Cut-off values and significance of Oil Red O-positive cells in bronchoalveolar lavage fluid

Objective: To evaluate the percentage and predictive value of Oil Red O-positive macrophages (ORO-PM) to identify lipid-laden macrophages in bronchoalveolar lavage fluids (BALF) from patients with different pathologies. Methods: The percentage and absolute numbers of ORO-PM were evaluated in 305 BALF. The patients were separated into ten groups: corticosteroid treatment (n = 18), amiodarone treatment (n = 8), interstitial fibrosis (n = 11), human immunodeficiency virus (HIV)-positive (n = 25), infectious pneumonia (n = 43), severe haematological disorder (n = 25), interstitial syndrome (n = 109), suspicion of cancer (n = 17), transplant recipients (n = 50) and controls (n = 43). The total and differential cell counts in BALF were recorded. The presence of specific pathogens was also noted. Parametric and non-parametric tests were used to compare the values between groups. Receiver-operating characteristics (ROC) curves were established in order to determine a cut-off value. Results: The percentages of ORO-PM were (mean +/- standard deviation) 21.67 +/- 29.12 in the corticosteroid group, 10.00 +/- 12.49 in the amiodarone group, 19.45 +/- 20.72 in the interstitial fibrosis group, 47.80 +/- 30.46 in the HIV group, 19.72 +/- 26.26 in the infectious pneumonia group, 27.42 +/- 30.04 in the severe haematological disorder group, 25.18 +/- 30.63 in the interstitial syndrome group, 17.64 +/- 27.76 in the suspicion of cancer group, 22.50 +/- 27.27 in the transplanted recipients group and 2.63 +/- 3.48 in the control group. Significantly higher values were found in all groups when compared with the control group (P < 0.001). Only the HIV group showed higher numbers of ORO-PM when compared with the interstitial syndrome group (P < 0.01). According to ROC curves, > 6% ORO-PM was suggested as the positive cut-off value. Conclusion: Significantly increased numbers of ORO-PM were associated with various lung pathologies. However, the higher numbers observed in HIV patients require further investigations.