Is Daily Home Spirometry an Effective Tool for Detecting Disease Progression in IPF?
Following a diagnosis of idiopathic pulmonary fibrosis (IPF), prognosis is generally poor, with a median survival of 3-5 years.1 Furthermore, the variable clinical course associated with disease progression makes patient management a challenge for health care professionals (HCPs).2 One of the best measures of IPF progression is change in forced vital capacity (FVC);3 however, FVC measurements are only done periodically in outpatient settings. Coupled with the variable and unpredictable course of IPF,4 traditional intermittent FVC measurements fail to capture the true breadth of IPF progression.2 However, with the recent miniaturization and falling cost of medical devices, home spirometry has already been adopted for monitoring of acute rejection in lung transplant recipients5 and, as such, may be useful to monitor IPF progression and early detection of acute exacerbations of IPF.2 To this end, the aim of this study was to assess the feasibility, reliability, and potential advantages of daily domiciliary measurements of FVC to provide a more granular picture of IPF progression and better manage patient care.2
What They Did
Study participants (N=50) were given a portable hand-held Micro spirometer (CareFusion), which fully conforms to current American Thoracic Society and European Respiratory Society standards. Subjects were given a dedicated 60-minute training session, with a refresher course after approximately 1 month. Participants were asked to record their single daily spirometry readings at roughly the same time each day in a dedicated diary. The patient-recorded FVC values were compared to typical clinical assessments that occurred at 3-month intervals, as well as lung function testing that occurred at 6 and 12 months during the study. The correlation between change in FVC and subsequent patient survival was analyzed using Cox proportional hazards regression for all values from baseline to 28 days, 3 months, 6 months, and 12 months. Rate of change in FVC was assessed categorically using thresholds of 5% and 10% declines from baseline.
What They Found
As corroborated by current literature, a 12-month rate of decline in FVC of ≥10% was strongly predictive of outcome (Fig. 1). Similarly, rate of change from baseline to 6 months was predictive of outcome when thresholds of 5% and 10% declines in FVC were applied. The authors also found that rate of decline of FVC at 3 months, when dichotomized at a 5% threshold, was the strongest predictor of subsequent outcome. Rate of change from baseline to day 28 failed to provide any prognostic value. Utilizing receiver operating characteristic (ROC) analysis, it was shown that 3-month change in FVC was strongly predictive of disease progression (area under curve [AUC] = 0.796, P<.001). Moreover, a >5% change at 3 months showed a specificity and selectivity of 90.5% and 62.1%, respectively, for predicting patients likely to have experienced disease progression at 12 months. Importantly, these data are in agreement with previously reported disease paradigms, with the majority of patients showing near-linear declines in FVC over time, and smaller groups of patients experiencing extremely rapid disease progression or acute exacerbations.4,6
What It Means
Daily domiciliary FVC assessments correlate well with hospital-based measurements; further, they were shown to be highly predictive of IPF progression and outcome and more sensitive than traditional, periodic, hospital-based measurements. This is important, as the majority of patients with IPF experience near-linear declines in FVC over time, allowing for a more granular picture of disease progression through the use of daily domiciliary spirometry. Home spirometry also has the potential to personalize patient care by allowing for the early identification and treatment of IPF-related complications, such as acute exacerbations of IPF. This is significant as these events are indicative of IPF progression and represent an increased risk of mortality.3
Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/27089018
- Collard HR, Moore BB, Flaherty KR, et al. Acute exacerbations of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. 2007;176:636-643.
- Russell AM, Adamali H, Molyneaux PL, et al. Daily home spirometry: An effective tool for detecting progression in idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. 2016.
- Reichmann WM, Yu YF, Macaulay D, Wu EQ, Nathan SD. Change in forced vital capacity and associated subsequent outcomes in patients with newly diagnosed idiopathic pulmonary fibrosis. BMC Pulm Med. 2015;15:167-180.
- Ley B, Collard HR, King TE Jr. Clinical course and prediction of survival in idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. 2011;183:431-440.
- Belloli EA, Wang X, Murray S, et al. Longitudinal forced vital capacity monitoring as a prognostic adjunct after lung transplantation. Am J Respir Crit Care Med. 2015;192:209-218.
- Martinez FJ, Safrin S, Weycker D, et al. The clinical course of patients with idiopathic pulmonary fibrosis. Ann Intern Med. 2005;142:963-967.