Unsupervised home spirometryversussupervised clinic spirometry for respiratory disease: a systematic methodology review and meta-analysis

Background: The number of patients completing unsupervised home spirometry has recently increased due to more widely available portable technology and the COVID-19 pandemic, despite a lack of solid evidence to support it. This systematic methodology review and meta-analysis explores quantitative differences in unsupervised spirometry compared with spirometry completed under professional supervision. Methods: We searched four databases to find studies that directly compared unsupervised home spirometry with supervised clinic spirometry using a quantitative comparison ( e.g. Bland–Altman). There were no restrictions on clinical condition. The primary outcome was measurement differences in common lung function parameters (forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC)), which were pooled to calculate overall mean differences with associated limits of agreement (LoA) and confidence intervals (CI). We used the I 2 statistic to assess heterogeneity, the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool to assess risk of bias and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess evidence certainty for the meta-analyses. The review has been registered with PROSPERO (CRD42021272816). Results: 3607 records were identified and screened, with 155 full texts assessed for eligibility. We included 28 studies that quantitatively compared spirometry measurements, 17 of which reported a Bland–Altman analysis for FEV 1 and FVC. Overall, unsupervised spirometry produced lower values than supervised spirometry for both FEV 1 with wide variability (mean difference −107 mL; LoA= −509, 296; I 2 =95.8%; p<0.001; very low certainty) and FVC (mean difference −184 mL, LoA= −1028, 660; I 2 =96%; p<0.001; very low certainty). Conclusions: Analysis under the conditions of the included studies indicated that unsupervised spirometry is not interchangeable with supervised spirometry for individual patients owing to variability and underestimation.