Abstract
Detection of idiopathic interstitial pneumonias (IIPs) on chest X-ray is difficult for non-specialist physicians, especially in patients with mild IIPs. The current study aimed to evaluate the usefulness of a simple method for detecting IIPs by measuring vertical lung length (VLL) in chest X-rays to quantify decreased lung volume. A total of 280 consecutive patients with IIPs were randomly allocated to exploratory and validation cohorts, and 140 controls were selected for each cohort by propensity score-matching. Upper (uVLL; from apex to tracheal carina), lower (lVLL; from carina to costophrenic angle), and total VLL (tVLL; from apex to costophrenic angle), and the l/uVLL ratio were measured on chest X-rays. Patients in the exploratory cohort had significantly decreased uVLL, lVLL, tVLL, and l/uVLL ratio compared with controls (all p < 0.001). Receiver operating characteristic curve analyses demonstrated that lVLL (area under the curve [AUC] 0.86, sensitivity 0.65, specificity 0.92), tVLL (AUC 0.83, sensitivity 0.75, specificity 0.80), and l/uVLL ratio (AUC 0.80, sensitivity 0.72, specificity 0.79) had high diagnostic accuracies for IIPs. These results were reproduced in the validation cohort. IIP patients thus have decreased VLLs, and measurements of VLL may thus aid the accurate detection of IIPs.
Highlights
Detection of idiopathic interstitial pneumonias (IIPs) on chest X-ray is difficult for non-specialist physicians, especially in patients with mild IIPs
All of the patients with IIPs had a reticular pattern on chest computed tomography (CT) images, and 70.4% and 94.3% had honeycombing and ground-glass opacity (GGO), respectively (Table 2)
After adjusting for age, sex, body mass index (BMI), %predicted forced vital capacity (FVC), %predicted FEV1, and %LAA in multivariate logistic regression analysis, there was no significant difference in uVLL, lVLL, total VLL (tVLL), or l/uVLL ratio between the idiopathic pulmonary fibrosis (IPF) and non-IPF groups (Supplementary Table 2)
Summary
Detection of idiopathic interstitial pneumonias (IIPs) on chest X-ray is difficult for non-specialist physicians, especially in patients with mild IIPs. The current study aimed to evaluate the usefulness of a simple method for detecting IIPs by measuring vertical lung length (VLL) in chest X-rays to quantify decreased lung volume. IIPs have become clinically important for non-pulmonologists in relation to the increasing use of biological, molecular targeted, and immune checkpoint-inhibitor agents as standard therapies in various fields of clinical medicine Despite their efficacy, these novel treatments have raised concern about the occurrence of drug-induced interstitial lung diseases as a life-threatening toxicity[8,9,10,11]. We aimed to develop a method to quantify decreased lung volume by measuring the vertical lung length (VLL) on chest X-ray, and to evaluate its usefulness for the detection of IIPs
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