Repeatability of cellular constituents and cytokine concentrationin fluid obtained by non-bronchoscopic bronchoalveolar lavage ofinfants receiving extracorporeal oxygenation

摘要

BACKGROUND—Since few studies have assessed the repeatability of non-bronchoscopic bronchoalveolar lavage (NB-BAL), we compared cellular counts and cytokine concentrations in fluid obtained by standardised NB-BAL from each side of 20 intubated infants receiving extracorporeal membrane oxygenation (ECMO).
METHODS—Total cell counts were obtained from 95 paired lavages and 77 pairs were suitable for differential counts and measurement of cytokine concentrations.
RESULTS—Moderate correlation was noted between the two sides for most cell types including total cell counts and percentages of neutrophils and macrophages (R=0.70-0.84) and for cytokine concentrations (IL-8 R=0.78, IL-6 R=0.75, TNF-αR=0.64, all p⩽0.001). Using Bland-Altman analysis the mean difference between the two sides approached zero for cellular constituents (total cell counts mean difference 1.7, limits of agreement -187.5 to +190.9 × 10⁴/ml; percentage neutrophils -3.9%, -41.5% to +33.6%; percentage macrophages 3.9%, -33.8% to +41.6%) but tended to be greater on the right forlogarithmically transformed cytokine measurements (IL-8: left/rightratio 0.74, limits of agreement 0.12 to 5.45,IL-6: 0.93, 0.09 to 5.87, and TNF-α: 0.93, 0.27 to 3.16). Using linear regression with randomeffects to assess the variability, only the infant's age appearedto influence the cellular results but, for cytokines, only the volumeretrieved affected the variability. The magnitude of the measurements,the underlying disease, the operator's experience, days onECMO, or survival did not affect the variability.
CONCLUSION—Measurementsobtained by NB-BAL need to be interpreted with caution and stronglysuggest that normalisation for the dilutional effects of saline is essential.