Statistical approaches for the detection of heterozygotes for biotinidase deficiency
ABSTRACT We applied and evaluated 3 statistical approaches for the detection of heterozygotes for biotinidase deficiency in a randomly selected population of French adults. The first method, which used a cutoff value to dichotomize the population, lacked sensitivity. The second approach calculated the probability of heterozygosity for a given enzyme activity through the application of Bayes theorem to the normal density functions of the enzyme distributions of the obligate heterozygote and the test populations. A priori values of the means and standard deviations (SDs) of the genotypic distributions were used. This method was sufficiently sensitive for both population screening and genetic counseling, but requires prior knowledge of the frequency of the deficient gene (q). The third approach was similar to the second, however, maximum likelihood estimates of the means and SDs of the genotypic distributions were calculated and used to determine the probability of heterozygosity for a given enzyme activity. This method was as sensitive as the second method and is appropriate for screening populations for which there is little prior information about the gene frequency and the genotypic distributions. This method can also be used to estimate the gene frequency of the disorder within a given ethnic or racial population. Using this method, we estimated the frequency of heterozygotes (2pq) in the French population to be 0.012, which was similar to that estimated from the results of neonatal screening for biotinidase deficiency. These methods can be used to detect heterozygotes and to estimate the gene frequency of other inherited enzyme deficiencies.
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ABSTRACT: Biotinidase recycles the vitamin biotin. Biotinidase deficiency is an autosomal recessively inherited neurocutaneous disorder. The symptoms of the disorder can be successfully treated or prevented by administering pharmacological doses of biotin. The biotinidase gene (BTD) has been cloned and sequenced; its genomic organization has been determined and more than 150 mutations have been identified. The disorder meets the major criteria for newborn screening and is being universally adopted in the United States and in many countries around the world. Newborn screening will limit our understanding about the natural history of the disorder. Regardless, the disorder is an ideal example of an inherited metabolic disorder that if untreated can result in major disabilities, but if identified early can be readily treated by the oral administration of a vitamin.Genetics in medicine: official journal of the American College of Medical Genetics 01/2012; 14(6):565-75. DOI:10.1038/gim.2011.6 · 6.44 Impact Factor
Journal of Pediatrics 01/1990; 116(1):78-83. DOI:10.1016/S0022-3476(05)81649-X · 3.74 Impact Factor
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ABSTRACT: A 3 month old male child was brought to the hospital with complaints of skin rashes, developmental delay, seizures, seborrheic dermatitis, alopecia and mild, acidosis. The child was subjected to a simple metabolic screening protocol. The result of the screening and the clinical symptoms provided an index pointing towards biotinidase deficiency., a rare autosomal recessive, inherited metabolic disorder. The enzyme was then assayed by using n-biotinylp-aminobenzoate as substrate and the diagnosis confirmed. A follow-up of the case indicated the efficacy, of biotin supplementation in biotinidase deficiency.Indian Journal of Clinical Biochemistry 07/2003; 18(2):23-6. DOI:10.1007/BF02867363