Blood, 15 June 2001, Vol. 97, No. 12, pp. 3999-4000
CORRESPONDENCE
To the editor:
Alloimmunization in Hong Kong southern Chinese
transfusion-dependent thalassemia patients
We read with interest Singer et al's report showing an
increased alloimmunization and erythrocyte autoimmunization in a group of 64 transfusion-dependent thalassemia patients of predominantly Asian
descent.1 These patients have been receiving
phenotypically different red blood cells from predominantly white
donors. We would like to share our experience in Hong Kong.
We have been treating a comparable number (68) of thalassemic
patients (mean age, 18 years; range, 4-27 years) on regular transfusion. In this group 67 are of southern Chinese origin, and our
blood donors are predominantly of the same ethnic origin. Of
the 68 patients, 65 had 
thalassemia major and 3 had HbE/ thalassemia heterozygocity syndrome. Using standard blood bank methods,
serum was analyzed prior to each transfusion for detection of new
antibodies to red blood cell antigens. We employed the same logarithm
as Singer's for a further confirmation assay once antibody screening
became positive. We always issue fully phenotypically matched blood to
those who have an alloantibody in order to prevent further
alloimmunization. We rarely need to transfuse K antigen-matched blood, contrary to what Singer et al had
suggested.1 We had observed a total of 9 alloantibodies in
5 patients (of 68) with 7.4% detection rate (unpublished data, April
2001) as compared with 22% (14 of 64) as reported by Singer et
al. Only 1 of our 68 patients had an autoantibody, compared with 6 of
64 in Singer et al's report.1 All our patients with
alloantibodies have more than 15 years of regular blood transfusion
(range, 15-26 years). Among the 9 alloantibodies detected in our
patients (3 Anti-E; 3 Anti-Mi; 1 Anti-HLA; 1 Anti-BG, 1 Anti-BW22),
only Anti-E has been reported to be clinically significant, causing a
hemolytic transfusion reaction. Singer et al also noticed a relatively
high rate of Anti-E (21%), and they could not attribute it to a
recipient-donor antigenic discrepancy. Anti-K was not encountered in
our patients, unlike the 6 of 19 (31%) anti-K alloantibodies in Singer
et al's group. No single alloantibody for c, S, and Fyb was found in
our patients. All of our patients' alloantibodies were developed
before we introduced universal leukodepletion for thalassemic patients. This observation is in line with Singer et al's observation that a
significantly lower alloantibody rate had resulted from the introduction of leukodepletion.1 Twelve our patients
underwent splenectomy, but only 1 of those 12 had alloantibodies and
she developed the antibody before splenectomy. And only 1 of the 12 had
autoantibodies after splenectomy. Our experience did not substantiate Singer et al's observation that patients who underwent splenectomy had
a higher alloimmunization rate.1
Previous data on a presumed homogenous population in Greece and Italy
also showed an overall low rate (5% to 10%) of
alloimmunization.2-3 The difference between our experience
of lower rate of alloimmunization (7.4%) and Singer et al's higher
rate (22%) can be explained by our access to phenotypically matched
donors in Hong Kong. We agree with Singer et al's recommendation that
the recruitment of Asian blood donors in North America, just like the
recruitment of black donors for sickle cell disease patients, can
increase the availability of compatible blood for thalassemia
patients, who have a lifelong need for transfusions.
Hok-Kung Ho, Shau-Yin Ha, Chun-Kit Lam, Godfrey C. F. Chan, Tsz-Leung Lee, Alan K. S. Chiang, and Yu-Lung Lau
Correspondence: Hok-Kung Ho, Division of Hematology, Oncology,
and Immunology Department of Paediatrics, Queen Mary Hospital, The
University of Hong Kong, Hong Kong SAR, China
References
1.
Singer ST, Wu V, Mignacca R, Kuypers FA, Morel P, Vichinsky EP.
Alloimmunization and erythrocyte autoimmunization in transfusion-dependent thalassemia patients of predominantly Asian descent.
Blood.
2000;96:3369-3373[Abstract/Free Full Text].
2.
Sirchia G, Zanella A, Parravicini A, Morelati F, Rebulla P.
Red cell alloantibodies in thalassaemia major: results of an Italian cooperative study.
Transfusion.
1985;25:110-112[CrossRef][Medline]
[Order article via Infotrieve].
3.
Economidou J, Constantoulakis M, Augoustaki O, Adinolfi M.
Frequency of antibodies to various antigenic determinants in polytransfused patients with homozygous thalassemia in Greece.
Vox Sang.
1971;20:252-258[Medline]
[Order article via Infotrieve].
Response:
Differences in alloantibody types detected in transfused Asian
thalassemia patients
Ho et al add important data for better understanding the causes
for alloimmunization in Asian thalassemia patients undergoing transfusion. Their data assists in delineating these causes among homogenous and less homogenous donor-recipient populations. The differences in the type of antibodies detected in our and Ho et al's
study may also be largely due to the red blood cell phenotypic discrepancy.
We agree with Ho et al that the effect of absence of spleen on allo-
and autoantibody development is not completely clear. Our data
suggested a higher frequency among patients in which the spleen was
removed but has not reached statistical significance. Larger studies,
in patients from various ethnic backgrounds, are needed to address this issue.
Sylvia T. Singer
Correspondence: Hematology/Oncology, Children's
Hospital Oakland, 747 52nd St, Oakland, CA
94609
