Red Cell Indices in Thalassemia Minor

HENRY G. SCHRIEVER, M.D.

Department of Pathology, John F, Kennedy Community Hospital, Edison, NJ 08817

ABSTRACT Red cell size and hemoglobin content, as measured by the Coulter Counter Model S, are consistently and rather uniformly decreased in thalassemia minor. Red cell count, hemoglobin and hematocrit are more variable and may even be normal. The finding of mean corpuscular volume (MCV) 53 to 71 p? and mean corpuscular hemoglobin (MCH) 17 to 25 pg should raise the suspicion of thalassemia minor. The MCV/RBC quotient is regularly under 13 in thalassemia minor and over 13 in non-thalessemic microcytosis except for some overlap in women. A presumptive diagnosis can then be made by the finding of target cells and basophilic stippling of red cells on the peripheral blood smear. Demonstration of elevated A2 hemoglobin level clinches the diagnosis. (RBC = red blood cells.)

Beta thalassemia minor is an hereditary making the diagnosis is outlined which can hypochromic microcytic anemia, probably be used for inexpensive mass screening for a mutation favored by selection over many the condition. Complete blood counts were generations in Mediterranean peoples to done on 93 patients with thalassemia minor provide protection against the malarial par on the Coulter Counter Model S.* Pe asite.2’6’10 While thalassemia minor is harm ripheral blood smears were stained with less enough, the homozygous state of the Wright-Giemsa and examined in the usual gene produces a severe anemia, thalas manner. Quantitative hemoglobin A2 levels semia major or Cooley’s anemia, which is were done by a modification of the poly usually fatal before adulthood.7 Most pa acrylamide gel electrophoresis method of tients with thalassemia minor are either Bierman and Zettner.1 not anemic or are only mildly anemic. Most The results of the automated blood are quite unaware of their condition. It is counts are shown in table I. All of the important to establish a correct diagnosis patients with thalassemia showed signifi cant basophilic stippling of red cells and to avoid unnecessary iron treatment and to target cells on smear, features which were counsel patients about the possibility of not at all prominent in cases of iron de thalassemia major in their offspring. ficiency anemia with red cells indices in This report presents the diagnostic blood the thalassémie range. All patients with findings in a series of thalassemia minor patients. A simple stepwise procedure for * Coulter Electronics, Hialeah, FL 33010. 3 4 0 SCH RIE VER

TA BL E I

Peripheral Blood in 93 Patients with Thalassem ia M inor M ean ± Standard Deviation

Red C e ll Hemoglobin Count H em atocrit MCV* MCH* MCHC^ N g p e r d l 1 0 6 p e r cmm P ercen t p3 p g P ercen t

M en 29 1 2 . 6 0 ± 1 . 3 6 5.98±0.48 37 .6±3,84 6 2 .8 + 3 .8 8 20.7±1.57 33.13±0.86

Women 45 11.59±1.08 5.38+0.53 34 .89±3.16 64.22+3.51 21.33±1.40 3 3 .1 8 + 0 .9 8

C h i l d r e n 19 11.29+1.15 5 .6 3 + 0 .4 7 33,84±3.26 59.68±3.30 19.7±1.10 33 ,26±1.07 r- i—! N o r m a l M 1 4 - 18 1 42 - 52 82 - 92 27 - 31 32 - 36

F 12 - 16 4.2 - 5.4 37 - 47 81 - 94 27 - 31 32 - 36

*Mean corpuscular volume tMean corpuscular hemoglobin 'VMean corpuscular hemoglobin concentration thalassemia minor showed elevation of he in men greater than in children (p < 0.05); moglobin A2 in the 4.2 to 8.9 percent range MCV in women greater than in children (normal up to 4.1 percent). The t-test11 (p < 0.01); and MCH in women greater showed the following differences to be than in children (p < 0.002). The other statistically significant: hemoglobin and differences were not statistically significant. hematocrit in men greater than those in Mean corpuscular hemoglobin concentra women (p < 0.01); RBC in men greater tion (MCHC), a value which is sometimes than in women (p < 0.002); mens hemo decreased in iron deficiency anemia, was globin and hematocrit greater than chil normal in all but five cases. The overall dren s (p < 0.002); RBC in men greater thalassemic range for MCV was 53 to 71 p? than in children (p < 0.05); MCV in men and for mean corpuscular hemoglobin greater than in children (p < 0.01); MCH MCH from 17.5 to 25.4 pg. England and Fraser3 recently developed T A B L E II a mathematical “discriminant function” Discrim inant Function (D F) in Thalassem ia (DF) to differentiate thalassemia minor Trait and N on-thalassem ic M icrocytosis D F = M C V - R B C - (5 X Hb) - 3.4 from iron deficiency:

DF = MCV-RBC-(5 X H b) - 3.4 DF-f- DF- (Range) (Range) MCV is expressed in /xz, RBC in millions per cmm and Hb in grams per dl. They Non-thalassemia 19 1 * (MCV under 80) (2.1-60.2) (-13) found the DF regularly negative in thalas semia minor and positive in iron deficiency. Thalassemia trait In table II is shown the DF in thalassemia Men 1 28 minor and non-thalassemic microcytosis. (2.2) (-0.7 -- 22.5) Mentzer5 proposed an even simpler for Women 17 28 mula to differentiate the two conditions: (2.6-8.6) (0.0 -- 12.8) MCV/RBC; he found this quotient to be Children 2 17 usually over 13 in iron deficiency. In table (1.2-2.0) (-0.1 -- 24.1) III is shown this value in thalassemia and non-thalassemic microcytosis. The MCV/ *Mean corpuscular volume RBC quotient worked for men and chil RED CELL INDICES IN THALASSEMIA MINOR 341 dren, but the thalassemic women ranged TABLE III higher than 13 (up to 15.3), overlapping M e a n C o r p u s c u l a r V o l u m e P e r R e d B lo o d with the range for non-thalassemic micro- C e l l s (MCV/RBC) in T h a l a s s e m ia a n d N o n -thalassemic M icrocytosis cytosis both in men and women. The high values for women are due partly to their MCV/RBCf MCV/RBCf significantly lower RBC and partly to their u n d er 13 o v e r 13 tendency toward higher MCV values. Co (R an ge o f (R an ge o f V a lu e s) V a lu e s) existing iron deficiency was not a factor in the one thalassemic woman with MCV/ N on-thalassemia 0 2 0 RBC of 15.3; her serum iron was normal. *(MCV under 80) (13.0-19.5) Screening for thalassemia minor could proceed as follows: Thalassemia trait

M e n 28 1 1. The MCV and MCH are measured, ( 0 . 6 - 1 2 . 7 ) ( 1 4 . 1 ) looking for values in the thalassemic W om en 3 4 1 1 range, and the MCV/RBC value is ( 9 . 4 - 1 3 . 0 ) (13.1-15.3) calculated. 2. Where indices and/or the MCV/RBC C h i l d r e n 1 9 0 ( 8 . 7 - 1 2 . 8 ) value are suspicious, the peripheral blood smear is examined for target *Mean corpuscular volume cells and basophilic stippling. In a tMean corpuscular volume per red blood cells routine laboratory situation critical technique. In rare cases of thalas review of the blood film may be nec semia minor, A2 hemoglobin may be essary. normal, and hemoglobin F elevated.4 3. Confirmation of the diagnosis is made by precise measurement of the A2 In studying families known to have thal hemoglobin fraction by a quantitative assemia, A2 hemoglobin determination on

F i g u r e 1 . Peripheral blood smear in beta thal assemia minor showing target cells and baso philic stippling. When red cell indices are in the thalassemic range, these findings may be enough for a presump tive diagnosis of thalas semia minor. (X 1,000) 3 4 2 SCHRIEVER each member is hardly necessary, the di 3. E n g l a n d , J. M. and Fraser, P.: Differentia agnosis being obvious from the cell indices tion of iron deficiency from thalassemia trait by routine blood count. Lancet 1:449-452, and blood film. Additional laboratory tests, 1973. such as iron and iron binding capacity, 4. M a r k s , P. A.: Thalassemia syndromes. New osmotic fragility, bone marrow examination Eng. J. Med. 275:1363-1369, 1966. and the usual hemoglobin electrophoresis 5. M e n t z e r , W. C.: Differentiation of iron de ficiency from thalassemia trait. Lancet 1:882, done for hemoglobinopathy, are super 1973. fluous in most cases. Alpha thalassemia 6. M o t u l s k y , A. G.: Current concepts of the trait is also prevalent in Mediterranean and genetics of the thalassemias. Cold Spring Har bor Symposium on Quantitative Biology 29: Oriental peoples8-10 and may be present 399-413, 1964. when the MCV/RBC value and the periph 7. N a t h a n , D. G.: Mild thalassemia—a guide to eral blood smear suggest thalassemia al therapy. New Eng. J. Med. 281:1363—1364, 1969. though hemoglobins A2 and F are normal.9 8. N a t h a n , D. G.: Thalassemia. New Eng. J. Erythrocyte morphology may be normal in Med. 286:586-594, 1972. alpha thalassemia trait, however.10 9. P e a r s o n , H. A., O’Brien, R. T., a n d M c I n t o s h , S.: Screening for thalassemia trait by electronic measurement of mean corpuscular R eferences volume. New Eng. J. Med. 288:351-354, 1973. 1. B i e r m a n , A. H. and Zettner, A.: A simple electrophoretic method for the quantitative 10. Rucknagle, D. L.: On the geographical dis determination of hemoglobin A2. Amer. J. tribution and ethnic origin of thalassemia. Clin. Path. 37:139-142, 1967. New Zea. Med. J. Hema. Suppl. 65:826-831, 2. C h e r n o f f , A.: The distribution of the thal 1966. assemia gene: a historical review. Blood 14: 11. Statistical Analysis. Olivetti Corporation of 897-912, 1959. America, New York, pp. 188-193, 1968.

Plan to attend the 25th Anniversary Meeting of the

ASSOCIATION OF CLINICAL SCIENTISTS

in Philadelphia, PA on November 8, 9 and 10, 1974

Applied Seminar on the

Laboratory Diagnosis of Skeletal, Muscular and

Nervous Disorders