METHODS: All patients undergoing an initial diagnostic thoracentesis over 18 months with Pf lactate measured using a calibrated point-of-care blood gas analyzer were assessed.
RESULTS: The diagnoses of the enrolled patients (n = 170) included TBE (n = 49), PPE (n = 47), malignancy (n = 63), and transudate (n = 11). Pf lactate level in TBE, median 3.70 (inter-quartile range 2.65-4.90) mmol/l, was significantly lower than in PPE and CPPE. In the subgroup of TBE and CPPE patients whose initial Pf pH and glucose could suggest either condition, Pf lactate was significantly higher in those with CPPE. Pf lactate (cutoff ≥7.25 mmol/l) had a sensitivity of 79.3%, specificity 100%, positive predictive value 100%, and negative predictive value 89.1% for discriminating CPPE from TBE (area under the curve 0.947, p