Perceptions vs. reality: measuring of pleural fluid pH in North Carolina.

Background: Pleural fluid pH anaerobically handled and measured by a blood gas analyzer (BGA) is used to define a pleural space infection as complicated and predict the life expectancy of patients with malignant pleural effusions. Pleural fluid pH can also be measured by other less accurate methods. It is unknown whether physicians who use pleural fluid pH measurements are aware of the method used by their laboratories.

Methods: We surveyed 90 pulmonary physicians in North Carolina about their use of pleural fluid pH and their hospital laboratory's approach (pH indicator stick, pH meter, or BGA). We then contacted their hospital laboratories to determine the actual method of pH measurement.

Results: Twenty-eight (31%) pulmonologists in 11 North Carolina hospitals responded on their use of pleural fluid pH. Of the 20 pulmonologists who order pleural fluid pH, 90% reported that their hospital measures pleural fluid pH via BGA, but the majority (72%) were inaccurate. Only two of 11 hospitals reported that they measure pleural fluid pH with a BGA.

Conclusion: Almost two-thirds of the chest physicians that order pleural fluid pH to help manage pleural effusions were using information that is not substantiated by the literature and, despite previous reports, hospitals still use suboptimal methods to measure pleural fluid pH. Further information is needed concerning the barriers to physicians and laboratory practices concerning the use of BGA for the measurement of pleural fluid pH.