Objective: Protected specimen brush (PSB) and bronchoalveolar lavage (BAL) are proposed in combination to optimize antimicrobial treatment. Nevertheless, they are only validated for immediate laboratory processing. This study was therefore conducted to determine whether 48 h conservation at a mere 4 degrees C enables good culture reproducibility for both PSB and BAL.
Design and setting: Prospective study, evaluation of a conservation procedure for PSB and BAL, from February 1994 to February 1995, in the 12 bed ICU of a general hospital (938 beds).
Samples: Ninety-nine PSB and 86 BAL samples, obtained from 100 bronchoscopic procedures, were analyzed. Thresholds were 10(3) and 10(4) cfu/ml for PSB and BAL, respectively.
Measurements and results: Qualitative comparison between the immediate and 48 h procedures were, for PSB, specificity 100%, sensitivity 78%, positive predictive value 100%, negative predictive value 84% and overall accuracy 90%; and for BAL: 100%, 89%, 100%, 89% and 94%. Lowered 10(2) and 10(3) cfu/ml thresholds at the 48 h procedure for PSB and BAL reduce the false negatives from 10 to 3 and 5 to 1, respectively. Microorganism results were comparable for PSB and BAL ( r = 0.63 and 0.67), especially for the most resistant strains: Staphylococcus, Enterobacteriaceae and Pseudomonas. However, there was a decrease in the Neisseria and Haemophilus group ( p < 0.01).
Conclusion: There is a good culture reproducibility for both PSB and BAL after 48 h conservation at 4 degrees C, especially with lowered thresholds; this technique is therefore appropriate for routine use.