Measuring alveolar lavage fluid surfactant by fluorescence polarization.

We describe a procedure by which surfactant/albumin ratios in bronchoalveolar fluid (BALF) may be quantified with the Abbott Laboratories TDx fluorescence polarization analyzer and fetal lung maturity reagents. Adding albumin to BALF samples shifted the surfactant/albumin ratios to within the analytical range of the method. The analytical CV for assay of modified BALF samples was 2.9%. Ratios obtained for modified samples from normal individuals (n = 10), transplanted lungs (n = 23), and contralateral native lungs of the transplant recipients (n = 23) were significantly different (P = 0.006). The ratio obtained for these modified samples can be converted, if needed, to the ratio in the original sample by using a simple mathematical relationship and the albumin concentration of the sample. We propose that this ratio will be useful in evaluating the surfactant status of BALF, particularly in lung allografts.