title: [Usefulness of HLA-B27 in the diagnosis of ankylosing spondylitis: positive and negative predictive value and the probability ratio of diseases].
abstract: The authors discuss the usefulness of the HLA-B27 test in the diagnosis of ankylosing spondylitis (AS). Sensitivity, Specificity, Predictive Value of a Negative Test, Predictive Value of a Positive Test, and Likelihood Ratio are defined and illustrated through the example involving HLA-B27 and AS. The HLA-B27 cannot be used as a screening test for the diagnosis of AS when evaluating an asymptomatic population, however the test is most useful in assisting the diagnosis of AS when used by physicians who understand the principles of probability.
authors.affiliation: Escola Paulista de Medicina, Disciplina de Reumatologia, Rua Botucatu, São Paulo.
authors.forename: M B
authors.initials: MB
authors.lastname: Ferraz
authors.forename: R
authors.initials: R
authors.lastname: Sesso
authors.forename: E
authors.initials: E
authors.lastname: Atra
mesh_terms: D015796:HLA-B27 Antigen / Q000032:analysis*; D006801:Humans; D011237:Predictive Value of Tests; D015995:Prevalence; D011336:Probability; D012680:Sensitivity and Specificity; D013167:Spondylitis, Ankylosing / Q000175:diagnosis*
chemical_list: D015796:HLA-B27 Antigen
vernacular_title: Utilidade do HLA-B27 no diagnóstico da espondilite anquilosante: valor preditivo positivo e negativo e razão de probabilidade de doença.