On computed tomography (CT) scans, what has been described as a pattern that is “indeterminate for usual interstitial pneumonia” (iUIP) could be indicative of early idiopathic pulmonary fibrosis (IPF) in certain individuals, with disease progression possibly associated with higher levels of monocytes and neutrophils. These were among the results of a study recently published in the journal BMJ Open Respiratory Research.
A retrospective, single-center analysis was conducted among a lung fibrosis cohort of patients who had attended the Oxford Interstitial Lung Disease Service between 2013 and 2017. The researchers sought to assess the radiologic progression of iUIP and to examine those factors linked to progression to IPF, recognizing that the early identification and treatment of these patients might help to improve outcomes. All of the individuals evaluated in the lung fibrosis cohort had exhibited a CT pattern of “possible UIP” or “UIP,” based on 2011 guidelines. The radiologists’ reports for all thoracic CT scans available for these individuals (including initial CTs prior to 2013) through August 2019 were reanalyzed and cross-checked against reports from the interstitial lung disease (ILD) multidisciplinary team.
Patients with an iUIP CT pattern were then categorized as either “nonprogressive” or “progressive,” according to a comparison of their initial CT scan with their latest follow-up CT scan. “Nonprogressive” individuals exhibited no change in their CT scan with respect to extent of disease or pattern of disease, whereas those deemed “progressive” showed either a visual increase in the extent of their disease or progression of their CT pattern to “definite UIP” or “probable UIP” pattern.
Among a total of 230 individuals who attended the lung fibrosis lLD clinic with CT patterns of “probable UIP” “possible UIP” or “definite UIP,” 21% (41 of 230) of cases with an iUIP were identified. Of these 48 individuals, 32 had received at least 1 follow-up thoracic CT since the initial scan. Among the 16 patients with no follow-up CT scan, 13 were discharged after a mean of 2.1 years without a CT scan, as they were deemed to be clinically stable, and 3 were considered not to require a second CT scan clinically.
Of the 32 individuals with follow-up CT scans, 23 patients demonstrated progression. Among these 23 participants, 17 were diagnosed with IPF over a mean of 3.9 ± 1.9 years. Per Cox proportional hazard modeling, monocyte levels (hazard ratio [HR], 23; 95% CI, 1.6-340.0; P =.03) and neutrophil levels (HR, 1.8; 95% CI, 1.3-2.3; P <.001) obtained at the time of their initial CT scan were significantly linked to progression to IPF.
The investigators concluded that the findings from the current study imply that some patients who exhibit an iUIP CT pattern might actually be individuals with early IPF whose disease progression might be associated with higher levels of monocytes and neutrophils. Additional analyses are warranted, said the researchers, to validate the use of blood monocytes and neutrophils as biomarkers for patients with iUIP who are at higher risk for progression to IPF and all-cause mortality.
Achaiah A, Rathnapala A, Pereira A, et al. Monocyte and neutrophil levels are potentially linked to progression to IPF for patients with indeterminate UIP CT pattern. BMJ Open Respir Res. 2021;8(1):e000899. doi:10.1136/bmjresp-2021-000899