title: What is the probability of a patient presenting a pleural effusion due to tuberculosis?
abstract: BACKGROUND
  In Rio de Janeiro, in almost half of the cases of pleural tuberculosis (PT) treatment begins without substantiation of diagnosis. We examined variables associated with this disease.
  
  
  METHODS
  We studied 215 consecutive patients; 104 had tuberculosis (TB) and 111 did not (NTB): 41 neoplasms, 29 transudates, 28 para-pneumonic and 13 other etiologies. Clinical and laboratory variables were assessed in a combined manner using likelihood ratios (LR) and Bayes' theorem to determine the probability of PT.
  
  
  RESULTS
  Among the variables examined, adenosine deaminase (ADA) levels, lymphocyte cell percentage, protein and age were the best indicators for the diagnosis of PT. Association of ADA with any of the other variables led to a LR+ higher than 10 and a LR- lower than 0.1, indicating the presence or absence of PT, with an individual probability of more than 90% or of less than 10% considering that there was a 50% initial probability associated with the presence of PT.
  
  
  CONCLUSIONS
  Since ADA is highly sensitive, we can practically exclude TB as the cause of effusion when there are low ADA values. However, to confirm the possibility of TB we recommend that other variables, such as prevalence of lymphocytes (higher than 90%), and high protein levels (more than 4 g/dL); low age (less than 45 years) also should be considered.
authors.affiliation: University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil. dduprat@unirio.br
authors.forename: Denise Duprat
authors.initials: DD
authors.lastname: Neves
authors.forename: Ricardo Marques
authors.initials: RM
authors.lastname: Dias
authors.forename: Antônio José Ledo Alves
authors.initials: AJ
authors.lastname: da Cunha
authors.forename: Paulo César Amorim
authors.initials: PC
authors.lastname: Preza
mesh_terms: D000243:Adenosine Deaminase / Q000032:analysis*; D000328:Adult; D000368:Aged; D001499:Bayes Theorem; D015415:Biomarkers / Q000032:analysis; D006801:Humans; D016013:Likelihood Functions; D018655:Lymphocyte Count; D008875:Middle Aged; D010996:Pleural Effusion / Q000737:chemistry / Q000201:enzymology*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014396:Tuberculosis, Pleural / Q000175:diagnosis* / Q000209:etiology
chemical_list: D015415:Biomarkers; D000243:Adenosine Deaminase