine analysis of Hb variants.

Cardiovascular function during rest and exercise in patients with sickle-cell anemia and coexisting alpha thalassemia-2

Cardiac function was measured at rest and during exercise in 9 patients with sickle-cell anemia (SS) and coexisting homozygous alpha thalassemia-2 (alpha thal-2). Results were compared with 18 sickle cell patients with normal alpha globin genes, who were matched to the study group by age, gender, and size, and to published normal values. SS alpha thal-2 patients were less anemic: 9.9 +/- 1.0 vs 8.2 +/- 1.2 gm/dl for SS alone (P<.05). Left ventricular dimensions were normal in SS alpha thal-2 (4.9 +/- 0.7 cm), but increased in SS (5.4 +/- 0.7, cm P=.05) (normal range, 3.7-5.6 cm). Left ventricular wall thickness was, however, dramatically increased in the SS alpha thal-2 patients (free wall, 1.8 +/- 0.6 cm; septum, 1.6 +/- 0.4 cm), though SS controls had normal wall thickness (free wall, 1.0 +/- 0.2 cm; septum, 1.0 +/- 0.2 cm, P<.001) (normal range, 0.6-1.1 cm). At rest, Doppler indices of systolic function were not significantly different between sickle groups and normal values. SS alpha thal-2 patients did have abnormal diastolic filling at rest, as evidenced by a reduced ratio of early/late diastolic filling, 1.4 +/- 0.3 vs. 2.0 +/- 0.5 for SS controls (P<.01), and 1.8 +/- 0.4 for normals. An analysis of covariance suggested that this abnormality persisted after taking into account the previously demonstrated hypertrophy. During exercise, SS alpha thal-2 patients had higher heart rates and blood pressures than SS controls in spite of performing the same or less work. This resulted in a higher double product (an estimate of oxygen consumption) in SS alpha thal-2 patients (37,470 +/- 2,310 mm Hg-BPM) than in SS controls (33,310 +/- 1,490 mm Hg-BPM, P<.01). Work capacity, peak heart rate, and blood pressure were all abnormally decreased in both sickle-cell groups when compared to normal. Cardiac abnormalities noted at rest and during exercise in SS alpha thal-2 patients suggest a role of microvascular occlusion and a protective effect of decreased hemoglobin.

Anemia

OBJECTIVES

To provide an overview of the disorders that cause anemia and to review clinical and laboratory assessment and medical and nursing management of the anemic patient.

DATA SOURCES

Published articles and book chapters that pertain to red blood cell physiology and the major causes and types of anemia.

CONCLUSIONS

Advances in molecular and genetic aspects of anemia are leading to new developments in the diagnosis and management of all types of anemia. Symptomatic relief to maintain quality of life is essential for all anemic patients.

IMPLICATIONS FOR NURSING PRACTICE

Nurses can play a major role in the supportive care of patients with anemia through interventions related to pharmacological therapy, blood transfusions, nutritional counseling, and symptom management.

DNA diagnosis for the detection of sickle hemoglobinopathies

At this time, the sole generally accepted use for DNA diagnosis in the hemoglobinopathies is for the prenatal detection of disease, which can be identified by these means early in the first trimester of pregnancy. By ascertaining genotype rather than phenotype, the confusion that results from diagnostic errors should be diminished. DNA diagnostics are the future of all genetic disease detection and this future will soon be upon us.

Clinical, hematological, and molecular features in Sicilians with Hb S-beta-thalassemia

The clinical, hematological, and molecular features of 81 patients with Hb S-beta-thalassemia and relatives from 76 unrelated families are reported. We analyzed the beta-thalassemia mutations and the beta S haplotypes in all patients and detected 6 different beta-thalassemia alleles: codon 39 (C-->T) (39 cases), IVS-I-1 (G-->A) (12 cases), IVS-II-1 (G-->A) (4 cases), IVS-I-6 (T-->C) (6 cases), IVS-I-110 (G-->A) (14 cases), and IVS-II-745 (G-->C) (6 cases). Eighty patients had haplotype #19 or the Benin type and one had haplotype #17 or the Cameroon type. The type of beta-thalassemia allele had the greatest influence on the phenotypic expression; this was observed for patients with Hb S-beta-thalassemia and for simple beta-thalassemia heterozygotes. The mild IVS-I-6 (T-->C) mutation produced borderline abnormal erythrocytic indices and Hb A2 levels in heterozygotes. Overall, there was a milder expression in beta(S) beta(+) patients (only 7.7% presented severe disease) than in those with the beta(S)beta(0) condition (22.6% had the severe form of the disease).