The cost and diagnostic efficacy of microbiological evaluation of exudative pleural effusion

Purpose: To evaluate the cost and diagnostic efficacy of microbiological studies of pleural fluids. Method: Hospitalized patients with exudative pleural effusion were prospectively evaluated. The fluid samples were examined for Gram stain, acid-fast bacilli smear together with specific bacterial, fungal and mycobacterial cultures. Results: Bacteriologic and EZN stains of the pleural fluids were negative in 89 cases included whereas fluid cultures were positive in 9 (10,1%) cases [3 (12,5%) of the 24 with tuberculous pleurisy and 6 (28,5%) of the 21 with empyema or other parapneumonic pleural effusion]. The cultures of the malignant, nonspecific and paramalignant fluids were negative. In cases with empyema or other parapneumonic pleural effusion and tuberculous pleurisy, no significant difference was determined between culture-positive and culture-negative cases regarding age, gender, fever or fluid LDH and glucose levels; positive cultures were more frequent in the presence of fluid purulence (55.6% versus 8.3%, p=0.046). In 5 (83.3%) of the 6 culture-positive and in 6 (40%) of the 15 culture-negative cases with empyema or other parapneumonic effusion, change in antibiotic treatment was necessary. The costs of the microbiological studies was 39.4 Euro for each case and 1735 Euro and 1419 Euro for cases with noninfectious and infectious fluids, respectively. Conclusion: Diagnostic yield of the routine microbiological studies of pleural fluids was determined low. It was concluded that requesting microbiological studies of pleural fluids in cases strongly considered to have infection on clinical basis and/or in cases with purulent fluid would be more beneficial regarding diagnostic yield and cost.