Tjitske van Engelen

235 Low-dose-CT versus X-ray in patients suspected of pulmonary disease Text S2 Availability of prior imaging The ULDCT and CXR were read with prior imaging if available. In the ULDCT group in 35.2% (425/1208) of patients a prior CXR was used during reading and in 31.7% (383/1208) a prior chest-CT. In the CXR group in 62.4% (788/1210) of patients a prior CXR was used during reading and in 11.9% (144/1210) a prior chest-CT. In patients in the CXR group, a prior CXR was more often used for comparison compared to the ULDCT group. This is in accordance with regular clinical practice and related to the two dimensional projection technique of CXR and the lower number of images. ULDCT (N=830) .00 20.00 40.00 60.00 Physical component summary scale score (PCS) XCR (N=776) Figure S2 The distribution of the Physical component summary scale (PCS) scores. ULDCT: Ultra-low-dose chest computed tomography, CXR: Chest X-ray ⚫ Mean PCS score: ULDCT: 37.0 (95% CI 36.2 to 37.8), CXR: 35.9 (95% CI 35.2 to 36.7), difference 1.1 (95% lower CI: 0.003), histogram PCS in Supplementary Figure S2. Text S3 Imputation and sensitivity analyses Primary outcome: Sensitivity analyses Sensitivity analysis including the imputed 109 PCS scores of incomplete questionnaires using age and sex as variables (excluding four questionnaires in the ULDCT group and one questionnaire in the CXR group that were sent back completely blank) showed a result similar to the primary analysis: mean PCS score 36.9 in the ULDCT group (n=892) versus 35.9 in the CXR group (n=823), a difference of 1.0 (one-sided 95% lower CI: -0.06). Non-inferiority of ULDCT to CXR within the prespecified 1-point margin was therefore shown in the non-imputed and imputed data. Multivariable linear regression analysis on the non-imputed data with imaging modality as a predictor as well as baseline characteristics (age, gender, comorbidity, presenting symptoms, clinical question on radiology application form) resulted in a mean difference in PCS scores of 0.9 (one-sided 95% lower CI: -0.1), also indicating non-inferiority of ULDCT. 9

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