·To explore the reliability and validity of Corona Virus Disease 2019 (COVID-19) Peritraumatic Distress Index (CPDI) in evaluating pandemic-related acute stress reaction.

·From 31 January 2020 to 29 February 2020, CPDI, Patient Health Questionnaire-9 (PHQ-9), General Anxiety Disorder-7 (GAD-7) and Self-reporting Questionnaire-20 (SRQ-20) were measured in 253 outpatients, their family members and medical staff of our hospital. At the same time, leveraging the Siuvo Intelligent Psychological Assessment Platform, we presented QR codes of the CPDI questionnaire online openly, accessible to the participants nationwide, and received a total of 75 867 valid responses. Cronbach's α coefficient was used to evaluate the internal consistency. The correlation between CPDI and PHQ-9, GAD-7 and SRQ-20 was used to test the criterion validity. Exploratory factor analysis was used to detect the structural validity and the cut-off score of the questionnaire to screen the psychological symptoms associated with COVID-19 was also detected.

·The Cronbach's α of the 15-item questionnaire was 0.932. The correlation coefficients between the 15-item CPDI and PHQ-9, GAD-7 and SRQ-20 were 0. 670, 0.699 and 0.711 respectively (all P=0.000). The exploratory factor analysis results contained 15 items and 4 factors, the factor load was 0.491-0.681, and the cumulative variance interpretation rate was 72.006%. In terms of cut-off score, it was identified as suspicious symptom by cut-off score of 10/11 points. The sensitivity and specificity were 0.822 and 0.811, respectively. The cut-off score to confirm the presence of symptoms was 14/15 points. The sensitivity and specificity were 0.815 and 0.824, respectively.

·The study indicates that CPDI is with good internal consistency reliability, criterion validity and structural validity.