Abstract
BackgroundAlthough pleural fluid lactate dehydrogenase (LDH) and adenosine deaminase (ADA) levels are often used to distinguish between tuberculous pleural effusion (TPE) and parapneumonic pleural effusion (PPE), this can be challenging as the LDH level may vary from normal to severely increased in PPE and a significantly elevated ADA is frequently measured in both conditions. In this study, we evaluated use of the pleural fluid LDH/ADA ratio as a new parameter to discriminate TPE from PPE.MethodsA retrospective study was conducted in patients with pathologically-confirmed TPE (n = 72) and PPE (n = 47) to compare pleural fluid LDH and ADA levels and LDH/ADA ratios between the 2 groups. A receiver operating characteristic (ROC) curve was constructed for identifying TPE.ResultsThe median pleural fluid LDH and ADA levels and LDH/ADA ratios in the TPE and PPE groups were: 364.5 U/L vs 4037 U/L (P < .001), 33.5 U/L vs 43.3 U/L (P = .249), and 10.88 vs 66.91 (P < .0001), respectively. An area under the ROC curve of 0.9663 was obtained using the LDH/ADA ratio as the indicator for TPE identification, and the sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were, respectively, 93.62%, 93.06%, 13.48, and 0.068 at a cut-off level of 16.20.ConclusionsThe pleural fluid LDH/ADA ratio, which can be determined from routine biochemical analysis, is highly predictive of TPE at a cut-off level of 16.20. Measurement of this parameter may be helpful for clinicians in distinguishing between TPE and PPE.
Highlights
Pleural fluid lactate dehydrogenase (LDH) and adenosine deaminase (ADA) levels are often used to distinguish between tuberculous pleural effusion (TPE) and parapneumonic pleural effusion (PPE), this can be challenging as the LDH level may vary from normal to severely increased in PPE and a significantly elevated ADA is frequently measured in both conditions
The pleural fluid LDH/ADA ratio, which can be determined from routine biochemical analysis, is highly predictive of TPE at a cut-off level of 16.20
As different mechanisms contribute to the elevation of ADA and LDH, it may be helpful to differentiate TPE from PPE by examining the pleural fluid LDH/ADA ratio, which has not been investigated in previous studies
Summary
Pleural fluid lactate dehydrogenase (LDH) and adenosine deaminase (ADA) levels are often used to distinguish between tuberculous pleural effusion (TPE) and parapneumonic pleural effusion (PPE), this can be challenging as the LDH level may vary from normal to severely increased in PPE and a significantly elevated ADA is frequently measured in both conditions. We evaluated use of the pleural fluid LDH/ADA ratio as a new parameter to discriminate TPE from PPE. An elevated pleural fluid LDH may present in TPE, PPE, and MPE, and the level is likely to range greatly from normal to extremely increased, which limits the use of LDH for identifying PPE in an individual patient due to the low sensitivity [9, 13, 14]. It remains a challenge for clinicians to distinguish between patients with TPE and PPE from elevated pleural fluid ADA and LDH levels. As different mechanisms contribute to the elevation of ADA and LDH, it may be helpful to differentiate TPE from PPE by examining the pleural fluid LDH/ADA ratio, which has not been investigated in previous studies
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