Effect of the large waves of COVID-19 on false-positive results in annual lung cancer screening.
Authors: Kimura Tatsuo , Fukumoto Shinya , Nakano Akemi , Uchida Sawako , Nadatani Yuji , Tauchi Yukie , Takashima Shingo , Nishii Yuko , Mitsuoka Shigeki , Ogawa Koichi , Ageshio Naomi , Watanabe Toshio 
Published: June 2023

e18596 Background: Chest X ray (CXR) has been the most common screen test procedure for detection of lung cancer. We have shown that repeat visitors (R) had a significantly lower proportion of CXR abnormalities requiring medication than the first-time visitors (F) at annual lung cancer screening. (Kimura T. Health Prim Car, 2021). In 2022, Japan experienced three large waves of COVID-19 mainly the Omicron variants (the 6th: Jan-Mar, the 7th: Jul-Sep and the 8th: Oct to present). The later the wave, the larger the scale. The Omicron variant spreads more easily than the original or the Delta variants up to the 5th waves. The hypothesis was that these COVID waves may have influenced lung cancer screening. Methods: Our clinic “MedCity21” is a university outpatient clinic for a complete medical check-up as part of a private health screening program. Of course, we check temperature, respiratory symptoms, and any history of COVID infection and vaccination of the participants (pts). Our facility allows COVID-infected pts to have medical check-ups four weeks after they are cured. The pts with abnormalities detected on CXR were notified by telephone request and invited to our specialty clinic for chest CT scan as further examination. Each year from 2018 to 2022, we examined the varieties of abnormal shadows on CXR and CT scans and compared the differences between 2022 and each year before to 2022 using the chi-squared tests. Results: In 2022, there were 14522 pts of which F and R were 27.1% and 72.9% respectively. The percentage of pts with a history of COVID was 1.68% in January, but gradually increased, reaching a plateau of 20% in October. There were 231pts (1.6%) with CXR abnormalities requiring further investigation. The rates in F and R were 1.3% and 1.7%, respectively. A total of 132 pts (56.7%) of 63 pts in F and 69 pts in R underwent chest CT scans at our facility after the call for recommendation for further investigation. The distribution of CXR and CT variations was consistent with our previous report. There was one confirmed case of lung cancer among F, and 2 among R in 2022. It should be noted that the CT confirmation revealed that there were 10 pts with nodular shadow on CXR, of whom 5 were found to have COVID infection after 1 month follow-up. Conclusions: There was a significant decrease in the number of first-time visitors in 2022 compared to previous years (p < 0.001). The percentage of cases returning to our clinic for CT for further investigation has decreased dramatically (p < 0.001). These were attributed to the large COVID waves. Notably, for the first time in the last 5 years, the detection rates of CXR abnormalities were reversed for R and F. In some cases, nodule shadows were difficult to determine whether they were lung cancer or COVID. The number of people with previous COVID-19 infection will continue to increase. The COVID pandemic and subsequent behavioral changes have affected the way people manage their health status.