Laboratory Test Reference Guide

<30 U/L - not strongly suggestive of tuberculous
effusion. However, other clinical findings should also be considered as its
negative predictive value is not very high especially in intermediate to high
clinical pretest probability situations.

30- 70 U/L- borderline range, value of indeterminate significance. Specificity
for tuberculosis is significantly improved if the effusion is lymphocytic and
empyema is excluded.

>70 U/L- highly suggestive of tuberculosis. Note that high levels can also
be seen in empyema, lymphoma and rheumatoid effusion.

Adenosine deaminase is used in the diagnosis of
tuberculous pleural effusion. Adenosine deaminase has an important role in vivo
in the differentiation of lymphoid cells (pre-dominantly T-lymphocytes) and is
most abundant in lymphocytes.

Elevated levels of adenosine deaminase are also found in empyema, rheumatoid
pleuritis, lymphoma and post-CABG pleural effusions.

Specificity is increased if there is also a lymphocyte to neutrophil ratio of
>0.75.

Adenosine deaminase levels can also be measured in pericardial effusion and
ascitic fluid but this request should be discussed with a chemical pathologist
prior to sample collection (ext 8520 or 8599).

The range of Adenosine deaminase in CSF is lower than the testing range for our
assay thus we are not offering this test for CSF at this stage.

Middlemore Hospital Laboratory