Pleural fluid interleukin-8 and C-reactive protein for discriminating complicated non-purulent from uncomplicated parapneumonic effusions

Respirology. 2008 Jan;13(1):58-62. doi: 10.1111/j.1440-1843.2007.01189.x.


Background and objective: This study was designed to test the hypothesis that measurement of IL-8 and CRP in pleural fluid could improve the identification of patients with non-purulent parapneumonic effusions that ultimately require chest tube drainage.

Methods: We assessed IL-8, CRP and three classical parameters (pH, glucose and LDH) in the pleural fluid of 100 patients with parapneumonic effusions. Forty-nine of these patients had non-purulent complicated effusions (complicated parapneumonic pleural effusion, CPPE), and 51 had uncomplicated parapneumonic pleural effusions (UPPE). Receiver-operating characteristic curves were used to assess the sensitivity and specificity of pleural fluid biochemical parameters for differentiating among the two patient groups. IL-8 production was determined using a commercially available ELISA kit, and CRP was measured by immunoassay.

Results: At a cutoff value of 1000 pg/mL, IL-8 differentiated CPPE from UPPE with a sensitivity of 84% and a specificity of 82%. Likewise, CRP levels were higher in CPPE than in UPPE, and showed 72% sensitivity and 71% specificity at a cutoff value of 80 mg/L. We found that all five pleural fluid tests showed similar diagnostic accuracies when evaluated by receiver-operating characteristic analysis. However, multivariate analysis indicated that the size of the effusion, as well as pleural fluid pH and IL-8 concentration, were the best discriminatory parameters, with likelihood ratios of 6.4, 4.4 and 3.9, respectively.

Conclusions: Pleural fluid IL-8 is an accurate marker for the identification of non-purulent CPPE.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • C-Reactive Protein / metabolism*
  • Community-Acquired Infections / complications
  • Community-Acquired Infections / diagnosis
  • Community-Acquired Infections / metabolism
  • Diagnosis, Differential
  • Female
  • Humans
  • Interleukin-8 / metabolism*
  • Male
  • Middle Aged
  • Pleural Effusion / etiology
  • Pleural Effusion / metabolism*
  • Pleural Effusion / pathology
  • Pneumonia, Bacterial / complications
  • Pneumonia, Bacterial / diagnosis*
  • Pneumonia, Bacterial / metabolism
  • Predictive Value of Tests
  • ROC Curve
  • Suppuration / diagnosis
  • Suppuration / etiology
  • Suppuration / metabolism


  • Interleukin-8
  • C-Reactive Protein