Frequency ratio of AIP to PCT among different geographic regions. For all listed regions, except China, the frequency ratio of AIP to PCT is obtained by dividing the prevalence rates of AIP to PCT in the indicated region (supplemental Table 1). For China, the frequency ratio of AIP to PCT is estimated by dividing the number of AIP cases by the number of PCT cases as reported between 2003 and 2019 in the Chinese medical database Wanfang Med Online (WMO; http://med.wanfangdata.com.cn/).