Retinol-binding protein 4 and plasminogen activator inhibitor-1 as potential prognostic biomarkers of non-allergic asthma caused by obesity in adolescents

Background: Non-allergic asthma caused by obesity is a complication of the low-grade chronic inflammation inherent in obesity. Consequently, the serum concentrations of adipokines such as retinol-binding protein 4 (RBP4) and plasminogen activator inhibitor-1 (PAI-1) increase. No gold standard molecule for the prediction of non-allergic asthma among obese patients has been identified. Objective: To evaluate RBP4 and PAI-1 as prognostic biomarkers of non-allergic asthma caused by obesity. Methods: A cross-sectional study between four groups of adolescents: (1) healthy (n = 35), (2) allergic asthma without obesity (n = 28), (3) obesity without asthma (n = 33), and (4) non-aller-gic asthma with obesity (n = 18). Results: RBP4 was higher in the non-allergic asthma with obesity group than in the obesity without asthma group (39.2 ng/mL [95% confidence interval (CI): 23.8-76.0] vs. 23.5 ng/mL [95% CI: 3.2-33.5], p < 0.01), and PAI-1 was higher in the non-allergic asthma with obesity group than in the obesity without asthma group (21.9 ng/mL [95% CI: 15.7-26.5] vs. 15.9 ng/mL [95% CI: 9.4-18.2], p < 0.05). Receiver operating characteristic (ROC) curve analysis demonstrated that the serum RBP4 cut-off value was >42.78 ng/mL, with an area under the ROC curve (AUC) of 0.741 (95% CI: 0.599-0.853, p = 0.001), considered acceptable. The PAI-1 cut-off value was >12.0 ng/mL, with an AUC of 0.699 (95% CI: 0.554-0.819, p = 0.008), considered fair. Conclusions: RBP4 may be useful to predict non-allergic asthma among obese adolescents in clinical practice.