Development and external validation of the DOAT and DOATS scores: simple decision support tools to identify disease progression among nonelderly patients with mild/moderate COVID-19
Authors: Shibata Yoko , Omae Kenji , Minemura Hiroyuki , Suzuki Yasuhito , Nikaido Takefumi , Tanino Yoshinori , Fukuhara Atsuro , Kanno Ryuzo , Saito Hiroyuki , Suzuki Shuzo , Ishii Taeko , Inokoshi Yayoi , Sando Eiichiro , Sakuma Hirofumi , Kobayashi Tatsuho , Kume Hiroaki , Kamimoto Masahiro , Aoki Hideko , Takama Akira , Kamiyama Takamichi , Nakayama Masaru , Saito Kiyoshi , Tanigawa Koichi , Sato Masahiko , Kambe Toshiyuki , Kanzaki Norio , Azuma Teruhisa , Sakamoto Keiji , Nakamura Yuichi , Ohtani Hiroshi , Waragai Mitsuru , Maeda Shinsaku , Ishida Tokiya , Sugino Keishi , Inage Minoru , Hirama Noriyuki , Furuyama Kodai , Fukushima Shigeyuki , Saito Hiroshi , Machiya Jun-ichi , Machida Hiroyoshi , Abe Koya , Iwabuchi Katsuyoshi , Katagiri Yuji , Aida Yasuko , Abe Yuki , Ota Takahito , Ishizawa Yuki , Tsukada Yasuhiko , Yamada Ryuki , Sato Riko , Onuma Takumi , Tomita Hikaru , Saito Mikako , Watanabe Natsumi , Rikimaru Mami , Kawamata Takaya , Umeda Takashi , Morimoto Julia , Togawa Ryuichi , Sato Yuki , Saito Junpei , Kanazawa Kenya , Kurita Noriaki , Iseki Ken 
Published: August 2023

Abstract
Background
During the fifth wave of the coronavirus disease 2019 (COVID-19) pandemic in Japan, which took place between June and September 2021, a significant number of COVID-19 cases with deterioration occurred in unvaccinated individuals < 65 years old. However, the risk factors for COVID-19 deterioration in this specific population have not yet been determined. This study developed a prediction method to identify COVID-19 patients < 65 years old who are at a high risk of deterioration.

Methods
This retrospective study analyzed data from 1,675 patients < 65 years old who were admitted to acute care institutions in Fukushima with mild-to-moderate-1 COVID-19 based on the Japanese disease severity criteria prior to the fifth wave. For validation, 324 similar patients were enrolled from 3 hospitals in Yamagata. Logistic regression analyses using cluster-robust variance estimation were used to determine predictors of disease deterioration, followed by creation of risk prediction scores. Disease deterioration was defined as the initiation of medication for COVID-19, oxygen inhalation, or mechanical ventilation starting one day or later after admission.

Results
The patients whose condition deteriorated (8.6%) tended to be older, male, have histories of smoking, and have high body temperatures, low oxygen saturation values, and comorbidities, such as diabetes/obesity and hypertension. Stepwise variable selection using logistic regression to predict COVID-19 deterioration retained comorbidities of diabetes/obesity (DO), age (A), body temperature (T), and oxygen saturation (S). Two predictive scores were created based on the optimism-corrected regression coefficients: the DOATS score, including all of the above risk factors, and the DOAT score, which was the DOATS score without oxygen saturation. In the original cohort, the areas under the receiver operating characteristic curve (AUROCs) of the DOATS and DOAT scores were 0.81 (95% confidence interval [CI] 0.77–0.85) and 0.80 (95% CI 0.76–0.84), respectively. In the validation cohort, the AUROCs for each score were both 0.76 (95% CI 0.69–0.83), and the calibration slopes were both 0.80. A decision curve analysis confirmed the clinical practicability of both scores in the validation cohort.

Conclusions
We established two prediction scores that can quickly evaluate the risk of COVID-19 deterioration in mild/moderate patients < 65 years old.