CXR for PTB screening in high schools were performed by community-level medical and health care institutions in most cases in China. Usually, there were no external quality control measures over the CXR reading in PTB screening in high schools. The current situation of CXR implementation lacked baseline surveys. Through this study, we have obtained PTB and suspected PTB burden among high school students in Chongqing.
In this study, active PTB diagnoses are all derived from suspected cases with abnormal CXR results, and CXR played an important role in PTB screening in high schools. A study found that asymptomatic children with abnormal radiographs were 25.1-fold more likely to have TB in 4468 TB-exposed children between September 2009 and August 2012 [14]. Amanda G et al [15] have found that 60 had CXR findings suggestive of TB in 268 TB-infected children. A mass CXR programme have significantly contributed to TB control in high-burdened population in Cape Town, South Africa [16]. It could be seen that CXR played an important role in TB screening in different regions and populations.
The PTB detection rate conducted by Chongqing Municipal Institute of Tuberculosis was 57 cases per 100000 population between January 2022 and December 2022in high schools in Chongqing. PANG Y et al [13] have found that the PTB detection rate conducted by community-level medical and health care institutions was 34.8 cases per 100000 population in 2021 in high schools in Chongqing, which was lower than PTB detection rate conducted by Chongqing Municipal Institute of Tuberculosis. A study has found that the quality of CXR conducted by community-level medical and health care institution was poor in contact investigation of a school clustered outbreak in Chongqing, resulting in failure to detect cases who have already suffered from PTB [8]. The suspected PTB detection gap from CXR may exist in schools.
The occurrence of suspected PTB detection gap from CXR may be due to the instability of CXR reading. Andronikou S et al [17] have found that inter-reader agreement was only moderate (kappa 0.4–0.6) in a retrospective study for interobserver agreement between paediatric radiologists interpreting PTB screening CXR in children in the UK. A study found that Only 60% of the CXR were reported as moderate to good quality, and interobserver agreement on quality was slight to moderate (kappa 0.16–0.35) the context of community-based screening of child PTB contacts [18]. Berteloot L et al [19] have found that CXR showed poor-to-fair inter-reader agreement and limited diagnostic accuracy for PTB in HIV-infected children in resource-limited countries. This situation may be common in community-level medical and health care institutions that lack regular standardized training and quality control.
Solutions to this problem include conducting regular standardized training to CXR reading in PTB screening in schools. A study found that correct diagnosis has been increased and sensitivity has been improved for CXR interpretation of suspected PTB after a short skill-development course [20]. Seddon JA et al [21] have found that teaching clinicians with a 1-day training course would lead to a limited improvement in CXR reading ability (P = 0.017). María ML et al [22] have found that a standardized CXR reading protocol showed good agreement and improves the CXR interpretation reproducibility, and global agreement reached 91.3% (kappa = 0.51).
Teleradiology was also a way to address the quality of CXR interpretation. Teleradiology is a mechanism to overcome the lack of on-site experienced radiologists and can benefit children in developing countries [23]. In recent years, artificial intelligence (AI) has made rapid progress in the interpretation of CXR and has begun to be applied to community-based PTB screening. Shibu V et al [24] have found that approximately 15.8% PTB detection increase could be attributed to AI in a active case-finding program in a resource-limited region in India where AI was used for PTB screening using CXR. Kosuke O et al [25] have found that the human reading needed fell to 21%, and AI was applicable to community-based active case-finding in high TB burden settings where experienced human readers for CXR images were scarce.
In our study, the suspected PTB detection rate in Southeast Districts was the highest, and the PTB detection rate was also the highest. This regional disparity indicates that the PTB screening efforts in this region need to be further strengthened. According to Chongqing Statistical Yearbook, the GDP per capita of Southeast Districts was the lowest in all four regions in Chongqing. The lowest socioeconomic status may lead to the highest suspected PTB detection. Other previous studies have also identified similar regional disparity. In a student TB spatiotemporal analysis in 2014–2019 in Chongqing, PANG Y et al [26] have found that Southeast Districts was a high PTB burden region and also a high-risk region for transmission due to socioeconomic status and screening quality. FAN J et al [27] have found that the student PTB epidemic in Southeast Districts was the highest with an average annual notification rate of 88.31 cases per 100000 population from 2008 to 2019.
The impact of socioeconomic status on the prevalence of student PTB was also found when comparing Chongqing with other developed regions. A study has found that the notification rate of PTB among students in Shanghai remained between 15 and 20 cases per 100000 population from 2009 to 2017, which was far lower that in Chongqing [28]. A study has also found that the western region in China had a higher PTB epidemic, which included Chongqing [29].
CXR has limitations in imaging modalities for PTB. A study has found that findings compatible with TB were more frequently detected on computed tomography (CT) than CXR, which could be performed when in doubt [30]. Charlotte CH et al have found that ultrasound detected abnormalities more frequently than CXR with higher inter-reader agreement, which may be a promising modality for detecting abnormalities in PTB [31, 32].
In conclusion, CXR has played a significant role in PTB screening in high schools in the Chongqing, effectively controlling the student TB epidemic. However, there may be a need to focus on the CXR quality control at the grassroots level and strengthen policy support for Southeast Districts in Chongqing.