Descriptive study of the role of ultrasound in the evaluation of patients with interstitial lung disease associated with autoimmune connective tissue disorders

Background and Aim: High-resolution computed tomography (HRCT) of the chest has been the conventionally accepted modality of radiological investigation utilized in the evaluation and management of interstitial lung diseases (ILDs). The aim of this study was to compare the utilization of lung ultrasound (LUS) as a radiological modality versus HRCT scan of the chest, in the diagnosis of cases of ILD in autoimmune connective tissue disease (AICTD) patients at a tertiary care center in Northern India. Methods: In this descriptive study, 42 consecutive diagnosed cases of AICTD with clinical risk of ILD were included, between July 2016 and March 2019, attending the rheumatology outpatient department of CH WC. They were assessed with lung ultrasonography and HRCT chest. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of LUS were estimated considering HRCT as the reference method. Results: Of these 42 patients, 30 (71.4%) had abnormal LUS findings. HRCT findings suggestive of ILD were seen in 31 (73.8%). Considering HRCT as gold standard, LUS resulted in 01 false-positive and 02 false-negative results. Sensitivity and specificity of LUS with respect to HRCT were 93.55% and 90.91%, respectively. Positive predictive value (PPV) and negative predictive value (NPV) of LUS were calculated at 89.38% and 94.51%, respectively. In 91.6% (11/12) patients with nonspecific interstitial pneumonitis pattern on HRCT, B-lines were found to be numerous and compact (<3 mm distance between B lines). On the other hand, compact B lines were seen in only 21.1% (4/19) cases showing HRCT patterns suggestive of usual interstitial pneumonitis (UIP)/likely UIP, with a significant difference between the two (P = 0.0002). Conclusions: LUS is as nearly sensitive and specific as HRCT chest in the detection of ILD and has the distinct advantage of being without radiation exposure.