Baseline characteristics and comorbidities in the CAnadian REgistry for Pulmonary Fibrosis

Background

The CAnadian REgistry for Pulmonary Fibrosis (CARE-PF) is a multi-center, prospective registry designed to study the natural history of fibrotic interstitial lung disease (ILD) in adults. The aim of this cross-sectional sub-study was to describe the baseline characteristics, risk factors, and comorbidities of patients enrolled in CARE-PF to date.

Methods

Patients completed study questionnaires and clinical measurements at enrollment and each follow-up visit. Environmental exposures were assessed by patient self-report and comorbidities by the Charlson Comorbidity Index (CCI). Baseline characteristics, exposures, and comorbidities were described for the overall study population and for incident cases, and were compared across ILD subtypes.

Results

The full cohort included 1285 patients with ILD (961 incident cases (74.8%)). Diagnoses included connective tissue disease-associated ILD (33.3%), idiopathic pulmonary fibrosis (IPF) (24.7%), unclassifiable ILD (22.3%), chronic hypersensitivity pneumonitis (HP) (7.5%), sarcoidosis (3.2%), non-IPF idiopathic interstitial pneumonias (3.0%, including idiopathic nonspecific interstitial pneumonia (NSIP) in 0.9%), and other ILDs (6.0%). Patient-reported exposures were most frequent amongst chronic HP, but common across all ILD subtypes. The CCI was ≤2 in 81% of patients, with a narrow distribution and range of values.

Conclusions

CTD-ILD, IPF, and unclassifiable ILD made up 80% of ILD diagnoses at ILD referral centers in Canada, while idiopathic NSIP was rare when adhering to recommended diagnostic criteria. CCI had a very narrow distribution across our cohort suggesting it may be a poor discriminator in assessing the impact of comorbidities on patients with ILD.

Sex differences in physiological progression of idiopathic pulmonary fibrosis

In idiopathic pulmonary fibrosis, incidence is higher in males, and females may have better survival. The aim of the present study was to determine whether the rate of increase in desaturation during serial 6-min walk testing would be greater, and survival worse, for males versus females. Serial changes in the percentage of maximum desaturation area (DA) over 1 yr were estimated using mixed models in 215 patients. DA was defined as the total area above the curve created using desaturation percentage values observed during each minute of the 6-min walk test. Multivariate Cox regression assessed survival differences. Adjusting for baseline DA, 6-min walk distance, change in 6-min walk distance over time and smoking history, the percentage of maximum DA increased by an average of 2.83 and 1.37% per month for males and females, respectively. Females demonstrated better survival overall, which was more pronounced in patients who did not desaturate below 88% on ambulation at baseline and after additionally adjusting for 6-month relative changes in DA and forced vital capacity. These data suggest that differences in disease progression contribute to, but do not completely explain, better survival of females with idiopathic pulmonary fibrosis.

Glucose-dependent insulinotropic polypeptide stimulated insulin release from a tumor-derived beta-cell line (beta TC3)

The beta TC3 tumor cell line was examined for the presence of functional glucose-dependent insulinotropic polypeptide (GIP) receptors. Increasing amounts of natural porcine GIP decreased the binding of HPLC-purified [125I]GIP to beta TC3 cells in a concentration-dependent manner. Displacement of GIP was significant at concentrations as low as 500 pM, and the radioligand was fully displaced at 100 nM. GIP(1-30) produced a displacement of [125I]GIP comparable with that produced by GIP(1-42), and glucagon yielded 20% displacement at a concentration of 1 microM but was without effect at 100 mM. Incubation of beta TC3 cells in the presence of glucose concentrations of 2-20 mM yielded a concentration-dependent stimulation of immunoreactive insulin (IRI) release. GIP and glucagon-like peptide-I(7-36) amide (tGLP-I) at concentrations of 1 nM or greater significantly stimulated IRI release in the presence of 2 mM glucose. The threshold glucose concentration for GIP-stimulated IRI release from beta TC3 cells was 0.5 mM, and maximal potentiation of IRI release by GIP occurred at 5 mM glucose. Somatostatin significantly inhibited GIP-stimulated IRI release in the presence of 5 mM glucose. It is concluded that beta TC3 cells have functional GIP receptors and may provide a useful model for the study of IRI secretion at the cellular level.