Accuracy of delayed cultures of plugged telescoping catheter samples for diagnosing bacterial pneumonia

Objective: It is not always feasible to culture immediately bacteriologic s amples of protected pulmonary specimens on a 24-hr basis before starting an tibiotic treatment. We have evaluated the effect of delaying the culture of immediate plugged telescoping catheter (PTC) samples performed before star ting antibiotherapy. Design: Prospective paired comparisons study. Setting: Intensive care unit in a university hospital. Patients: Ninety-nine PTCs were performed on 68 intensive care unit patient s suspected of nosocomial or community-acquired bacterial pneumonia. Intervention: PTC samples were divided into two aliquots: one for immediate (H0) analysis and one for storage at 4 degreesC (H24) for 24 hrs before be ing cultured. Measurements and Main Results: The results from these delayed cultures (H24 ) were compared with those from immediate ones (H0), All negative H0 sample s (n = 59) were also negative at H24. Forty PTCs yielded one or more microo rganisms, with a total of 69 microorganisms in one or both samples. H0 and H24 cultures were concordant in 119 of 128 (97.9%) cases (kappa coefficient value 0.79) with a threshold of 10(3) colony-forming units (cfu)/mL. Agree ment between paired cultures was very goad. The bias calculated as the mean difference between paired culture results was 0.128 +/- 1.024 (Delta log). Concordance using the 103 cfu/mL threshold (102/107 cases, kappa coefficie nt value 0.82) and agreement were enhanced (0.067 +/- 0.645) when possible contaminants were excluded (n = 21). Conclusions: Storing PTC specimens for 24 hrs at 4 degreesC is an acceptabl e alternative when culturing cannot be performed immediately. This allows s tarting antibiotic treatment without any delay.