Assessment of neutrophil gelatinase-associated lipocalin and lactate dehydrogenase in peritoneal fluids for the screening of bacterial peritonitis.

BACKGROUND: Manual microscopy remains the gold standard for enumeration and classification of nucleated cells in peritoneal fluids, especially for diagnosing bacterial peritonitis. However, this approach carries several drawbacks, so that the use of simple and automated tests may be a viable option for initial screening of peritoneal fluids. MATERIALS AND METHODS: Neutrophil gelatinase-associated lipocalin (NGAL), lactate dehydrogenase (LDH), proteins and glucose were assessed in peritoneal fluids from patients with new onset nonmalignant ascites, along with nucleated cell count and differentiation. RESULTS: One hundred and eleven specimens were analyzed, 26 of which (23%) with polymorphonuclear leukocyte (PMN) count≥250/μL, thus compatible with bacterial peritonitis. The median concentration of LDH and NGAL was 3.4 and 3.7-fold higher in samples with ≥250PMN/μL. The concentration of proteins was also higher in samples with ≥250PMN/μL, whereas that of glucose was lower. The PMN count significantly correlated with peritoneal fluid values of LDH (r=0.859), NGAL (r=0.774) and proteins (r=0.268), but not with glucose (r=-0.069). The area under ROC curve was 0.88 for LDH, 0.89 for NGAL and 0.94 for their combination (both tests positive), whereas that of proteins and glucose was 0.80 and 0.71, respectively. Sensitivities and specificities were 0.81 and 0.87 for LDH≥227U/L, 0.96 and 0.75 for NGAL≥120ng/mL, 0.77 and 0.95 for their combination. The agreement with PMN count was 0.86 for LDH, 0.80 for NGAL, and 0.91 for their combination. CONCLUSIONS: These results suggest that assessment of NGAL in peritoneal fluids, especially in combination with LDH, may be a reliable approach for screening of bacterial peritonitis in patients with new onset nonmalignant ascites.