Objective: To investigate the relation of circulating Fatty acid binding protein 4 (FABP4) molecule with asthma, severity of asthma, and eosinophil and neutrophil counts in the peripheral blood as well as to evaluate the potential risk factors including demographic and clinical features for severe asthma.

Materials and Methods: Sixty-seven patients older than 18 years of age with asthma and 20 healthy controls were included in the study. Patients were grouped as those with severe (n=34) and non-severe (n=33) asthma. Additional analysis was performed depending on the peripheral eosinophil count.

Results: The mean age of the patients was 42.37 ± 11.26 years and 77.6% of them were female. In severe asthmatic patients, the mean age and the presence of house dust mite allergy and familial history of asthma were higher, and the actual asthma control test (ACT) score was lower than in the non-severe asthma group (p<0.001, p=0.005, p=0.001, p<0.001). Neutrophil counts and serum total IgE levels were higher in patients with severe asthma than those with non-severe asthma (p<0.001, p=0.02). According to multivariate analysis, age and familial history of asthma were associated with severe asthma (p=0.003, p=0.008). FABP4 levels were not different between the three groups and there was no correlation between serum FABP4 levels and eosinophil counts; however, a positive correlation was observed between FABP4 levels and neutrophil counts (p>0.05; r=0.106 p>0.05; r=0.4, p=0.001).

Conclusion: Circulating FABP4 levels were not related to asthma, severity of asthma, or peripheral eosinophil count but may reflect neutrophilic asthma.