Vitamin D Status and Asthma Control, Pulmonary Function, and Oxidative Stress in Adults With Bronchial Asthma (VD-ASTHMA)

This single-center cross-sectional observational study is designed to evaluate the association between serum vitamin D status and asthma-related clinical, functional, and biochemical characteristics among adult patients with bronchial asthma.

Eligible participants will be adults aged 18 years or older with confirmed bronchial asthma who are clinically stable at the time of assessment. Participants will be recruited from Abbassia Chest Hospital, Cairo, Egypt.

After obtaining written informed consent, demographic and clinical characteristics will be collected, including age, sex, body mass index (BMI), smoking status, asthma duration, previous exacerbations, hospitalization history, asthma severity, and current asthma medications including inhaled corticosteroids (ICS), long-acting β2 agonists (LABA), and short-acting β2 agonists (SABA).

Asthma control will be assessed using the Asthma Control Test (ACT), which evaluates symptom frequency, rescue medication use, activity limitation, and patient perception of asthma control.

Pulmonary function will be evaluated using post-bronchodilator spirometry according to ATS/ERS recommendations. The recorded parameters will include forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio.

Blood samples will be collected for serum 25(OH)D measurement using the DiaSorin LIAISON® 25 OH Vitamin D chemiluminescent immunoassay and assessment of oxidative stress biomarkers in erythrocyte hemolysates, including MDA, SOD, GPx, and GSH.

Participants will be classified according to vitamin D status:

Vitamin D deficient: <20 ng/mL Vitamin D insufficient: 20-30 ng/mL Vitamin D sufficient: >30 ng/mL

The primary objective is to determine whether serum vitamin D concentration is associated with asthma control. Secondary objectives include evaluating associations with pulmonary function and oxidative stress biomarkers.