Utility of measurement of interleukin-1ß and interleukin-8 in the diagnosis of complicated parapneumonic pleural effusions.

OBJECTIVES Thirty percent of patients with pneumonia develop pleural effusion, and of these, 20% have complicated effusion (CPPE), which may require a chest tube or surgery for resolution. The objective of the study is to compare the diagnostic yield of determining interleukin-1β and interleukin-8 in pleural fluid (PF) (PFIL-1β and PFIL-8) with respect to classic criteria (pH <7.2, lactate dehydrogenase [LD] >1,000 IU/mL, and/or glucose <60 mg/dL) in the early diagnosis of CPPE. METHODS Of the 559 patients studied, 40 had CPPE. All underwent PF analysis: pH, glucose (PFGLUC), LD (PFLD), PFIL-1β and PFIL-8, and PF/serum ratios (PF/SIL-1β and PF/SIL-8). RESULTS The diagnostic criterion that showed the best area under the curve was the combination of PF/SIL-8 and PFIL-1β (0.906), with a statistically significant difference (P < .05) compared with the classic criterion of pH and PFGLUC or PFLD (0.826). The combination of PF/SIL-8 and PFIL-1β (cutoffs >5.73 and >9.14 pg/mL, respectively) was significantly more sensitive (72.7%) and more specific (97.9%) (P < .05) than the rest of the parameters used. CONCLUSIONS Measurement of IL-1β and IL-8 in pleural fluid may be useful in the early diagnosis of CPPE, although individually, it may not improve the results obtained with the PFLD. Further studies are needed to more firmly establish what role these new parameters can play in the diagnosis of CPPE.