ABSTRACT
Safe and effective vaccines are crucial to control Covid-19 and to protect persons who are at high risk of complications or death. Test-negative design is a popular option for evaluating the effectiveness of Covid-19 vaccines, but the findings could be biased by several factors, including imperfect sensitivity and/or specificity of the test used for the SARS-Cov-2 infection.We propose a simple Bayesian modeling approach for estimating vaccine effectiveness that is robust even when the diagnostic test is imperfect.We use simulation studies to demonstrate this robustness to misclassification bias for estimating Covid-19 vaccine effectiveness, and illustrate the utility of our approach using real-world examples
Subject(s)
COVID-19ABSTRACT
Background Rapid diagnostics are vital for curving the transmission and control of COVID-19 pandemic. Although many commercially available antigen-based rapid diagnostic tests (Ag-RDTs) for the detection of SARS-CoV-2 are recommended by the WHO, their diagnostic performance has not yet been assessed in Ethiopia. So far, the vast majority of studies assessing diagnostic accuracies of rapid antigen tests considered RT-PCR as a gold standard, which inevitably leads to bias when RT-PCR is not 100% sensitive and specific. Thus, this study aimed to evaluate the diagnostic performance of Panbio COVID-19 rapid antigen test jointly together with the RT-PCR for the detection of SARS-CoV-2. Methods A prospective cross-sectional study was done from July to September 2021 in Addis Ababa, Ethiopia, during the third wave of the pandemic involving two health centers and two hospitals. Diagnostic sensitivity and specificity of Panbio rapid antigen test and RT-PCR were obtained using Bayesian Latent-Class Models (BLCM). Results 438 COVID-19 presumptive clients were enrolled, 239 (54.6%) were females, of whom 196 (44.7%) had a positive RT-PCR and 158 (36.1%) were Ag-RDT positive. The Ag-RDT and RT-PCR had a sensitivity (95% CrI) of 99.6 (98.4- 100), 89.3 (83.2- 97.6) and specificity (95% CrI) of 93.4 (82.3 - 100), 99.1 (97.5- 100) respectively. Most of the study participants, 318 (72.6) exhibited COVID-19 symptoms and the most reported was cough 191 (43.6). Conclusion The diagnostic performance of Panbio COVID-19 Ag RDT is coherent with the WHO established criteria of having a sensitivity [≥]80% for Ag-RDTs. Superior performance of the Panbio RDT was documented in samples with the lowest cycle-threshold RT-PCR values and clients with confirmed clinical symptoms. Thus, we recommend the use of the Panbio RDT for both symptomatic and asymptomatic individuals in clinical settings for screening purposes.
Subject(s)
COVID-19ABSTRACT
The objective of this work was to estimate the diagnostic accuracy of RT-PCR and Lateral flow immunoassay tests (LFIA) for COVID-19, depending on the time post symptom onset. Based on the cross-classified results of RT-PCR and LFIA, we used Bayesian latent class models (BLCMs), which do not require a gold standard for the evaluation of diagnostics. Data were extracted from studies that evaluated LFIA (IgG and/or IgM) assays using RT-PCR as the reference method. The cross-classified results of LFIA and RT-PCR were analysed separately for the first, second and third week post symptom onset. The Se RT-PCR was 0.695 (95% probability intervals: 0.563; 0.837) for the first week and remained similar for the second and the third week. The Se IgG/M was 0.318 (0.229; 0.416) for the first week and increased steadily. It was 0.755 (0.673; 0.829) and 0.927 (0.881; 0.965) for the second and third week, respectively. Both tests had a high to absolute Sp , with point median estimates for Sp RT-PCR being consistently higher. Sp RT-PCR was 0.990 (0.980; 0.998) for the first week. The corresponding value for Sp IgG/M was 0.962 (0.905; 0.998). Further, Sp estimates for each test did not differ between weeks. BLCMs provide a valid and efficient alternative for evaluating the rapidly evolving diagnostics for COVID-19, under various clinical settings and for different risk profiles.