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In The British journal of radiology

OBJECTIVE : The purpose was to evaluate reader variability between experienced and in-training radiologists of COVID-19 pneumonia severity on CXR, and to create a multi reader database suitable for AI development.

METHODS : In this study, CXRs from PCR positive COVID-19 patients were reviewed. Six experienced cardiothoracic radiologists and two residents classified each CXR according to severity. One radiologist performed the classification twice to assess intra observer variability. Severity classification was assessed using a four-class system: normal(0), mild, moderate, and severe. A median severity score (Rad Med) for each CXR was determined for the six radiologists for development of a multi reader database (XCOMS). Kendal Tau correlation and percentage of disagreement were calculated to assess variability.

RESULTS : A total of 397 patients (1208 CXRs) were included (mean age, 60 years SD ±1), 189 men). Inter observer variability between the radiologists ranges between 0.67-0.78. Compared to the Rad Med score, the radiologists show good correlation between 0.79-0.88. Residents show slightly lower inter observer agreement of 0.66 with each other and between 0.69-0.71 with experienced radiologists. Intra observer agreement was high with a correlation coefficient of 0.77. In 220 (18%), 707 (59%), 259 (21%) and 22 (2%) CXRs there was a 0, 1, two or three class-difference. In 594 (50%) CXRs the median scores of the residents and the radiologists were similar, in 578 (48%) and 36 (3%) CXRs there was a 1 and 2 class-difference.

CONCLUSION : Experienced and in-training radiologists demonstrate good inter and intra observer agreement in COVID-19 pneumonia severity classification. A higher percentage of disagreement was observed in moderate cases, which may affect training of AI algorithms.

ADVANCES IN KNOWLEDGE : Most AI algorithms are trained on data labeled by a single expert. This study shows that for COVID-19 X-ray severity classification there is significant variability and disagreement between radiologist and between residents.

van Assen Marly, Zandehshahvar Mohammadreza, Maleki Hossein, Kiarashi Yashar, Arleo Timothy, Stillman Arthur E, Filev Peter, Davarpanah Amir H, Berkowitz Eugene A, Tigges Stefan, Lee Scott J, Vey Brianna L, Adibi Ali, De Cecco Carlo Nicola