PHENOTYPES OF GLUCOSE-6-PHOSPHATE-DEHYDROGENASE IN DIFFERENT REGIONS OF SAUDI-ARABIA - A COMPARATIVE-ASSESSMENT

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is the most freq uently encountered enzymopathy in most populations of the world. Due t o the clinical abnormalities associated with G-6-PD deficiency signifi cant attention has been directed to the study of G-6-PD phenotypes par ticularly those that cause hemolytic anemia. Materials and methods: Th is study was conducted in different regions of Saudi Arabia on 9130 Sa udis (males = 5130; females = 4,000). Blood samples were drawn by vene punture and centrifuged. The red cells were carefully removed and the hemolysate was used for the estimation of G-6-PD activity by spectroph otometric methods and for phenotyping of G-6-PD by electrophoresis on cellulose acetate plates at pH 5.6. The G-6-PD variants were identifie d as separate bands with different electrophoretic mobility and differ ent activity against the normal substrate glucose-6-phosphate. Results : The normal G-6-PD was G-6-PD-B+ in all areas of Saudi Arabia. The G- 6-PD variants identified included G-B-PD-A(+), G-6-PD-A(-), G-6-PD-Med , a variant with the same mobility as G-6-PD-Med but activity between 20-60% (G-6-PD-Med-like) and another variant G-6-PD with mobility les s than G-6-PD-B+ which also needs to be characterised. In the overall population the frequency of severe G-6-PD deficiency due to G-6-PD-Med was 0.1041 in the males and 0.061 in the females. When separated on t he basis of provinces, the highest frequency of G-6-PD-Med was in the eastern province and the lowest in the north-western males and central females. Significant differences were seen in the frequency of all th e variants in the different areas within each region. However, in all areas G-6-PD-Med was the most frequent variant causing severe G-6-PD d eficiency. Discussion: G-6-PD deficiency is a common problem in some p arts of Saudi Arabia particularly in the eastern and south-western pro vinces. The most frequent variant with normal activity is G-6-PD-A(+) while the most common variant causing severe G-6-PD deficiency is G-6- PD-Med. Since G-6-PD-Med is associated with several clinical abnormali ties there is a need for carefully designed screening programs in area s with a high frequency cf deficiency and the deficient individuals ne ed to carry a card listing drugs, food etc. to be avoided, to prevent hemolytic anemia due to G-6-PD deficiency.