Background The relationship between wheezing in infancy and future development of asthma has been under investigation for a long time. API is a widely accepted clinical index to define asthma risk. On the other hand, vitamin D was found to play a principal role in decreasing disease severity of asthma and other allergies.

Objectives To delineate the relationship between the serum level of vitamin D and asthma predictive index in wheezy infants.

Methods In this cross-sectional study fifty wheezy infants and thirty healthy controls of matched age and sex were included. Feeding history and exposure to environmental factors and were assessed through parents’ questionnaire. The clinical characteristics of the children were assessed as well as the asthma predictive index. The serum levels of vitamin D, Calcium and Phosphorus were measured in all patients. Correlation analysis was used to evaluate the relationship between homogeneously distributed variables.

Results Thirty-three of the fifty wheezy child (66%) were recurrent wheezers (had more than three wheezing attacks/year). The Asthma Predictive Index (API) was found to be positive in thirty two patients (64%). Serum Vitamin D was significantly lower in wheezy infants compared to control group as well as API (+ve) patients compared to API (-ve) patients (p=0.013, p<0.01 respectively).

Serum Vitamin D level showed significant (-ve) correlation with number of previous wheezing episodes (p<0.01).No significant difference was found between the API (+ve) group and API(-ve) group in terms of other laboratory markers (Calcium, Phosphorus and Eosinophil count).

Conclusions Vitamin D deficiency was found to be more prevalent in wheezy infants than controls, suggesting it might play an underestimated role in pathogenesis of wheezes in infants. We also suggest that serum vitamin D levels might be used as a biomarker for prediction of (+ve) API state, raising the possibility of having childhood asthma.