Low value of adenosine deaminase in tuberculous pleural effusions

It has been claimed that a value of adenosine deaminase (ADA) activity lower than 43 U·/·1 excludes tuberculous aetiology of pleural effusion [1, 2]. We report nine cases of tuberculous pleurisy with at least one determination of ADA (by Giusti and Galanti) activity less than 43 U-/·1 , and two other cases with an ADA value below 44 U-/·1 , out of 114 ADA determinations (representing 8% or 10%). The tuberculosis diagnosis was confirmed by bacteriological cultures of pleural fluid or biopsy material and the pathological finding of a granulomatous lesion in the pleural tissue. In the literature we have found eighteen cases of tuberculous pleurisy with an ADA activity value <43 U·/·1 [35]; however, among the largest series of ADA and tuberculosis no cases with a value of ADA activity <43 U-/·1 were described [1, 2, 6] . In five of the nine cases reported with low ADA activity values, a second determination a few days later evidenced a rise in the ADA activity over 43 U·/'1 to values well within the range of tuberculous effusion (fig. 1). In another two cases a second ADA determination six and eight days later, respectively, still showed a value below 43 U·/·1. In the last two cases only one determination was obtained.