SESSION TYPE: Pleural Biomarkers
PRESENTED ON: Monday, October 22, 2012 at 04:00 PM - 05:30 PM
PURPOSE: Classifying pleural fluid as an exudate or transudate is crucial. Light's criteria, the current standard for distinguishing between the two, requires a blood draw with laboratory processing time, and is less reliable in patients taking diuretics. A previous study used reactive oxygen species present in most exudates to identify them. Researchers added a small amount of hydrogen peroxide to pleural fluid at the bedside. They excluded samples contaminated by blood, as well as patients with heart failure, limiting the study's applicability. Our study determines if these exclusion criteria are necessary to preserve the accuracy of the hydrogen peroxide test.
METHODS: Forty-two pleural fluid samples were checked for blood with Hemastix strips within 24 hours of collection. Regardless of the result, 20 microliters of hydrogen peroxide were added to 200 microliters of pleural fluid warmed to approximate body temperature. Formation of bubbles indicated an exudate. Two examiners confirmed bubble formation.
RESULTS: The 42 samples consisted of 11 transudates and 31 exudates per Light's criteria. There was diagnostic concordance between the H2O2 test and Light's criteria for 32 samples. Using Light's as the standard, there were 4 false exudates and 6 false transudates.
CONCLUSIONS: Our initial results are promising, with 76% diagnostic concordance between the H2O2 test and Light's criteria. Decay of oxidative species during processing delays could account for false transudates. Malignancy may also be a factor; all false transudates came from patients with cancer. Early on, we appreciated variation in vigor of bubble formation between samples. Samples with weaker reactions may have been transudates with minor sources of oxidative species, explaining the false exudates. We lack statistical power to comment on the significance of blood currently. However, over 30 samples were Hemastix positive, so exclusion of bloody fluid does not seem practical. Diuretics seem unimportant, as only 1 false exudate and 1 false transudate came from patients taking diuretics.
CLINICAL IMPLICATIONS: It may be possible to distinguish exudates from transudates using hydrogen peroxide rather than Light's criteria at the bedside.
DISCLOSURE: The following authors have nothing to disclose: Scott Kellie, Gregory Pfister, Jason Mann, Rodrigo Cavallazzi, Jinesh Mehta
We are investigating the usefulness of using hydrogen peroxide to differential transudative pleural fluid from exudative fluid.University of Louisville, Louisville, KY