Haemoglobin S and sickling in Khartoum province

48 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE.

Vol. 60. No.

1. 1966.

COMMUNICATIONS HAEMOGLOBIN S AND SICKLING IN KHARTOUM PROVINCE BY

F. VELLA*

Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada (Formerly Reader in Biochemical Genetics,Department of Biochemistry, Universityof Khartoum) It is commonly believed that sickling is a rare occurrence in the Sudan. TROWELL (1960) summed up the position as follows: "The sickling trait is found all over tropical and subtropical Africa, but is so rare as to be almost absent in the northern and southern parts of the continent. There is practically none in the Sudan and countries bordering the Mediterranean." Extensive sickle-cell surveys in the Sudan are few and have so far been reported only among peoples inhabiting regions to the south and west of Khartoum. The first such survey was made by FoYet al. (1954) on 2000 subjects distributed among 26 tribes and sub-tribes of the southern provinces. This was quickly followed by the search by ROBERTS and LF.rIMANN (1955) for sickling among some 740 Nilotics from Upper Nile Province. More recently, YOUSIF(1962) tested 1250 subjects in Bahr el Ghazal province, and VELLA (1964) examined 2400 subjects in and around Fasher in Darfur Province in the western part of the country. Since August 1960, falter-paper electrophoretic studies have been made as a routine on the haemoglobin of blood obtained from patients attending Khartoum General Hospital over several months in each year. A report on the first 1400 samples tested has already been made (VFLLA, 1960). A frequency for the sickle-cell trait of 2.4% was found in 8,000 blood samples in this hospital population. Sickling surveys of 2450 hospital out-patients in Omdurman and Khartoum North showed a frequency of 1.6% . It is the purpose of this communication to summarize the results of these investigations. Material Khartoum province (total population 505,000) comprises the 3 large towns of Khartoum (population 93,000), Khartoum North (38,000) and Omdurman (114,000), situated at the confluence of the Blue and White Niles, and a number of villages within easy reach of these towns. The population is composed mainly of "Arab" ("Northern" Sudanese) stock, served by a general hospital in each of these three towns. The subjects *I am grateful to the following without whose help these studies could not have been made: Dr. Mahmoud Abdel Rahman Ziada (Director, Khartoum General Hospital Blood Bank), Dr. Mamoun Yousif Hamid (Dept. of Public Health, University of Khartonm), the Senior Medical Officers at Omdurman and Khartoum North General Hospitals, and the medical students who helped in carrying out the sickling tests.

F. VELLA

49

examined in these investigations are considered representative of the population of this province. (The popu!ation figures are taken from The Sudan Almanac, 1960.) In all, 8500 blood samples were examined by filter-paper electrophoresis between August 1960 and February 1965. Of these, 8600 had been submitted to several pathological laboratories in Khartoum for a wide variety of biochemical, haematological and serological investigations, and had originated from in- and out-patients of both sexes and of all ages attending Khartoum General Hospital. Precautions were taken to avoid including several blood samples from the same person in these studies. The samples were obtained as follows: August 1960-February 1961 2230 samples. November 1962-March 1963 806 samples. August 1963-March 1964 2564 samples. August 1964-February 1965 2400 samples. It was not possible to obtain information on the tribal affiliations of the patients studied, but not more than 5% were estimated to have come from people belonging to Negro or Nilotic tribes found in the southern parts of the country. The other 500 samples were obtained from blood donors attending the Khartoum General Hospital Blood Bank (Director: Dr. Mahmoud Abdel Rahrnan Ziada) between August 1963 and March 1964. All these donors were male, adult Sudanese "Arabs." During November 1963, sickling tests were made on 1386 consecutive out-patients attending Omdurman General Hospital; of these 288 were children under the age of 10 years. During November 1964, 1060 consecutive out-patients were tested at Khartoum North General Hospital; of these 166 were children under the age of 10 years. At this time also 190 male school children at E1 Hag Yusif Village school, 5 miles east of Khartoum North, were tested. These children belonged mainly to the Batahin tribe. In these surveys an indication of the tribal affiliations of the subjects was obtained by questioning. Methods

Electrophoresis was carried out on filter-paper at pH 8.8, with barbiturate-barbituric acid buffer, and "hanging strip" electrophoresis tanks. Runs were made at about 5°C. All haemoglobin solutions which were found to contain an abnormal fraction were tested with a modification of Itano's solubility test. Only those samples which contained a reduced haemoglobin of subnormal solubility in this test were considered to contain haemoglobin S. Several of these samples were confirmed as containing haemoglobin S, when they were examined by Dr. H. Lehmarm of the Medical Research Council's Abnormal Haemoglobins Research Unit, University of Cambridge, England. The sickling test was that described by DALA~D and CASTLE(1948), with fresh 2% sodium metabisulphite solution and microscopic examination after 20 minutes. This test, in our hands, gives positive results only when a haemoglobin solution from the sample of blood contains an abnormal fraction identical with haemoglobin S on electrophoresis, and gives an abnormal Itano's solubility test. These methods have already been described (VF.LLA,1963). Results

The results of electrophoretic analysis of the 8500 specimem in this study are summarized in Table I. 226 samples contained haemoglobin S (2.66% of the total), of which 202 contained haemoglobin A + S (2.38%) and 24 contained haemoglobins S + F (0.28%). All these 24 samples were from children aged 9 months to 8 years,

50

HAEMOGLOBINS AND SICKLINGIN KHARTOUMPROVINCE TABLEI.

Frequency of haemoglobin S in Sudanese subjects in the present study. Haemoglobin A + S Total studied

Source Khartoum hospital patients

8000

Total i

188

,

I

Haemoglobin S + F

%

Total

%

2.35

24

0"30

2.80

nil

nil

i

Blood donors

500

14

8500

202

I

!

I

2 "38

24

0.28

and contained haemoglobin F (i.e., al~li-resistant haemoglobin as measured by Singer's "one minute" denaturation test (VELLA, 1963)) amounting to 5-53% of the total haemoglobin. The majority of these probably represented instances of sickle-cell anaemia, though a few were probably sickle-cellmthalassaemia. Testing of both parents was only possible in a few instances. The frequency of the haemoglobins A + S pattern in blood donors was 2.8%. The results of the sickle-cell surveys in Omdurman and Khartoum North are summarized in Table II. Sickling was present in 1.59 and 1.69% respectively of the

TABLE II.

Frequency of siclding in Omdurman and Khartoum North. Total studied

Sickling positive

%

Omdurman hospital

1382

22

1.59

Khartourn North hospital

1060

18

1.69

Source

E1 Hag Yusif school

190 2632

0.00 40

1.52

out-patients tested in these two hospitals. No instances of sickling were detected in the boys attending El Hag Yusif Village School. Combining the results of electrophoretic analysis and of the sickle-cell surveys, it is seen that out of a total of 11,132 persons tested, 266 (2.38°/0) had haemoglobin S (as haemoglobin A + S , or S + F ) or gave positive siclding tests. In Table III the frequencies of sickling found in this study are compared with those found in Fasher (V~Lr.A, 1964) in 10 tribal groups. Only in the case of the Gaali tribe does there appear to be a significant difference in siclding frequency (7-14% in Fasher, against 0.78% in Omdurman and 0.0°/0 in Khartoum North). In 52 samples (0-61%) an abnormal haemoglobin fraction which was not identical with haemoglobin S was found in association with haemoglobin A. These results are summarized in Table IV and are being prepared for publication separately.

F. VELLA

TABLE I I I .

51

Comparison of sickling in some tribal groups in Omdurman, Khartoum N o r t h and Fasher ! f

OMDURMAN

KHARTOUM NORTH

Tested

+

! 255

2 0"78

152

0 0"00

Dongolawi

122

2 1"64

50

Shalgi

104

1 0"96

75

TRIBE

Gaa5

Mahasi Nubawi Mugrabi Dinka

Ip I

! i [

Bideri Gamai Furawi

]l I'

Others Total

~o Tested

+

FASHER

%

Tested

THE THREE SURVEYS COMBINED

+

%

Tested

+

84

6

7"14

491

8 1.63

0 0.00

33

3

9"09

205

5 2.44

104

0 0"00

29

1

3"45

237

2 0"84

0 0"00

84

0 0.00

27

1

3"70

186

1 0.54

57

0 0.00

51

2 3.92

24

0

0"00

132

2 1.51

19

0 0-00

21

0 0.00

20

2 10.00

60

2 3.33

21

0 0.00

50

1 2.00

42

1

2"38

113

24

1 4'16

7

0 0'00

25

2

8.00

56

3 5.36

39

1 2'56

70

3

4"28

109

4 3-67

146

8

5"48

177 I

9 5.08

2

%

1-78

5"88

14

0 0"00

653 ~ 14 2 ' 1 4

527

15 2.84

1925 177

9"20! 3105 '206 6"63

1060

18 1.69

2425 204

8-41

17

1386

i

1

22

1"59

4871 244

5"01

P

Data for Fasher from VELLA (1963). TABLE IV.

Other abnormal haemoglobin fractions detected on electrophoresis.

Total number of samples analysed

8500

Fraction faster than haemoglobin A

3 (0"035%)

Fraction faster than haemoglobin S

35 (0.41%)

Fraction slower than haemoglobin S

14 (0.16%)

Discussion

These studies indicate that haemoglobin S is present in an appreciable n u m b e r o f the inhabitants o f K h a r t o u m province. Sickle-ceU anaemia is b y no means rare and deserves to be considered in all children attending any o f the hospitals in this province. I t is significant that only a small n u m b e r o f the 24 patients ( 0 . 2 8 % o f those analysed) with a sickle-ceU anaemia electrophoretic pattern were being examined specifically to confirm or exclude this diagnosis. I n many, the hereditary abnormality was submerged b y intercurrent disease though it was contributing noticeably to the clinical features o f the disease.

52

HAEMOGLOBIN S AND SICKLING I N KHARTOUM PROVINCE

The other abnormal haemoglobin variants, though of great anthropological interest, occurred only in the trait form and were not of any clinical interest. It is not unlikely that there exist in the three towns studied regional differences in the frequency of sickling, depending on the tribal affiliations of the population in various parts of the towns. There were no instances of sickling among the school children in a village 5 miles from Khartoum North. The out-patients attending the town hospital showed a frequency of 1.69~/o. This supports the finding of uneven frequencies in the three towns as shown in Tables I and II. The Sudan with its population of 12.5 million scattered over approximately a million square miles, with its numerous tribes and sub-tribes, with its geographical, tribal and historic relations with African neighbours in the south and west in whom the frequencies for sickling are known to be among the highest in Africa, deserves to be more adequately surveyed for the sickling trait than it has been so far. The studies reported can be considered as no more than pointers to the seriousness of this condition in the southern and the western regions. The present results, obtained among peoples who are normally classed as "Arabs" and therefore mistakenly assumed to be free of this "Negro" characteristic, indicate its broad distribution.

Summary Since August 1960, electrophoretic studies have been made on 8000 blood samples mainly from Sudanese "Arab" patients attending Khartoum General Hospital, and on 500 Sudanese blood donors. Haemoglobin S was found in 2.66% of all samples (as haemoglobin A + S in 2-38% and as S + F in 0.28~/o). Other abnormal haemoglobin variants were found in 0.6%. Sickling tests on 2632 persons in Omdurman and Khartoum North gave positive results in 1- 52%. The need is stressed for more sickling surveys in the Sudan, to determine more precisely the distribution of this hereditary abnormality. ADDENDUM Electrophoretic analysis of 600 other blood samples from Khartoum Hospital patients, examined in February and March, 1965 (after this paper was written) revealed the following patterns: haemoglobins A and S,16; S and F,1; A and faster than S,3; A and slower than S,3. REFERENCES FoY, H., KONDI, A., TIMMS, G. L., BRASS,W. & BUSHRA,F. (1954). Brit. med. J., 1, 284. DALAND, G. A. & CASTLE,W. B. (1948). 3:. Lab. clin. A/led., :i3, 1082. ROBERTS,R. D. & LEHMANN,H. (1955). Brit. med. ft., 1, 519. TROWELL, H. C. (1960). Non-Infective Disease in Africa. London: Edward Arnold, p. 405. VELLA, F. (1961). E. Afr. reed. y., 38, 350. (1963). Sudan med. 7-, 2, 77. (1964). Ibid., 3, 16. YOUSlF, A. A. (1962). El Hakeim (September), p. 30.