Abstract
Introduction: Prompt and accurate diagnosis of COVID-19 is crucial as part of the prevention and control strategy for the pandemic. Antigen-detecting rapid diagnostic tests (Ag-RDTs) are reasonably priced, easily accessible, and easy to use with rapid turn-around-time as an alternative to the limited gold-standard real-time reverse-transcription polymerase chain reaction (rRT-PCR) tests. In early 2021, Kelantan experienced influxes of COVID-19 cases, causing a high burden on centralised laboratories running rRT-PCR. Ag-RDTs as a diagnostic tool would be advantageous, but at the time of this study, the data on their field performance was quite limited. This study evaluated the Ag-RDTs for COVID-19 diagnosis in a community setting with high disease prevalence in Kelantan.
Methods: This is a cross-sectional study conducted in Kelantan in May 2021. We retrieved the state's data from the National Public Health Laboratory System registered from epidemiology week 13 to 22 in the year 2021. A total of 2569 individuals attended COVID-19 testing facilities in Kelantan with two nasopharyngeal specimens taken not more than 24 hours apart and tested for COVID-19 by both Ag-RDTs and rRT-PCR were analysed. The overall diagnostic performance of Ag-RDTs was evaluated with rRT-PCR as the gold standard. Subgroup analyses were performed based on the demographic characteristics, symptoms at the time of sampling, screening purposes, exposure risks, and cycle threshold (Ct) value. Results: The agreement between Ag-RDTs and RT-PCR was excellent (?= 0.828; 95% CI: 0.806,0.851; P <0.001). Ag-RDTs had an overall specificity of 96.2% (95% CI: 95.1%,97.1%), a sensitivity of 85.4% (95% CI: 83.1%,87.5%), and an accuracy of 92.5% (95% CI: 91.4%,93.5%). The positive (PPV) and negative predictive value (NPV) at 35% prevalence were 92.0% (95% CI: 90.0%,93.7%) and 92.8% (95% CI: 91.7%,93.7%) respectively. The mean Ct value was significantly lower in 873 (37.0%) true-positive cases compared to 149 (71.6%) false-negative cases (23.3 vs 29.9, t (1020)=-14.57, P <0.001). The sensitivity was higher ( P <0.001) in those with high viral load (Ct value ?25.0) at 85.2% (95% CI: 93.2, 96.8%) compared to individuals with intermediate (84.5%; 95% CI: 79.3%, 88.9%) and low viral load (53.6%; 95%CI: 46.0%, 61.1%). The sensitivity of Ag-RDTs was found to be significantly lower among asymptomatic close contacts at 78.8% (95%CI: 72.9%,84.01%) and those aged ?18 years old at 67.7% (95%CI: 61.2%, 73.8%). The Ag-RDTs performed well when the expected prevalence was between 10% to 60%, but the NPV continued to decrease as the prevalence increased.
Interpretation & conclusion: Overall, Ag-RDTs are reliable alternatives to rRT-PCR in a community setting with high disease prevalence. The specificities of Ag-RDTs in diagnosing COVID-19 were consistently high in all subgroup analyses. However, the sensitivities vary, with lower sensitivity observed among individuals with low viral load, asymptomatic cases, and younger age groups. The Ag-RDTs allow rapid identification of highly infectious cases, making it a useful tool in diagnosing COVID-19, but with some considerations. Given its lower sensitivity among younger cases and lower NPV among subpopulations with a very high disease prevalence, such as symptomatic close contacts, these groups tested negative by Ag-RDTs may require confirmation by rRT-PCR.
Links
- https://apcph.cphm.my/wp-content/uploads/2022/07/APCPH2022-O-56.pdf
- https://apcph.cphm.my/events/oral-session-1-ballroom-A/
BibTeX (Download)
@proceedings{APCPH2022-O-56,
title = {The Performance of Antigen-detecting Rapid Diagnostic Tests for Coronavirus Disease (COVID-19) in A Community Setting in Kelantan, Malaysia},
author = {Hazlienor Mohd Hatta and Nik Mohd Hafiz Mohd Fuzi and Suhaiza Sulaiman and Abdul Haris Muhammad and Zaini Hussin},
url = {https://apcph.cphm.my/wp-content/uploads/2022/07/APCPH2022-O-56.pdf
https://apcph.cphm.my/events/oral-session-1-ballroom-A/},
year = {2022},
date = {2022-08-01},
urldate = {2022-08-02},
issue = {7},
abstract = {Introduction: Prompt and accurate diagnosis of COVID-19 is crucial as part of the prevention and control strategy for the pandemic. Antigen-detecting rapid diagnostic tests (Ag-RDTs) are reasonably priced, easily accessible, and easy to use with rapid turn-around-time as an alternative to the limited gold-standard real-time reverse-transcription polymerase chain reaction (rRT-PCR) tests. In early 2021, Kelantan experienced influxes of COVID-19 cases, causing a high burden on centralised laboratories running rRT-PCR. Ag-RDTs as a diagnostic tool would be advantageous, but at the time of this study, the data on their field performance was quite limited. This study evaluated the Ag-RDTs for COVID-19 diagnosis in a community setting with high disease prevalence in Kelantan.
Methods: This is a cross-sectional study conducted in Kelantan in May 2021. We retrieved the state's data from the National Public Health Laboratory System registered from epidemiology week 13 to 22 in the year 2021. A total of 2569 individuals attended COVID-19 testing facilities in Kelantan with two nasopharyngeal specimens taken not more than 24 hours apart and tested for COVID-19 by both Ag-RDTs and rRT-PCR were analysed. The overall diagnostic performance of Ag-RDTs was evaluated with rRT-PCR as the gold standard. Subgroup analyses were performed based on the demographic characteristics, symptoms at the time of sampling, screening purposes, exposure risks, and cycle threshold (Ct) value. Results: The agreement between Ag-RDTs and RT-PCR was excellent (?= 0.828; 95% CI: 0.806,0.851; P \<0.001). Ag-RDTs had an overall specificity of 96.2% (95% CI: 95.1%,97.1%), a sensitivity of 85.4% (95% CI: 83.1%,87.5%), and an accuracy of 92.5% (95% CI: 91.4%,93.5%). The positive (PPV) and negative predictive value (NPV) at 35% prevalence were 92.0% (95% CI: 90.0%,93.7%) and 92.8% (95% CI: 91.7%,93.7%) respectively. The mean Ct value was significantly lower in 873 (37.0%) true-positive cases compared to 149 (71.6%) false-negative cases (23.3 vs 29.9, t (1020)=-14.57, P \<0.001). The sensitivity was higher ( P \<0.001) in those with high viral load (Ct value ?25.0) at 85.2% (95% CI: 93.2, 96.8%) compared to individuals with intermediate (84.5%; 95% CI: 79.3%, 88.9%) and low viral load (53.6%; 95%CI: 46.0%, 61.1%). The sensitivity of Ag-RDTs was found to be significantly lower among asymptomatic close contacts at 78.8% (95%CI: 72.9%,84.01%) and those aged ?18 years old at 67.7% (95%CI: 61.2%, 73.8%). The Ag-RDTs performed well when the expected prevalence was between 10% to 60%, but the NPV continued to decrease as the prevalence increased.
Interpretation \& conclusion: Overall, Ag-RDTs are reliable alternatives to rRT-PCR in a community setting with high disease prevalence. The specificities of Ag-RDTs in diagnosing COVID-19 were consistently high in all subgroup analyses. However, the sensitivities vary, with lower sensitivity observed among individuals with low viral load, asymptomatic cases, and younger age groups. The Ag-RDTs allow rapid identification of highly infectious cases, making it a useful tool in diagnosing COVID-19, but with some considerations. Given its lower sensitivity among younger cases and lower NPV among subpopulations with a very high disease prevalence, such as symptomatic close contacts, these groups tested negative by Ag-RDTs may require confirmation by rRT-PCR.},
howpublished = {published online at https://apcph.cphm.my},
note = {Type: ORAL PRESENTATION; Organisation: Communicable Disease Control Unit, Kelantan State Health Department; Surveillance Unit, Kelantan State Health Department; Public Health Division, Kelantan State Health Department},
keywords = {Covid-19, diagnostic performance, Rapid Antigen Test},
pubstate = {published},
tppubtype = {proceedings}
}