Background Cystic fibrosis (CF) is an inherited genetic disorder, clinical characterised by respiratory failure due to chronic pulmonary infection and pancreatic insufficiency. Malabsorption of fat-soluble vitamin leads to low level of vitamin A, D, E and K. It is already well know how vitamin D influences the immune response. Recent studies show the role of vitamin D on lung function in patients with cystic fibrosis.

Aim to evaluate the correlation between vitamin D level and pulmonary function in cystic fibrosis’s children.

Methods We design an observational study based on the evaluation of 59 children with cystic fibrosis. Biochemical assessment of every patient included dosage of 25-OH cholecalciferol levels, not related to season. Deficiency was defined as vitamin D level<30 ng/ml. Patients with chronic severe infections influencing the lung function were excluded. Spirometry was performed by 30 patients (over 7 years old), using as significant variables forced expiratory volume in 1 st sec (FEV1), forced vital capacity (FVC) and forced expiratory flow 25%–75% (FEF 25–75). We correlated the vitamin D level and spirometry results, using the Pearson correlation coefficient (r).

Results From fifty-nine patients, 56.6% of patients performed spirometry, of which 56.6% had vitamin D level determined. The majority of our patients (92.3%) had low levels of vitamin D, almost one third (23.0%) having severe deficiency of vitamin D. Comparing Vitamin D level with FEV1 we obtained an insignificant statistic correlation (p>0.05) and the correlation coefficient was r=−0.016, FVC: r=0.16 and for FEF25-75: r=−0.06.

Conclusions In our study group an important percentage of vitamin D deficiency was found, despite regular vitamin supplementation. No statistical correlation was found between vitamin D level and spirometry results. A part of patient’s with ventilatory dysfunction had severe deficiency in vit. D. Measure must be instituted for an increase vit. D supplementation and subsequent improvement of lung function in our patients.