Criteria for the classification of interstitial pneumonia with autoimmune features (IPAF) could be refined to improve the homogeneity of the patient population.

Although the current European Respiratory Society (ERS) and American Thoracic Society (ATS) criteria are only three years old, a recent comparison of four IPAF cohorts has revealed considerable differences between the patient groups.

Associate Professor Katerina Antoniou, a member of the 2015 ERS/ATS taskforce, told the ERS Congress that IPAF classification currently requires at least one feature from at least two domains – clinical, serologic and morphologic.

Suggested refinements include adding anti-neutrophil cytoplasmic antibodies (ANCA) and anti-Ku antibodies to the current list of specific circulating autoantibodies in the serologic domain.

An improvement in specificity could also be obtained by adding in cut-offs to pulmonary function testing and further clarifying the multi-compartment lung involvement in the morphologic domain.

Exclusion of patients with features extremely specific for connective tissue disease such as giant capillaries on nailfold videocapillaroscopy was also suggested.

Associate Professor Antoniou, a pulmonologist from the University of Crete, said currently patients with undifferentiated CTD-ILD frequently fulfil IPAF criteria.

Oesophageal dysmotility was another clinical feature which may be more specific for connective tissue disease and should be reconsidered in subsequent IPAF criteria iterations.

The comparison of IPAF cohorts also found rates of usual interstitial pneumonia (UIP) varied significantly from about 9% to 50%.

“Questions remain about whether UIP should be considered exclusionary for IPAF diagnosis,” she said.

Associate Professor Antoniou said active involvement of a rheumatologist in the multidisciplinary team was critical especially when lung involvement was subtle and in cases which may involve very early systemic sclerosis or myositis.

“Rheumatological assessment is important. We have to have very close collaboration with [rheumatologists] in these sub-populations in order to avoid delay of disease modifying treatment.”

She highlighted a recent study which showed rheumatological assessment reclassified a fifth of patients from IPF to connective tissue disease and could have prevented invasive procedures such as bronchoscopies and surgical biopsy.

“We think there should be more interaction between the pulmonologist and rheumatologist.”