Extremely High Pleural Effusion ADA Levels in the Diagnosis of Tuberculous Pleurisy

Pleural fluid adenosine deaminase (ADAPF) activity is increased in effusions caused by certain clinical conditions including tuberculosis and bacterial infections. A cut-off value above 70 U/L for ADA in the diagnosis of tuberculosis pleurisy (TBpl) has been discussed. However, the high cut-off levels for ADAPF (＞ 70 U!) in the diagnosis of TBpl have not been established. From Jan. 2000 to Oct. 2002, 3144 pleural effusion specimens were sent to our department for ADA measurement. Two hundred and seventy-nine cases with an ADA level higher than 70 U/L were classified into three groups: tuberculous pleurisy (N=143), empyema thoracis (N=77), and neither of the above (N=59). When pleural effusion was lymphocytic, the sensitivity and specificity for TBpl were increased depending on the levels of ADA (Table 2). The specificity for TBpl was 100% when ADAPF was over 140 U/L. In conclusion, the combined use of a high cut-off level for ADAPF and a lymphocyte proportion would eliminate the need for invasive studies and be useful in the differential diagnosis.