IntroductionInterstitial lung disease (ILD) is a frequent manifestation of connective tissue disease (CTD) with substantial variability in prevalence and outcomes reported across CTD subtypes. This systematic review summarises the prevalence, risk factors and ILD patterns on chest computed tomography of CTD-ILD.MethodsA comprehensive search was performed in Medline and Embase to identify eligible studies. Meta-analyses were completed using a random effects model to determine the pooled prevalence of CTD-ILD and ILD patterns.Results11 582 unique citations were identified with 237 articles included. Pooled prevalence of ILD was 11% in rheumatoid arthritis (95% CI 7–15%), 47% in systemic sclerosis (44–50%), 41% in idiopathic inflammatory myositis (33–50%), 17% in primary Sjögren's syndrome (12–21%), 56% in mixed connective tissue disease (39–72%) and 6% in systemic lupus erythematosus (3–10%). Usual interstitial pneumonia was the most prevalent ILD pattern in rheumatoid arthritis (pooled prevalence of 46%), while nonspecific interstitial pneumonia was the most common ILD pattern in all other CTD subtypes (pooled prevalence range 27–76%). Across all CTDs with available data, positive serology and higher inflammatory markers were risk factors for development of ILD.DiscussionWe identified substantial variability in ILD across CTD subtypes suggesting that CTD-ILD is too heterogenous to be considered a single entity.

BackgroundThe prevalence of sensitization varies geographically based on multiple environmental factors including humidity. The aim of this study was to determine the prevalence of atopy in symptomatic adults. More importantly we aimed to obtain a regional statistic of sensitization to common allergens given Saskatchewan’s dry climate.MethodsOne thousand consecutive symptomatic adults were screened for atopy via skin prick test over 10 years (2006–2016) in the Division of Respirology. An atopic screen was performed with twenty common aeroallergens by a single investigator, Dr. D. Cockcroft. A positive test was considered to be a wheal ≥3 mm and markedly positive reactions ≥8 mm were also documented.ResultsThe prevalence of atopy by means of a positive skin test (≥3 mm) was 45.5%. The prevalence of one or more markedly positive reactions (≥8 mm) was 29.5% of the total population. The most frequent sensitization was to cat dander (58.2%), followed by mixed grass (32.1%), and birch (26.8%). Dust mite sensitization was 22.4% and mouse 6.2%. A positive epidemiology screen for cat/grass/mite would have incorporated 82.0% (n = 373) of subjects with positive skin tests. Those who failed the cat/grass/mite screen were mainly sensitized to trees (n = 34), molds (n = 22), weeds (n = 7), and animals (n = 8).ConclusionsThere is a high prevalence of cat sensitization in Saskatchewan, much higher than recorded in other centers internationally. This is likely due to a high proportion of cat ownership. The prevalence of mite sensitization is lower than those mentioned at other centres likely due to Saskatchewan’s dry climate. The significance of the rate of markedly positive reactions (≥8 mm wheal) when compared to humid areas with higher burden of mite is unknown. There is a low prevalence of roach also likely due to the dry climate and mouse sensitization was low but still identified as a significant indoor allergen. A cat/grass/mite screen may be useful with a 82.0% sensitivity.

Background and objective Inhalational exposures are a known cause of interstitial lung disease (ILD), but little is understood about their prevalence across ILD subtypes and their relationship with pulmonary function and survival. Methods Patients with fibrotic ILD were identified from the multicentre Canadian Registry for Pulmonary Fibrosis. Patients completed questionnaires regarding ILD‐related occupational and environmental exposures. The relationship between exposures and the outcomes of baseline age, gender, family history, pulmonary function and survival was analysed using linear and logistic regression models, linear mixed‐effect regression models and survival analysis using multivariable Cox proportional hazards along with the log‐rank test. Results There were 3820 patients included in this study, with 2385 (62%) having ILD‐related inhalational exposure. Exposed patients were younger, particularly in the idiopathic pulmonary fibrosis subgroup. Inhalational exposure was associated with male gender (adjusted OR 1.46, 95% CI 1.28–1.68, p < 0.001) and family history of pulmonary fibrosis (adjusted OR 1.73, 95% CI 1.40–2.15, p < 0.001). Patients with any inhalational exposure had improved transplant‐free survival (hazard ratio 0.81, 95% CI 0.71–0.92, p = 0.001); this effect persisted across diagnostic subtypes. The relationship between exposures and annual change in forced vital capacity varied by ILD subtype. Conclusion Patients with fibrotic ILD report high prevalence of inhalational exposures across ILD subtypes. These exposures were associated with younger age at diagnosis, male gender and family history of pulmonary fibrosis. Identification of an inhalational exposure was associated with a survival benefit. These findings suggest that inhaled exposures may impact clinical outcomes in patients with ILD, and future work should characterize the mechanisms underlying these relationships.

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Background and objective Rheumatoid arthritis (RA) is a frequent cause of interstitial lung disease (ILD); however, the impact of rheumatoid factor and anti‐citrullinated peptide antibody seropositivity in ILD without connective tissue disease (CTD) is unclear. We examined the association of seropositivity with ILD progression, mortality and response to immunosuppression in non‐CTD ILD. Methods A total of 1570 non‐CTD patients (with idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, interstitial pneumonia with autoimmune features or unclassifiable ILD) and 181 RA‐ILD patients were included from a prospective registry. Longitudinal forced vital capacity (FVC), transplant‐free survival and incidence of progressive fibrosing‐ILD (PF‐ILD) were compared between seronegative non‐CTD ILD (reference group), seropositive non‐CTD ILD and RA‐ILD using linear mixed‐effect and Cox proportional hazards models adjusted for age, sex, smoking pack‐years and baseline FVC. Interaction between seropositivity and immunosuppression on FVC decline was assessed in patients with ≥6 months of follow‐up before and after the treatment. Results Two hundred and seventeen (13.8%) patients with seropositive non‐CTD ILD had similar rates of FVC decline and transplant‐free survival compared to seronegative non‐CTD ILD, but more frequently met the criteria for PF‐ILD (hazard ratio [HR] = 1.35, p = 0.004). RA‐ILD had slower FVC decline (p = 0.03), less PF‐ILD (HR = 0.75, p = 0.03) and lower likelihood of lung transplant or death (HR = 0.66, p = 0.01) compared to seronegative non‐CTD ILD. No interaction was found between seropositivity and treatment on FVC decline in non‐CTD ILD. Conclusion Seropositivity in non‐CTD ILD was not associated with improved outcomes or treatment response, highlighting the importance of other disease features in determining prognosis and predicting response to immunosuppression.