Chest
Volume 158, Issue 2, August 2020, Pages 620-629
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Diffuse Lung Disease: Original Research
Derivation and Validation of a Diagnostic Prediction Tool for Interstitial Lung Disease

Preliminary data for this study were presented in abstract form at the International Colloquium on Lung and Airway Fibrosis, October 13-17, 2018, Pacific Grove, CA, and the 2019 American Thoracic Society International Conference, May 17-22, 2019, Dallas, TX.
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Background

Interstitial lung disease (ILD) results in high morbidity and health-care utilization. Diagnostic delays remain common and often occur in nonpulmonology settings. Screening for ILD in these settings has the potential to reduce diagnostic delays and improve patient outcomes.

Research Question

This study sought to determine whether a pulmonary function test (PFT)-derived diagnostic prediction tool (ILD-Screen) could accurately identify incident ILD cases in patients undergoing PFT in nonpulmonology settings.

Study Design and Methods

Clinical and physiologic PFT variables predictive of ILD were identified by using iterative multivariable logistic regression models. ILD status was determined by using a multi-reader approach. An ILD-Screen score was generated by using final regression model coefficients, with a score ≥ 8 considered positive. ILD-Screen test performance was validated in an independent external cohort and applied prospectively to PFTs over 1 year to identify incident ILD cases at our institution.

Results

Variables comprising the ILD-Screen were age, height, total lung capacity, FEV1, diffusion capacity, and PFT indication. The ILD-Screen showed consistent test performance across cohorts, with a sensitivity of 0.79 and a specificity of 0.83 when applied prospectively. A positive ILD-Screen strongly predicted ILD (OR, 18.6; 95% CI, 9.4-36.9) and outperformed common ILD clinical features, including cough, dyspnea, lung crackles, and restrictive lung physiology. Prospective ILD-Screen application resulted in a higher proportion of patients undergoing chest CT imaging compared with a historical control cohort (74% vs 56%, respectively; P = .003), with a significantly shorter median time to chest CT imaging (5.6 vs 21.1 months; P < .001).

Interpretation

The ILD-Screen showed good test performance in predicting ILD across diverse geographic settings and when applied prospectively. Systematic ILD-Screen application has the potential to reduce diagnostic delays and facilitate earlier intervention in patients with ILD.

Section snippets

Patients and Methods

This investigation was performed at the University of California at Davis and the Centre Hospitalier de l’Université de Montréal (CHUM). It was approved by the institutional review board at each center, which provided waivers of consent (UC-Davis protocol #928979 and CHUM protocol #2019-7786).

ILD-Screen Derivation

Of 1,271 patients undergoing paired PFT and chest CT imaging over the derivation period, 212 (16.7%) had evidence of ILD. Interobserver agreement for ILD presence on chest CT imaging was good (κ = 0.79). Compared vs those without ILD, case subjects were older, with a higher predominance of male subjects and lower TLC, FVC, and Dlco (Table 1). ILD was observed in a higher number of patients referred for a pulmonary indication compared with a nonpulmonary indication.

Variables selected for the

Discussion

In the current investigation, we developed the ILD-Screen, a diagnostic prediction tool for ILD derived from variables collected on PFTs. Prospective application of the ILD-Screen identified a large number of incident ILD cases, including all cases with pulmonary fibrosis and nearly all patients with IPF, CTD-ILD, and U-ILD. The ILD-Screen showed consistent test performance across two geographically diverse North American cohorts and when applied prospectively, thus suggesting good

Conclusions

The current study showed that the ILD-Screen is a more reliable predictor of ILD than hallmark clinical and physiologic features of ILD among patients undergoing PFT for diverse indications and across various care settings. This tool represents a promising modality to begin identifying at-risk patients who should be referred for HRCT imaging, as such an intervention has the potential to reduce diagnostic delays, facilitate earlier intervention, and improve patient outcomes.

Acknowledgments

Author contributions: J. M. O. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. J. V. P., S. A., A.-C. M.-P., D. P., J. G., N. B., A. K., E. L., E. F., C. M., and S. C. were responsible for clinical/physiologic data acquisition. A. K., J. C., M. K., and J. M. O. were responsible for chest CT data acquisition. J. V. P., J. M., M. K., and J. M. O. designed the study. J. M. O. analyzed the data. J. V. P.,

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    FUNDING/SUPPORT: This study was funded by the National Heart, Lung, and Blood Institute [K23HL138190].

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