[Diagnostic yield in studies of autism. The contribution made by neuroimaging, metabolic tests and genetic studies].

We reviewed the literature on the diagnostic yield of the different medical tests carried out on autistic patients in order to determine the aetiology of the process.Although it is generally said that a causation of the process can be determined in 10 30% of cases, the actual diagnostic yield of autism when a routine diagnosis is applied is between 2 and 7%. The diagnostic yield of radiology, metabolic studies and genetic studies was analysed. Genetic tests are the ones that offer the highest efficiency, and carrying out a karyotype and molecular study of fragile X chromosome syndrome is indicated in all patients with mental retardation associated to autism. The next most efficient are metabolic studies, which become particularly important mainly in populations where no screening has previously been conducted for metabolic disorders.Despite their being capable of showing up a large number of disorders, neuroimaging studies are unspecific and the diagnostic yield of radiological studies is very low when they are conducted on a routine basis.