Background: Given the ongoing impact of the COVID-19 pandemic, self-risk assessment tools are crucial for individuals, particularly the working-age group, to evaluate their infection risk. There is a lack of such tools as of early 2021.

Objective: To develop and evaluate the effectiveness of the self-assessment test application named Thai Save Thai (TST) for determining individuals’ risk level of COVID-19 infection before entering premises.

Materials and Methods: The present research consisted of two phases between April 2021 and July 2022. In the first phase, factory workers from all regions of the country were recruited using population allocation sampling. TST was used for self-assessment three times within two-week period to determine risk levels. The second phase evaluated the sensitivity, specificity and predictive value of TST among 320 subjects underwent reverse transcription polymerase chain reaction (RT-PCR) testing.

Results: TST showed varying percentages for each risk level: normal, 44.4%, 38.8%, 29.2%; low, 54.3%, 60.8%, 70.5%; high, 0.2%, 0.02%, 0.1%; very high, 1.1%, 0.36%, 0.21%; and infection results, 0.02%, 0%, 0.05%. TST indicated a sensitivity of 95.7% (95% CI 87.3 to 104.0), a specificity of 75.0% (95% CI 63.2 to 86.8) for detecting infection. Sensitivity for very high-risk level was 85.7% (95% CI 59.8 to 111.6) with 63.9% specificity (95% CI 51.9 to 76.0). The high-risk level had a sensitivity of 75% (95% CI 32.6 to 117) with specificity of 28.1% (95% CI 20.6 to 35.5), while the low-risk level had sensitivity of 90% (95% CI 71.4 to 109.0) with specificity of 27.1% (95% CI 19.8 to 34.3). The negative predictive value (NPV) were the same value as 97.5% at all results.

Conclusion: TST application is a self-risk screening tool that effectively discriminates between different risk levels and provides sensitivity for detecting infection with NPV for all assessment results. This application can enable individuals to assess their risk level of COVID-19 infection before entering any premises.

Keywords: Self-risk assessment; COVID-19; Infection; Verify of entry; Working-age

DOI: 10.35755/jmedassocthai.2023.06.13860

Received 28 March 2023 | Revised 19 May 2023 | Accepted 19 May 2023