Thalassemia

Thalassemia, common in Thailand, varies from mild to severe anemia, resulting in work inefficiency, particularly during exertion. Therefore, it is important for military cadets to be screened. The objective of this study was to screen for thalassemia and hemoglobinopathies among Royal Thai Army medical cadets. We tested 358 third-year Royal Thai Army medical cadets for complete blood count, red blood cell indices, hemoglobin (Hb) typing, inclusion bodies, and Hb A^sub 2^, and Hb E. DNA analysis confirmed [alpha]-thalassemia^sub 1^ trait detection. The Hb E trait was the most frequent, respectively, in men and women, at 12.61% and 12%, followed by the [alpha]-thalassemia^sub 1^ trait, at 3.3% and 4% and the [beta]-trait, at 1.5% and 0%. Two cases of homozygous Hb E were found only in men. Interestingly, a mild form of [beta]-thalassemia/Hb E was found in one male RTA medical cadet. These findings suggest that consistent thalassemia screening should be considered.

Introduction

Thalassemia is one of the most common autosomal recessive diseases in Thailand and Southeast Asian countries.1-3 Presently, more than 10 million Thais carry the thalassemia gene for the disease and trait; approximately 600,000 have thalassemia disease. The most common thalassemia diseases are hemoglobin (Hb) Bart's hydrop fetalis, Hb H disease, homozygous [beta]-thalassemia, and [beta]-thalassemia/Hb E ([beta]/E) disease. The prevalence rates of thalassemia diseases are [alpha]-thalassemia, 20% to 30%; [beta]-thalassemia, 3% to 9%; Hb E, 13%; and Hb Constant Spring, 1% to 8%.3 The severity of the disease varies from mild to severe anemia. Thus, these patients require repeated red blood cell (RBC) transfusions to maintain their activities.4 Therefore, in Thailand, the Ministry of Public Health has set up a 10-year program of prevention and control of thalassemia, not only to support the patients' quality of life, but also to prevent thalassemia by reducing the number of new cases. This program includes population screening for heterozygotes, genetic counseling, and fetal diagnosis with selective abortion of affected pregnancies. Different levels of screening tests for thalassemia have been introduced such as the red cell one-tube osmotic fragility test (OF) combined with the dichlorophenol-indolphenol (DCIP) precipitation test, and complete blood count (CBC) and RBC indices, including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and RBC distribution width (RDW).5-9 However, additional confirmatory tests such as Hb typing and determination of Hb A^sub 2^ and Hb E and DNA analysis are needed.10 Previous studies in 552 Royal Thai Army (RTA) recruits showed that 26 recruits were anemic, of which 21 were due to the thalassemia gene, which may lower efficiency.11 Because there has been no report on the prevalence of thalassemia among RTA medical cadets, this study aimed to screen this group for thalassemia and hemoglobinopathies.

Methods

We tested EDTA blood samples from 358 third-year RTA medical cadets who attended the Clinical Pathology Course, Department of Pathology, Phramongkutklao College of Medicine, Bangkok, Thailand from September 1996 to October 2002, comprising 333 men and 25 women. On each blood sample, we performed CBC, RBC indices, Hb typing, inclusion bodies, and we tested for Hb A^sub 2^ and Hb E. Additionally, we also performed DNA analysis of the [alpha]-thalassemia^sub 1^ gene in samples testing positive for inclusion bodies.

CBC and RBC indices were measured by automatic cell analyzer (Coulter Onyx, Hialeah, Florida). From September 1996 to September 2000, Hb typing was conducted by starch gel electrophoresis12 and percentage determination of Hb A^sub 2^ and Hb E was conducted by microcolumn chromatography.13 Since September 2000, both tests were done by automated low-performance liquid chromatography (Hb GOLD, Drew, U.K.).14 To screen for the [alpha]-thalassemia, trait, the inclusion bodies test was used.15 [alpha]-Thalassemia^sub 1^ gene detection was performed by polymerase chain reaction as described.16

Results

During the study period, 358 subjects were tested for CBC, RBC indices, Hb typing, and inclusion bodies, and Hb A^sub 2^ and Hb E were determined. In male subjects, we found 272 (81.68%) of 333 were normal, 42 (12.61%) had the Hb E trait, 11 (3.3%) had the [alpha]-thalassemia, trait, 5 (1.5%) had the [beta]-thalassemia trait, 2 (0.6%) had homozygous Hb E, and 1 (0.3%) had [beta]/E disease. Regarding female subjects, we found 21 (84%) of 25 were normal, 3 (12%) had the Hb E trait, and 1 (4%) had the [alpha]-thalassemia^sub 1^ trait, as shown in Table I.

In 272 normal male subjects, the mean values of Hb and hematocrit (Hct) were 15.3 ± 1.1 g/dL and 45.2 ± 3.2%, respectively. The mean values of MCV, MCH, and MCHC were 88.4 ± 3.9 fl, 30 ± 1.5 pg/dL, and 33.9 ± 1.3 g/dL, respectively. The percentages of RDW and Hb A^sub 2^ were 13.2% ± 0.7% and 2.8 ± 0.4%, respectively. Moreover, all subjects were negative for inclusion bodies.

In Hb E trait subjects, the mean values of Hb and Hct were 14.5 ± 0.9 g/dL and 43.4 ± 3%, respectively. The mean values of MCV, MCH, and MCHC were 78.9 ± 3.5 fl, 26.3 ± 1.6 pg/dL, and 33.1 ± 1.7 g/dL, respectively. The percentages of RDW and Hb E were 14.2 ± 0.9% and 29.1 ± 3%, respectively. All were negative for inclusion bodies.

In [alpha]-thalassemia^sub 1^ trait subjects, the mean values of Hb and Hct were 13.9 ± 0.9 g/dL and 43.8 ± 2.3%, respectively. The mean values of MCV, MCH, and MCHC were 69.9 ± 2.1 fl, 22.2 ± 0.6 pg/dL, and 31.8 ± 0.9 g/dL, respectively. The percentages of RDW and Hb A^sub 2^ were 15.9 ± 1.2% and 2.2 ± 0.6%, respectively. All subjects were positive for inclusion bodies and confirmatory tests (DNA analysis of the [alpha]-thalassemia^sub 1^ gene).

In [beta]-thalassemia trait subjects, the mean values of Hb and Hct were 13.3 ± 1.0 g/dL and 41.6 ± 2.2%, respectively. The mean values of MCV, MCH, and MCHC were 61.2 ± 1.4 fl, 19.5 ± 0.7 pg/dL, and 31.9 ± 0.9 g/dL, respectively. The percentages of RDW and Hb A^sub 2^ were 16.2 ± 0.6% and 5.2 ± 0.6%, respectively. All were negative for inclusion bodies. The laboratory results for homozygous Hb E and [beta]/E disease subjects are shown in Table II.

In 21 normal female subjects, the mean values of Hb and Hct were 12.9 ± 1.4 g/dL and 38.2 ± 4.2%, respectively. The mean values of MCV, MCH, and MCHC were 88.9 ± 4.1 fl, 30.1 ± 1.6 pg/dL, and 33.9 ±1.3 g/dL, respectively. The percentages of RDW and Hb A^sub 2^ were 13.4 ± 0.6% and 2.6 ± 0.4%, respectively. All were negative for inclusion bodies. Hb E trait and [alpha]-thalassemia^sub 1^ trait subjects results are shown in Table III.

Discussion

The present study shows the prevalence of thalassemia among RTA medical cadets. The most common type in both genders is Hb E trait, which is similar to previous findings in Thailand and other Southeast Asian countries.1-3 In general, healthy individuals who carry the Hb E trait cannot be distinguished by routine CBC; only MCV is slightly decreased. Previous studies introduced the DCIP precipitation test to screen for Hb E;6 nevertheless, we performed Hb typing to determine different types of abnormal Hb. Additionally, homozygous Hb E was detected in two male RTA medical cadets. We found not only an abnormality of Hb E, but also slightly low values of Hb, Hct, and RBC indices. Confirmation of the [alpha]-thalassemia^sub 1^ gene by DNA analysis was carried out in all subjects who were positive for inclusion bodies and showed a decrease in MCV. Unfortunately, the determination of the [alpha]-thalassemia^sub 2^ gene was not included; this may reflect the low prevalence of the [alpha]-thalassemia gene in this study. In addition, two cases of normal female subjects were found to have slightly decreased Hct and Hb, but MCV and MCH were normal, which may be due to inadequacy of iron or other anemic causes.17

With regard to the [beta]-thalassemia trait group, we found abnormal RBC indices with increased percentages of the Hb A^sub 2^ level. One study showed that the OF test and/or abnormal electrophoretic pattern can be used as a screening test for thalassemia in Hellenic Army recruits.5 A combination of the OF test and the DCIP precipitation test was beneficial in screening for the Hb disorder in pregnant Thai women.6 The OF test showed a high sensitivity for [alpha]- and [beta]-thalassemia screening, whereas the DCIP precipitation test was effective for the detection of Hb E disorders. Both tests are useful for mass screening because of their simplicity and speed. However, further tests are needed to ensure more accurate results.7,8,18

Furthermore, one case of [beta]/E disease was detected in a male RTA medical cadet. Although he had a healthy appearance, the CBC and RBC indices and Hb typing were abnormal. Even though the severity of his disease was mild, long-term difficulties in his study and military activities are expected.

Conclusion

These findings suggest that a suitable routine screening program for the thalassemia gene is required to recruit high-quality military candidates, especially in countries with a high prevalence of thalassemia.

References

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Guarantor: COL Oytip Nathalang, MC RTA

Contributors: COL Oytip Nathalang, MC RTA*; LT COL Pasra Arnutti, MC RTA*; COL Kamolthip Nillakupt, MC RTA[dagger]

* Department of Pathology, Phramongkutklao College of Medicine, 315 Rajavithi Road, Rachathewi, Bangkok 10400, Thailand.

[dagger] Department of Biochemistry, Phramongkutklao College of Medicine, 315 Rajavithi Road, Rachathewi, Bangkok 10400, Thailand.

This manuscript was received for review in March 2003 and was accepted for publication in June 2003.

Reprint & Copyright © by Association of Military Surgeons of U.S., 2004.

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