Diagnostic value of BAL fluid cellular profile and enzymes in infectious pulmonary disorders

Determination of the cellular profile of bronchoalveolar lavage fluid (BALF), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) appeared to be useful in monitoring pulmonary damage. The aim of this study was to investigate whether the cellular profile, LDH, its isoenzyme pattern and/or ALP in BALF are useful in the diagnostic work-up of patients with suspected pneumonia. The BALF specimens of 80 patients were studied. Group I consisted of patients with a pulmonary infection (n=33) and group II of patients,without signs of a pulmonary infection (n=47). Differentiation between these two groups was based upon the results of microscopy and quantitative cultures. The absolute as well as relative numbers of polymorphonuclear neutrophils (PMNs) was significantly higher in group I compared to group II (P<0.0001). The absolute number of PMNs showed a sensitivity of predicting the correct group of 95.7% and a specificity of 84.8%. The LDH activity in BALF was significantly higher in group I than in group II (p<0.0001). The LDH4/LDH5 ratio in BALF was lower in group I compared to group II (p<0.0001) and appeared to be the best discriminator between the two groups with a sensitivity of 93.6% and a specificity of 93.9%. In conclusion, the number of polymorphonuclear neutrophils as well as the lactate dehydrogenase activity, particularly its isoenzymes, in bronchoalveolar lavage fluid appeared to be of potential practical value to distinguish between infectious and noninfectious pulmonary disorders.