Assessement whether C-reactive protein (CRP) in pleural fluid, is a sensitive marker for discriminating transudative from exudative pleural effusions; to evaluate it can be used to distinguish inflammatory pleural effusions from malignant ones.
We studied 73 patients with pleural effusion. The diagnose was established by clinical features, laboratory tests and pleural biopsy. Concentrations of CRP in the pleural fluid were measured using an tabidometric assay. We assessed sensitivity, specificity, positive and negative predictive value and accuracy of the test. We use Student's paired t-Test with a two-tailed distribution and chi square (r-value) to evaluate significance (P<0.05).
Pleural fluid CRP levels were significantly lower in the transudate group than exudates effusions (5.5± 4.9 mg/L and 29.9 ± 26.5 mg/L respectively) When the pleural fluid CRP level was < 15 mg/L, the sensitivity was 94.7%. Specificity 60.2%, accuracy 68.9% negative predictive value 97.1%The parapneumonic effusion CRP levels (mean 52.9 ± 33.7 mg/L) were significantly higher than those with neoplastic and tuberculous pleurisy The neoplastic effusion CRP levels (11.7±9 mg/L) were significantly lower than parapneumonic tuberculous and chronic non-specific pleurisy In six cases, with neoplastic effusions we found lower liquid CPR (6.28 ± 4.4 mg/L) and higher liquid ADA level (57.5 ± 33.2 U/L). The ratio between pleural fluid and serum CRP was significantly lower in the neoplastic effusion (0. 36 ± 0.15 mg/L) than tubercular and chronic non-neoplastic pleurisy respectively (0.65±0.33) and (0.6±0.3).Pleural fluid CRP levels < 20 mg/L had a sensitivity of 78%, specificity 66.6% a positive predictive value of 60.9% negative predictive value 81.8% and accuracy 69% for malignant effusion.
Pleural CRP-levels is useful marker in diagnosis of pleural effusion. Lower level of CRP obtained in the lymphocyte exudates group with high level of adenosine deaminase more than 40U may be a strong suggestion for neoplastic effusion.
Low values of CRP in exudate pleural lymphocitic effusion with low or high level of adenosine deaminase suggest strongly the diagnosis of malignant effusion.
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