title: Estimating the allele frequency of autosomal recessive disorders through mutational records and consanguinity: the Homozygosity Index (HI).
abstract: In principle mutational records make it possible to estimate frequencies of disease alleles (q) for autosomal recessive disorders using a novel approach based on the calculation of the Homozygosity Index (HI), i.e., the proportion of homozygous patients, which is complementary to the proportion of compound heterozygous patients P(CH). In other words, the rarer the disorder, the higher will be the HI and the lower will be the P(CH). To test this hypothesis we used mutational records of individuals affected with Familial Mediterranean Fever (FMF) and Phenylketonuria (PKU), born to either consanguineous or apparently unrelated parents from six population samples of the Mediterranean region. Despite the unavailability of precise values of the inbreeding coefficient for the general population, which are needed in the case of apparently unrelated parents, our estimates of q are very similar to those of previous descriptive epidemiological studies. Finally, we inferred from simulation studies that the minimum sample size needed to use this approach is 25 patients either with unrelated or first cousin parents. These results show that the HI can be used to produce a ranking order of allele frequencies of autosomal recessive disorders, especially in populations with high rates of consanguineous marriages.
authors.affiliation: Unità Operativa di Genetica Medica, Dipartimento di Scienze Ginecologiche, Ostetriche e Pediatriche, Policlinico Sant'Orsola Malpighi, Università di Bologna, Bologna, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gialluisi
authors.forename: Tommaso
authors.initials: T
authors.lastname: Pippucci
authors.forename: Yair
authors.initials: Y
authors.lastname: Anikster
authors.forename: Ugur
authors.initials: U
authors.lastname: Ozbek
authors.forename: Myrna
authors.initials: M
authors.lastname: Medlej-Hashim
authors.forename: Andre
authors.initials: A
authors.lastname: Mégarbané
authors.forename: Giovanni
authors.initials: G
authors.lastname: Romeo
mesh_terms: D003241:Consanguinity; D010505:Familial Mediterranean Fever / Q000235:genetics; D005240:Feasibility Studies; D005787:Gene Frequency; D005808:Genes, Recessive; D030342:Genetic Diseases, Inborn / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D008957:Models, Genetic; D009154:Mutation; D010661:Phenylketonurias / Q000235:genetics