An observational study in Bronchiolitis Acute, Wheezing and RSV, sponsored by National and Kapodistrian University of Athens. Active, not recruiting at 1 site in Greece. Open to participants aged 0 Days to 24 Months, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-13.
Sponsored by National and Kapodistrian University of Athens · Observational
A prospective study will be conducted involving children under 2 years of age hospitalized for bronchiolitis during the period 2025-2026. Serum levels of 25-OH vitamin D (by chemiluminescence assay), VDR gene polymorphisms (through molecular techniques), and mitochondrial mass of T lymphocytes (by flow cytometry), will be determined in patients at the acute phase of bronchiolitis and in healthy controls. The children will be followed-up for 36 months, with systematic documentation of wheezing episodes and the prognostic value of the biomarkers mentioned above for the later development of recurrent wheezing will be assessed.
This study aims to explore the associations between vitamin D levels, VDR polymorphisms and T-cell mitochondrial mass with bronchiolitis severity and the subsequent risk of wheezing episodes. It is hoped that predictive biomarkers for wheezing risk following bronchiolitis and potential therapeutic targets will be identified.
Bronchiolitis is one of the most common causes of hospitalization in infants, with a significant proportion of these children developing recurrent wheezing episodes or asthma later in life. The risk of wheezing appears to be influenced by the immune response, although the underlying mechanisms remain unclear.
Vitamin D and its receptor (VDR) regulate both T-cell function and mitochondrial activity, which is essential for T-cell activation. Mitochondrial mass (MM) is emerging as a novel marker of mitochondrial activity and immune cell metabolic dynamics. However, the study of MM in children with bronchiolitis is currently limited.
A prospective study will be conducted involving children under 2 years of age hospitalized for bronchiolitis during the period 2025-2026. Serum levels of 25-OH vitamin D (by chemiluminescence assay), VDR gene polymorphisms (through molecular techniques), and mitochondrial mass of T lymphocytes (by flow cytometry), will be determined in patients at the acute phase of bronchiolitis and in healthy controls. The children will be followed-up for 36 months, with systematic documentation of wheezing episodes and the prognostic value of the biomarkers mentioned above for the later development of recurrent wheezing will be assessed.
This study aims to explore the associations between vitamin D levels, VDR polymorphisms and T-cell mitochondrial mass with bronchiolitis severity and the subsequent risk of wheezing episodes. It is hoped that predictive biomarkers for wheezing risk following bronchiolitis and potential therapeutic targets will be identified.
Methods Study design: This is a prospective, non-interventional study that will be conducted at the "Aghia Sofia" General Children's Hospital.
Study Population: The study will include children under 2 years of age who are diagnosed with bronchiolitis and hospitalized to the Second Pediatric Department and the Neonatal Unit of the 1st Pediatric Department of the National and Kapodistrian University of Athens at "Aghia Sofia" Children's Hospital. Diagnosis will be established according to the 2021 NICE criteria for bronchiolitis.
The control group will consist of healthy children without bronchiolitis, matched to patients for gestational age, chronological age, sex, in a 1:4 control-to-case ratio. Controls will be recruited during the same period as the patients to ensure comparability of the two groups with respect to seasonality, which is known to affect serum vitamin D levels.
Study Duration: The study will be conducted from October 2025 to September 2028 (3 years).
Data Collection and Processing: Prior to data collection, parents will be informed for the purposes of the study, and written consent will be obtained. The parental consent form, covering both the purpose of the study and patient data management, will follow the standard WHO consent template and comply with current data protection regulations. At admission, a blood sample will be collected for routine laboratory tests (complete blood count, CRP, blood gases, and a serum biochemical profile including calcium, phosphorus, and alkaline phosphatase), as well as determination of serum 25-OH vitamin D levels, vitamin D receptor (VDR) polymorphisms, and the mitochondrial mass of T-lymphocytes. The etiology of bronchiolitis (RSV or non-RSV) will also be determined by viral detection in nasopharyngeal secretions.
In the control group, mitochondrial mass of T-lymphocytes, serum vitamin D levels, and VDR polymorphisms will also be assessed, along with routine laboratory tests.
Clinical and laboratory data of children with confirmed bronchiolitis and controls will be recorded in a dedicated SPSS database. Baseline information will include demographic characteristics, personal and family medical history, and known risk factors for bronchiolitis or severe disease.
A clinical examination will be performed, and bronchiolitis severity will be assessed using the Modified Tal Score (MTS). During hospitalization, disease progression will be recorded, including length of hospitalization, admission to NICU/PICU, blood gas parameters (pO₂, pCO₂, pH, HCO₃-), oxygen supplementation/FiO₂, ventilation type, pharmacological management, complications, and mortality. In cases of clinical deterioration, the timing and corresponding MTS will be recorded as an indicator of severity of the disease.
After discharge, children will be followed up until 3 years of age, with documentation of recurrent wheezing episodes, defined as ≥ two or more wheezing episodes during the first three years of life.
Laboratory Methods:
Serum 25-OH vitamin D levels will be measured using chemiluminescence immunoassay (CLIA), a CDC-approved method.
VDR gene polymorphisms will be determined using PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphism). DNA will be isolated from peripheral blood. Using specific primers for VDR gene amplification, the polymorphisms of interest (FokI, BsmI, ApaI, and TaqI) will be identified. PCR products will undergo digestion with restriction endonucleases, and the resulting fragments will be analyzed by electrophoresis, enabling allele differentiation based on fragment length.
Mitochondrial mass of T-lymphocytes will be assessed by flow cytometry using fluorescent dyes that selectively bind to mitochondria. Peripheral blood T-lymphocytes will be isolated, incubated with the mitochondrial-specific fluorescent dye (reflecting total mitochondrial mass), and simultaneously stained with surface antibodies to identify T-cell subpopulations (CD4⁺, CD8⁺, CD14⁺). After washing and fixation, samples will be analyzed by flow cytometry, with fluorescence intensity reflecting relative mitochondrial mass.
Sample Size At least 100 samples from our population will be further analyzed. Statistical Analysis A descriptive analysis of the data will initially be performed. Subsequently, group comparisons will be conducted, and potential associations among variables of interest will be explored using univariate and multivariate analyses. Statistical analysis will be carried out with the Statistical Product and Service Solutions (SPSS) software. Τhe flow cytometry results will be analyzed using the Kaluza C Cytometry Analysis Software .
Consent and Ethics The study has been approved by the Ethics Committee of "Aghia Sophia" Children's Hospital (protocol number: 17253-09/07/2025). An informational leaflet will be provided to the participants' guardians, and written informed consent will be obtained prior to inclusion in the study. Clinical and epidemiological data will be used exclusively for research purposes. Patient information will remain strictly anonymous and all applicable personal data protection regulations will be fully applied.
Objectives The main research question is whether vitamin D levels and VDR polymorphisms are correlated with the mitochondrial mass of T-lymphocytes in infants with bronchiolitis, and whether they influence the risk of developing recurrent wheezing in later childhood.
The study 's additional aims are:
189 studies on the registry are indexed under Respiratory Sounds; 41 are open to participants now.
This study's planned enrollment of 130 is above the median of 109 across 82 observational studies indexed under Respiratory Sounds.
Browse Respiratory Sounds studies →National and Kapodistrian University of Athens is the lead sponsor of 176 studies on the registry; 54 are open to participants now.
Counted across the registry records on this site, refreshed daily.
The study will include children under 2 years of age who are diagnosed with bronchiolitis and hospitalized to the Second Pediatric Department and the Neonatal Unit of the 1st Pediatric Department of the National and Kapodistrian University of Athens at "Aghia Sofia" Children's Hospital. Diagnosis will be established according to the 2021 NICE criteria for bronchiolitis.
The control group will consist of healthy children without bronchiolitis, matched to patients for gestational age, chronological age, and sex, at a 1:4 ratio. Controls will be recruited during the same period as the patients to ensure comparability of the two groups with respect to seasonality, which is known to affect serum vitamin D levels.
Inclusion Criteria:
The study will include children under 2 years of age who are diagnosed with bronchiolitis and hospitalized to the Second Pediatric Department and the Neonatal Unit of the 1st Pediatric Department of the National and Kapodistrian University of Athens at "Aghia Sofia" Children's Hospital. Diagnosis will be established according to the 2021 NICE criteria for bronchiolitis.
The control group will consist of healthy children without bronchiolitis, matched to patients for gestational age, chronological age, and sex, at a 1:4 ratio. Controls will be recruited during the same period as the patients to ensure comparability of the two groups with respect to seasonality, which is known to affect serum vitamin D levels.
Εxclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Infants \<24months who were hospitalized with bronchiolitis during the season 2025-2026
Other: No Intervention: Observational Cohort
The control group will consist of otherwise healthy infants \<24 months of age who were hospitalized during the same time period for non-infectious causes. Children will be excluded from the control group if they have any underlying bone, metabolic, or endocrine disorders, or if they are hospitalized for any condition known to increase oxidative stress or alter the immune response.
Other: No Intervention: Observational Cohort
No intervetion
Mitochondrial Mass in T-lymphocytes
The mitochondrial mass of T-lymphocytes will be measured by flow cytometry, utilizing peripheral blood samples obtained during routine complete blood count (CBC) draws. These measurements will be compared between children with bronchiolitis and healthy controls.
Time frame: Within 12 hours upon childs admission
25-OH vitamin D levels
Peripheral blood samples will be collected to measure serum levels of 25-hydroxyvitamin D \[25(OH)D\]. Statistical comparisons of these levels will be conducted both within the bronchiolitis patient group (to assess potential correlations with disease severity) and between the overall patient cohort and the healthy control group.
Time frame: 1-3 days upon admission
Vitamin D Receptor Polymorphisms
Peripheral blood samples will be utilized to assess Vitamin D Receptor (VDR) expression levels in T-lymphocytes via flow cytometry. Comparisons of VDR expression will be performed among children hospitalized with bronchiolitis, followed by a comparative analysis between the patients and healthy controls.
Time frame: During the 2025-2026 season (blood samples will be refrigerated and analysed later)
Plan to share: No — The ethical approval granted by the Institutional Review Board (IRB) does not authorize the public sharing of individual participant data, even in an anonymized format, in order to protect patient privacy.
No publications or documents are linked to this record.
Started Dec 2025 (actual). Primary completion is estimated for Dec 2028, 36 months after the start.
Of 38 observational studies under Respiratory Sounds, half reached primary completion within 45 months of starting (the median), counting those still running; a quarter within 21 and three quarters within 97. This study's planned 36 months is below that.
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This study is active, not recruiting, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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