(203) Incidence of intussusception among children under 6 years of age in Ningbo, China, 2015-2021: a retrospective cohort study using electronic health records

Publication Number: 1195

Background: The estimation of intussusception incidence in Chinese children were contradictory among previous studies, and no study reported the incidence density of intussusception with a populational based cohort.

Objectives: To describe the epidemiologic characteristics of intussusception among children aged < 6 years in Ningbo City, monitoring its long-term trends before and after introduction of new rotavirus vaccine.

Methods: Setting: We conducted a retrospective cohort study of routine electronic health records from the Ningbo Regional Health Information Platform covering 7.9 million inhabitants. The study population was aged < 6 years，who had at least 180 days of continuous follow-up, and had at least one dose of vaccine from January 2015 to June 2021. Intussusception cases were identified by ICD-10 codes and Chinese terms of “changtao(肠套) ” from any of hospital discharge settings, including outpatient, emergence, inpatient, radiology and surgery. All potential cases adjudicated through chart review in line with international (Brighton Collaboration level 1) criteria. The episode was defined as any intussusception-related records within 48 hours.
Statistical analysis: Frequency comparisons between groups were performed using the chi-square test, and follow-up time comparisons were performed using K-W test. Confidence intervals for incidence density were calculated using the Clopper-Pearson method. Incidence density with 95% CI were stratified by age group, sex, region and calendar year. All statistical analyses were performed using SAS 9.4, and 𝑃 < 0.05 was considered to be statistically significant.

Results: A total of 1,302,937 infants with 3,765,767.35 person-years were included in the dynamic birth cohort and 3,183 cases of intussusception with 3,533 episodes were identified. The overall incidence rate of intussusception was 93.82 (95%CI: 90.75-96.96) per 100,000 person-years. The incidence density peaked in children aged 6-11 months (209.46/100,000 person-years), and then gradually decreased with age. The incidence rate was higher in male than female for the study period (118.25 versus 66.47, p < 0.05). There is no difference of intussusception incidence between the urban and rural area. From the calendar year of 2015 to 2021, overall trend of incidence had no significant changes. Intriguingly, the lowest incidence of 64.50 (95% CI 57.34–72.31) per 100,000 observed in year of 2020.

Conclusions: Incidence of intussusception among Chinese children in Ningbo city differed by age, sex and were comparable to majority of previous studies. There was no obvious change for overall trend over time, which may be able to address safety concerns on risk of intussusception after newly introduced rotavirus vaccine in Chinese children.