PLEURAL FLUID ADENOSINE-DEAMINASE AND LYMPHOCYTE PROPORTION - CLINICAL USEFULNESS IN THE DIAGNOSIS OF TUBERCULOSIS

Adenosine deaminase (ADA) and lymphocyte proportion are known to be in dependently elevated in tuberculous effusions, but are non-specific, a nd false positive results are frequent. To overcome this problem the c ombined use of both parameters was prospectively studied in 276 patien ts with pleural effusion seen at Porto Alegre, Brazil. Using a cut-off level of 40 U/l at 37-degrees-C (method of Giusti19) for ADA activity and lymphocyte proportion of more than 50%, the correct diagnosis of tuberculosis (sensitivity) was made in 90.7% (CI 87.3-94.1%) of 54 pat ients. A specificity of 97.7% (CI 95.9-99.5%) was recorded. Five false positive diagnoses of tuberculous effusion were made. Five false nega tive diagnoses were made: three cases with haematogenous tuberculous d issemination with low ADA levels, and two other patients with low lymp hocyte proportion. The combined use of ADA activity determination and lymphocyte proportion is a highly efficient diagnostic strategy of low cost, that merits wider use.