Avaliação da cultura quantitativa e do gram graduado do lavado broncoalveolar no diagnóstico das pneumonias nosocomiais

Abstract

The bacteriologic diagnosis of the Nosocomial Pneumonia (NP) is very difficult, once there isn’t a simple, efficient, sensible, specific or reasonable method. Many scientists have been researching bronchoscopic methods such as the study of the Bronchoalveolar Lavage (BAL) and the use of the Protected Specimen Brush (PSB) to gather samples of bronchic secretion. This study tried to determine a cut off of the quantitative culture of BAL which would show a better specificity and sensitivity for the bacteriologic diagnosis of the NP, as well as the evaluation of BAL by the color of Gram, through a system of grading with three predetermined parameters, which were: Polimorphonuclears > 10/field, Bactérias > 10/field and intracellular microorganisms > 1%. During the period of April to December, 1996, 80 adult patients have been evaluated. Thirty of them were no infected and the other 50 suffered fforn other diseases, different from NP. The cut off of the quantitative culture of BAL, which was above or equal to IO3 colony formation unit (CFU)/ml showed a sensitivity of 66% and a specificity of 86%. The Positive Predictive Value (PV+) was 74.1%, and the Negative Predictive Value (PV-) was 81.1%. These results were greater than the ones shown with the cut off of 103 CFU/ml. For the cut off > IO25 CFU/ml, the main isolated bactérias were, in a decreasing order : P. aeruginosa, S.aureus, K. Pneumoniae, P.Mirabilis, among others. The analysis of the Graduated Gram (GG) related to the clinicai diagnosis of NP showed that the presence of at least two criterions of the GG determined a sensitivity of 43%, and a specificity of 96%, PV+ = 86% and PV- = 78.2%. When we consider 3 parameters of the GG, we will get a sensitivity of 10%, but a specificity of 100%. PV+ = 100% and PV- = 64%. When we correlated at least two of the predetermined parameters of the GG with the growing of the quantitative culture of BAL of a cut off > 105 CFU/ml, we found a sensitivity of 51.9% and a specificity of 98.1%. PV+ = 93.3% and PV- = 80%. When we evaluated the three predetermined parameters of the GG, the sensitivity dropped to 11.1%, keeping the specificity at 100%, PV+ = 100% and PV- = 68%. The results show that the GG is a precocious indicator of NP, and that it also give us a clue of the feasible bacterian etiology. The cut off > 10'' CFU/ml of BAL. improved the specificity of the bacteriological diagnosis of NP.