Objective To compare serum folate levels between atopic asthmatics, non-atopic asthmatics, and healthy controls.
Methods This case-control study included 60 asthmatics with at least one positive skin prick test (SPT) reaction (atopic asthma group), 60 asthmatics with negative SPT reactions (non-atopic asthma group), and 60 healthy controls with no history of asthma or other allergic diseases, and with negative SPT reactions. Serum folate and total IgE levels were measured in all subjects. In addition, lung functions were assessed by spirometry.
Results Serum folate levels were significantly lower among the atopic asthma group [9.1 (4.9, 12.1) ng/mL] as compared to the non-atopic asthma group [11.3 (7.5, 14.8) ng/mL] and the control group [12.0 (8.3, 15.1) ng/mL], p= 0.001. Among atopic asthmatics, serum folate levels were inversely correlated with total serum IgE levels (r=-0.483, p<0.001), and the number of positive SPT reactions (r=-0.442, p<0.001). Atopic asthmatics with a total serum IgE ≤200 IU/mL had significantly higher levels of serum folate than those with a total serum IgE >200 IU/mL. Regression analysis showed that higher folate levels independently predicted lower total serum IgE levels. Folate was not found to be an independent predictor of asthma. No association was observed between serum folate levels and values of forced expiratory volume in 1s.
Conclusion Among asthmatics, serum folate levels are significantly lower among atopics, and correlate inversely with the degree of atopy.