Progression of the Radiologic Severity Index predicts mortality in patients with parainfluenza virus-associated lower respiratory infections

<div><p>Background</p><p>Radiologic severity may predict adverse outcomes after lower respiratory tract infection (LRI). However, few studies have quantified radiologic severity of LRIs. We sought to evaluate whether a semi-quantitative scoring tool, the Radiologic Severity Index (RSI), predicted mortality after parainfluenza virus (PIV)-associated LRI.</p><p>Methods</p><p>We conducted a retrospective review of consecutively-enrolled adult patients with hematologic malignancy or hematopoietic stem cell transplantation and with PIV detected in nasal wash who subsequently developed radiologically-confirmed LRI. We measured RSI (range 0–72) in each chest radiograph during the first 30 days after LRI diagnosis. We used extended Cox proportional hazards models to identify factors associated with mortality after onset of LRI with all-cause mortality as our failure event.</p><p>Results</p><p>After adjustment for patient characteristics, each 1-point increase in RSI was associated with an increased hazard of death (HR 1.13, 95% confidence interval [CI] 1.05–1.21, p = 0.0008). Baseline RSI was not predictive of death, but both peak RSI and the change from baseline to peak RSI (delta-RSI) predicted mortality (odds ratio for mortality, peak: 1.11 [95%CI 1.04–1.18], delta-RSI: 1.14 [95%CI 1.06–1.22]). A delta-RSI of ≥19.5 was 89% sensitive and 91% specific in predicting 30-day mortality.</p><p>Conclusions</p><p>We conclude that the RSI offers precise, informative and reliable assessments of LRI severity. Progression of RSI predicts 30-day mortality after LRI, but baseline RSI does not. Our results were derived from a cohort of patients with PIV-associated LRI, but can be applied in validated in other populations of patients with LRI.</p></div

Characteristics of patients with hematopoietic stem cell transplants.

<p>Characteristics of patients with hematopoietic stem cell transplants.</p

Univariate logistic regression models for the prediction of 30-day mortality with baseline RSI, peak RSI and delta-RSI with any RSI score.

<p>Univariate logistic regression models for the prediction of 30-day mortality with baseline RSI, peak RSI and delta-RSI with any RSI score.</p

Trends in mean Radiologic Severity Index (RSI) scores over time in non-survivors (A) and survivors (B).

<p>(A) Trends in mean RSI scores are shown for patients who died within 14 days (solid circles, n = 4), patients who died between days 15 and 28 (solid squares, n = 5), and patients who died after day 28 (solid triangles, n = 2). (B) Trends in mean RSI scores are shown for survivors.</p

Scoring algorithm for the Radiologic Severity Index.

<p>Scoring algorithm for the Radiologic Severity Index.</p

Univariate and multivariate cox regression models for the prediction of 30-day mortality.

<p>Univariate and multivariate cox regression models for the prediction of 30-day mortality.</p

Univariate logistic regression models for the prediction of 30-day mortality with baseline RSI, peak RSI and delta-RSI with RSI-CXR scores.

<p>Univariate logistic regression models for the prediction of 30-day mortality with baseline RSI, peak RSI and delta-RSI with RSI-CXR scores.</p

Representative images of RSI scoring for CXR and CT images.

<p>RSI scores are labelled within each panel. Panels (A)-(C) show CXR images from an individual patient in order of increasing severity. Panels (D)-(F) show CT images from a different individual patient in order of increasing severity.</p

Bland-Altman plots for agreement between expert radiologists.

<p>Bland-Altman plots for agreement between expert radiologists in (A) RSI, (B) RSI scores restricted to computed tomography (CT) only (RSI-CT), and (C) RSI scores restricted to chest x-ray (CXR) measurements only (RSI-CXR). Upper and lower gray bars show 95% confidence intervals for upper and lower limits of agreement. Center gray bar shows 95% confidence intervals for bias. Solid line represents the slope of the bias (p = NS).</p

Agreement between readers for RSI scores.

<p>Agreement between readers for RSI scores.</p