Evaluation of Metabolomic Biomarkers in Pulmonary Fibrosis
Conditions: Pulmonary Fibrosis
Sponsor: University of Campania Luigi Vanvitelli

 
03/04/2023 
Evaluation of Metabolomic Biomarkers in Pulmonary Fibrosis 
 
Study Protocol and Statistical Plan  
 
We designed a single-center, prospective, cross-sectional investigation involving patients 
diagnosed with Pulmonary Fibrosis. Participants are recruited from the Interstitial Lung and 
Rare Diseases Outpatient Clinic at the Vanvitelli Respiratory Diseases Clinic, Monaldi 
Hospital, Naples, Italy. Patients were included if they met the following criteria: 1) Confirmed 
IPF diagnosis based on the 2018 ATS/ERS/JRS/ALAT guidelines [PMID: 30168753] within 
the past five years 2) diagnosis of other fibrotic interstitial lung disease different from IPF  3) 
age ≥ 40 years, 4) ability to provide informed consent. Exclusion criteria included: 1) a 
current diagnosis of asthma or chronic obstructive pulmonary disease (COPD), 2) an acute 
Pulmonary Fibrosis exacerbation within the past three months. Demographic and 
anthropometric data—including sex, smoking history, and comorbidities—are systematically 
recorded. All participants underogo pulmonary function testing, including spirometry, body 
plethysmography, and single-breath diffusing capacity of the lungs for carbon monoxide 
(DLCO), following the 2022 ATS/ERS guidelines [PMID: 34949706]. Tests are performed 
using the Vyntus BODY system (Vyaire Medical), and the following parameters were 
measured: FEV₁, FEV₁%, FVC, FVC%, FEV₁/FVC, TLC, TLC%, RV, RV%, DLCO, and 
DLCO% [PMID: 22743675, PMID: 28893868]. Additionally, arterial blood gas (ABG) analysis 
was conducted to assess pH, partial pressure of oxygen (pO₂), partial pressure of carbon 
dioxide (pCO₂), bicarbonate (HCO₃⁻), and lactate levels. Functional capacity is evaluated 
using the 6-minute walk test (6MWT), performed according to ATS guidelines [PMID: 
12091180]. The Gender-Age-Physiology (GAP) index was calculated to stratify IPF patients 
into three risk stages based on clinical (sex, age) and physiological (FVC, DLCO) 
parameters, providing an estimate of 1-, 2-, and 3-year mortality [PMID: 22586007]. To 
enhance prognostic accuracy, the Distance-Oxygen-Gender-Age-Physiology (DO-GAP) 
index was also determined by incorporating 6MWT distance and exertional hypoxemia 
[PMID: 37228268].  
 

 
 
Study Protocol Design  
Statistical plan  
Baseline population characteristics, comparing the control group and Pulmonary Fibrosis 
patients. In particular, the X² test or Spearman’s rank correlation (Rho) was applied to 
categorical variables according to their distribution, while the Wilcoxon-Mann-Whitney test 
was used for continuous variables to identify significant differences between the two groups 
(controls and PF). For univariate correlations, Pearson's or Spearman coefficient are used 
as appropriate. These statistical methods provide a comprehensive understanding of the 
clinical and biochemical differences between the two groups and the relationships among 
the fatty acids studied. Finally, we evaluated the diagnostic potential of significant FAs for 
IPF using Receiver Operating Characteristic (ROC) curves. A p-value < 0.05 was considered 
statistically significant.