Here are some key points from a review in the Journal of Hospital Medicine:
What is the classification?
Categories are exposure related (eg hypersensitivity pneumonitis, drugs, occupational), connective tissue disease related, idiopathic and miscellaneous (including sarcoid, Langerhans cell histiocytosis, eosiniphilic pneumonia and vasculitis (including diffuse alveolar hemorrhage).
What labs should be ordered initially on a patient suspected for the first time to have ILD?
According to the review, ANA, RA, anti cyclic citrullinated peptide, CK and aldolase. (Aldolase may be elevated while the CK is normal in some cases of inflammatory myopathy). (I would wonder if synthetase antibody testing should be added to this list). After this round of testing, subsequent tests can be added based on initial results and the ensuing clinical course.
What imaging studies should initially be done?
CXR and HRCT according to the article, which also mentioned that if clinical conditions warrant, instead of just doing a HRCT, get a CT PA gram with simultaneous high resolution images of the lung parenchyma.
What about bronchoscopy?
This is not considered routine and what I get from the review is that the diagnostic confidence derived from HRCT and the anticipation of how the results might change treatment will influence this decision. Circumstances that might favor doing bronchoscopy include suspected acute eosinophilic pneumonia (AEP), suspected acute hypersensitivity pneumonitis, suspected sarcoid and suspected unusual infection.
When should antibiotics be given?
According to the review, onset or exacerbation of ILD can be difficult to distinguish from infection, so always at least consider them. (Given the all too often undifferentiated nature of the presentation in critically ill patients, I suspect the threshold would be low). The review did not comment on the specific type of coverage. However, many such patients are immunosuppressed, have had frequent hospitalizations, or are critically ill and those factors would guide antibiotic choices.
Should corticosteroids be used?
In cases of clinical deterioration or respiratory failure, which is the case with most patients who require hospitalization, yes. The etiology is often unknown, and it must be kept in mind that some etiologies are known to be highly steroid responsive, particularly AEP and COP. Recommendations also support the use of steroids for CTD related ILD, acute HP and drug induced ILD. IPF by comparison is poorly steroid responsive but current guidelines conditionally recommend their use.
Cautions that would apply include the ever present risk of unusual infection and the potential for steroids to increase the risk of renal crisis in patients with systemic sclerosis.
Lung transplantation is a consideration for certain non responding patients
Form the article:
In these cases, lung transplantation may be the only remaining treatment option. This is particularly true for patients presenting with IPF, and it is 1 of the most common indications for lung transplantation. Patients with respiratory failure and ILD should be evaluated early in the hospital course for transplantation or considered for transfer to a transplant center. General contraindications to transplant are age older than 70 years, underweight or elevated BMI (generally higher than 30), malignancy within the last 2 years (with the exception of cutaneous squamous and basal cell tumors), untreatable major organ dysfunction other than the lung, noncurable chronic extrapulmonary infection (chronic active viral hepatitis B, hepatitis C, human immunodeficiency virus), significant chest wall deformity, untreatable psychiatric or psychologic disease, substance addiction within the last 6 months, or lack of dependable social support.4
Another excellent review, free full text, is here. Though a couple of years old it is still relevant and has lots of pearls.