Accuracy and Precision of Quantitative Calibrated Loops in Transfer of Bronchoalveolar Lavage Fluid

Abstract

Quantitative cultures of bronchoalveolar lavage (BAL) fluid are important in the diagnosis of ventilatorassociated pneumonia, and calibrated loops are commonly used to set up these cultures. In this study, the performances of calibrated 0.010-and 0.001-ml loops in the transfer of BAL fluid were determined. Five loops of one lot from seven manufacturers were tested. Calibrations were performed by the gravimetric method (0.010-ml loops) and the colorimetric method (0.001-ml loops). Most of the 0.010-ml loops displayed a precision that was less than 10%, but six of them showed very poor accuracies as they transferred a deficiency (nichrome loops) or an excess (disposable loops) of BAL fluid that exceeded ؎10%. The mean maximum and minimum BAL fluid volumes delivered by the 0.010-ml loops differed by a factor 3. The 0.001-ml loops displayed acceptable precision. Five of them showed inaccuracies of <؎10%, and mean maximum and minimum BAL fluid volumes had a range of a factor of 2. For all loops, the volumes of BAL fluid sampled were larger than the volumes of reagent-grade water sampled. Results of the colony counting experiments confirmed these findings and revealed a high intra-assay variability for the 0.001-ml loops. We conclude that, when BAL fluid samples are cultured with calibrated loops, (i) proper verification of the calibration of these loops is mandatory, (ii) calibrations should be performed with BAL fluid as the test solution, and (iii) borderline quantitative culture results should be interpreted with knowledge of the inaccuracy values of these loops.

Mimivirus is not a frequent cause of ventilator-associated pneumonia in critically ill patients

“…A total cell count was performed using a Fuchs Rosenthal haemocytometer chamber. Quantitative bacterial culture was performed as described previously [Jacobs et al, ]. Cytocentrifuged preparations [De Brauwer et al, ] were stained with May‐Grünwald Giemsa stain and Gram stain.…”

Soluble Triggering Receptor Expressed on Myeloid cells-1 in bronchoalveolar lavage fluid is not predictive for ventilator-associated pneumonia

“…All aliquots were pooled, except for the first one. The BALF samples were Gram-stained, and quantitative culture was performed as described previously [ 13 ]. The urea concentration was determined by means of an enzymatic conductivity rate method using the SYNCHRON LX System (Beckman Coulter BV, Mijdrecht, The Netherlands) as previously described [ 14 ].…”

Micro‐instillation of fluorescein with an inoculation loop for ocular surface staining in dry eye syndrome

“…Accuracy was expressed as the mean difference (in percentage) between expected and measured amounts (here, 1 ll). Precision was assessed by the agreement between repeated measurements, corresponding to intra-assay variability and expressed as the coefficient of variation (CV) (standard deviation/mean) of the replicates (Jacobs et al 2000).…”