A recently described β chain variant, Hb Valletta (or α2β287PRO; Felice .at aJ., BLOOD, 74, 7, suppl. 1, 141a, 1989) has been observed among 1.8% of the Maltese population among whom β+ & βo thal occur with a combined heterozygous incidence of 2.4 %. This provides an opportunity to quantify objectively, through the proportion of Hb A or of β(A) chains in double heterozygotes, the degree of functional deficit due to the β+ thal mutations which prevail in this area.peer-reviewe
