Assessing Lung Involvement in Paediatric Rheumatic Diseases: A Retrospective Evaluation of the Limitations of Spirometry.

Objective: Lung involvement in paediatric rheumatic diseases significantly impacts morbidity and mortality. High-resolution computed tomography (HRCT) is a sensitive diagnostic tool but raises concerns about radiation exposure. Spirometry, a non-invasive and accessible test, is often used to assess pulmonary function, but its accuracy in detecting lung disease in newly diagnosed pediatric rheumatic conditions remains uncertain. This study evaluates spirometry's reliability, using HRCT as the reference standard. Methods: Patients suspected of lung involvement due to respiratory symptoms or disease prevalence underwent HRCT and pulmonary assessment. A retrospective review of HRCT scans was conducted for 22 pediatric patients diagnosed with rheumatic disease (January 2021-December 2023), all of whom had pathological findings. HRCT was performed using a paired end-inspiratory and forced-expiratory protocol with 1-mm collimation. Radiological findings, including parenchymal opacities, ground-glass opacities, reticular patterns, honeycombing, parenchymal bands, bronchiectasis, peribronchial wall thickening, and air trapping, were assessed. Spirometric values-percent predicted Forced Expiratory Volume in 1 second (ppFEV1), Forced Vital Capacity (ppFVC), and FEV1/FVC ratio-were collected for patients with acceptable flow-volume curves. Results: Seventeen of 22 patients (77.3%) had technically acceptable spirometry. Compared to HRCT, spirometry demonstrated a sensitivity of 29.4%. Conclusion: Despite its excellent positive predictive value, spirometry's low sensitivity suggests it may miss early lung involvement in paediatric rheumatic diseases. HRCT remains the preferred diagnostic tool to ensure accurate detection and management, despite radiation concerns.