Causes of acute respiratory hospitalizations predict survival in fibrosing interstitial lung diseases

Our plain-English summary of Causes of acute respiratory hospitalizations predict survival in fibrosing interstitial lung diseases, by J. Salonen, H. Vähänikkilä, M. Purokivi, et al (PloS One, 2020).

The study

• Authors: J. Salonen, H. Vähänikkilä, M. Purokivi, R. Kaarteenaho
• Journal: PloS One
• Published: 2020;15(11):e0242860
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Acute exacerbation of ILD (AE-ILD) is a common reason for hospitalization; it is also associated with significant mortality. Less is known about the prognostic significance of other events causing acute, non-elective hospitalizations in ILD patients. ILD patients hospitalized due to acute respiratory worsening were collected from medical records. Reasons for respiratory deterioration were classified into AE-ILDs and other causes. Clinical features and survival data of idiopathic pulmonary fibrosis (IPF) and other types of ILDs were evaluated and compared. In all, 237 patients (138 with IPF and 99 with other ILD) fulfilled the inclusion criteria. Of the non-IPF ILD types, the most prevalent subgroups were connective tissue disease-associated ILD (n = 33) and asbestosis (n = 22). The most common cause for hospitalization was AE-ILD explaining 41% of hospitalizations. Lower respiratory tract infection (22%), subacute progression of ILD (12%) and cardiovascular causes (7.2%) were other common reasons for hospital treatment. Patients with a lower respiratory tract infection had a more favorable prognosis compared with patients with AE-ILD. AE-ILDs were less fatal than cardiovascular or concurrent non-ILD-related causes for hospitalizations in non-IPF patients. High Gender-Age-Physiology (GAP) index was a marker for shortened survival and earlier AE-ILDs in all patients. IPF patients had a significantly shorter overall and post-hospitalization survival time compared with other ILDs. Most respiratory hospitalizations in ILD patients were related to causes other than AE-ILD, which highlights the importance of accurate differential diagnosis in order to target the appropriate treatment for each ILD patient.

In plain English

This retrospective study used medical records from two Finnish hospitals. It covered 237 patients with fibrosing interstitial lung disease (ILD) who were admitted non-electively for acute respiratory symptoms between 2008 and 2017. Of these, 138 had idiopathic pulmonary fibrosis (IPF) and 99 had other ILDs, including 22 men with asbestosis and 2 patients with asbestosis plus rheumatoid arthritis. During follow-up, 10 of 22 asbestosis patients (45%) and 1 of 2 with asbestosis plus rheumatoid arthritis had an acute exacerbation of ILD; separate asbestosis survival results were not reported. Acute exacerbation caused 96 (41%) of first hospitalizations, lower respiratory tract infection 22%, and cardiovascular causes 7.2%. Compared with acute exacerbation, infection was associated with longer survival after hospitalization in all patients (hazard ratio 0.64, 95% CI 0.44 to 0.92). In non-IPF patients, cardiovascular and multifactorial causes were associated with shorter survival than acute exacerbation. Median survival from diagnosis was 3.5 years in IPF and 7.8 years in other ILDs. Higher Gender-Age-Physiology (GAP) stage was associated with earlier death and exacerbation. The authors concluded that clinicians should be aware of causes other than acute exacerbation, some possibly more serious.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective study based on medical records
• Who was studied: 237 patients with fibrosing ILD (138 with IPF, 99 with other ILD), all non-electively hospitalized for acute respiratory symptoms at Oulu University Hospital or Oulaskangas Hospital, Finland, from 1 January 2008 to 31 December 2017. Non-IPF types included connective tissue disease-associated ILD (33), asbestosis (22, all male) and asbestosis with rheumatoid arthritis (2).
• Exposure: Asbestos exposure was not measured, and no fiber types or doses are given. The factor compared was the cause of the first non-elective respiratory hospitalization. Asbestosis cases were identified through ICD-10 diagnosis codes, among them J61.
• Main results:
  • Acute exacerbation of ILD caused 96 (41%) of the 237 first hospitalizations, with no statistically significant difference between IPF and non-IPF patients.
  • Lower respiratory tract infection (22%) and cardiovascular causes (7.2%) were the most common single non-ILD-related causes of hospitalization.
  • Subacute ILD progression caused hospitalization more often in IPF patients (23 of 138, 17%) than in non-IPF patients (5 of 99, 5.1%), p = 0.006.
  • Survival after hospitalization was longer for patients hospitalized with lower respiratory tract infection than for those with acute exacerbation. Hazard ratios: all patients 0.64 (95% CI 0.44 to 0.92, p = 0.017); IPF 0.58 (0.36 to 0.92, p = 0.021); non-IPF 0.70 (0.37 to 1.32, p = 0.270, not statistically significant).
  • In non-IPF patients, survival after hospitalization was shorter than after acute exacerbation for cardiovascular causes (HR 3.29, 95% CI 1.36 to 7.94, p = 0.008) and for multifactorial causes (HR 3.08, 95% CI 1.42 to 6.67, p = 0.004).
  • Median survival from diagnosis was 3.5 years in IPF patients and 7.8 years in non-IPF patients (p less than 0.001).
  • Median survival after hospitalization was 1.1 years in IPF patients and 1.9 years in non-IPF patients (p = 0.001).
  • Hospital mortality was 11%, with no statistically significant difference between IPF and non-IPF patients.
  • In all patients, a higher GAP stage at diagnosis was associated with shorter survival and with earlier acute exacerbation. For GAP stage III compared with stage I, the HR for death was 4.45 (95% CI 2.80 to 7.07) and the HR for acute exacerbation was 2.81 (1.47 to 5.38).
  • Of the 22 asbestosis patients (all male), 10 (45%) had an acute exacerbation of ILD during follow-up. No separate survival analysis was given for asbestosis.
  • Of the 2 patients with asbestosis plus rheumatoid arthritis (both male), 1 (50%) had an acute exacerbation of ILD during follow-up.
• The authors' conclusion: The authors concluded that although acute exacerbation was the most common single cause, most hospitalizations had other causes. They said clinicians should be aware of these other possible causes in ILD patients with acute respiratory worsening, and that some of them may be even more serious than an exacerbation.
• Limitations the authors state:
  • Some patient data were missing, and clinicians may have used ICD-10 codes incorrectly, which may have excluded a few cases.
  • A radiologist did not re-evaluate the HRCT scans specifically for this study.
  • Few patients had each individual non-IPF ILD subtype.

Topics

Medical terms in this study, explained in our Lexicon: Interstitial Lung Disease, Idiopathic, Pulmonary Fibrosis, Prognosis, Differential Diagnosis.

Related studies

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• Possible value of antifibrotic drugs in patients with progressive fibrosing non-IPF interstitial lung diseases — S.E. Torrisi, N. Kahn, et al. (2019)
• Validation of the Brazilian Portuguese version of the University of California San Diego Shortness of Breath Questionnaire in patients with interstitial lung disease — H. Silva, L.C. Mantoani, et al. (2021)
• Comprehensive characterisation of individuals with fibrotic interstitial lung disease: baseline insights from the INJUSTIS study — F. Khan, I. Stewart, et al. (2026)
• Differential diagnosis of usual interstitial pneumonia: when is it truly idiopathic? — W.A. Wuyts, A. Cavazza, et al. (2014)
• Year in review 2011: acute lung injury, interstitial lung diseases, physiology, sleep and lung cancer — K. Takahashi, N.D. Eves, et al. (2012)

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