Cost-effectiveness of antigen testing for ending COVID-19 isolation

Comparing SARS-CoV-2 testing positivity rates and COVID-19 impact among different isolation strategies: a rapid systematic review and a modelling study

Background

The optimal isolation duration for patients with COVID-19 remains unclear. To support an update of World Health Organization (WHO)'s Living Clinical management guidelines for COVID-19 (https://www.who.int/publications/i/item/WHO-2019-nCoV-clinical-2022.2), this rapid systematic review and modelling study addresses the effects of different isolation periods for preventing onward transmission leading to hospitalisation and death among secondary cases.

Methods

We searched the WHO COVID-19 database for studies up to Feb 27, 2023. We included clinical studies of any design with COVID-19 patients confirmed by PCR test or rapid antigen test addressing the impact of any isolation strategy on preventing the spread of COVID-19. There were no restrictions on publication language, publication status, age of patients, severity of COVID-19, variants of SARS-COV-2, comorbidity of patients, isolation location, or co-interventions. We performed random-effects meta-analyses to summarise testing rates of persistent test positivity rates after COVID-19 infection. We performed pre-specified subgroup analyses by symptom status and meta-regression analyses for the proportion of fully vaccinated patients. We developed a model to compare the effects of three isolation strategies on onward transmission leading to hospitalisation and death. The three isolation strategies were (1) 5-day isolation, with no test to release; (2) removal of isolation based on a negative test; and (3) 10-day isolation, with no test to release. The model incorporates estimates of test positivity rates, effective reproduction number, isolation adherence, false negative rate, and hospitalisation rates or case fatality rates. To assess the impact of varying isolation adherence and false negative rates on rapid antigen testing, we conducted some sensitivity analyses. We used the Grading of Recommendations Assessment, Development and Evaluation approach to assess certainty of evidence. The protocol is registered with PROSPERO (CRD42022348626).

Findings

Fifteen studies addressing persistent test positivity rates including 4188 patients proved eligible. Asymptomatic patients (27.1%, 95% CI: 15.8%-40.0%) had a significantly lower rapid antigen test positive rate than symptomatic patients (68.1%, 95% CI: 40.6%-90.3%) on day 5. The rapid antigen test positive rate was 21.5% (95% CI: 0-64.1%; moderate certainty) on day 10. Our modelling study suggested that the risk difference (RD) for asymptomatic patients between 5-day isolation and 10-day isolation in hospitalisations (23 more hospitalisations of secondary cases per 10,000 patients isolated, 95% uncertainty interval (UI) 14 more to 33 more) and mortality (5 more per 10,000 patients, 95% UI 1 to 9 more) of secondary cases proved very small (very low certainty). For symptomatic patients, the potential impact of 5- versus 10-day isolation was much greater in hospitalisations (RD 186 more per 10,000 patients, 95% UI 113 more to 276 more; very low certainty) and mortality (RD 41 more per 10,000 patients, 95% UI 11 more to 73 more; very low certainty). There may be little or no difference between removing isolation based on a negative antigen test and 10-day isolation in the onward transmission leading to hospitalisation or death, but the average isolation period (mean difference -3 days) will be shorter for the removal of isolation based on a negative antigen test (moderate certainty).

Interpretation

5 days versus 10 days of isolation in asymptomatic patients may result in a small amount of onward transmission and negligible hospitalisation and mortality; however, in symptomatic patients, the level of onward transmission is concerning and may lead to high hospitalisation and death rates. The evidence is, however, very uncertain.

Funding

This work was done in collaboration with WHO.

An Economic Evaluation of Government-Funded COVID-19 Testing in Australia

OBJECTIVE

Easy and equitable access to testing has been a cornerstone of the public health response to COVID-19. Currently in Australia, testing using polymerase chain reaction (PCR) tests for COVID-19 is free to the user, but government funding for rapid antigen tests (RATs) is limited. We conduct an economic analysis of alternative government policies regarding the funding of COVID-19 testing in Australia.

METHODS

A decision tree model was developed to describe COVID-19 testing pathways for the Australian population over a 1-week period. The model outputs were analysed to estimate R numbers associated with alternative funding policies, which were used to estimate COVID-19 cases over a 6-month time horizon. Healthcare costs and quality-adjusted life-year (QALY) effects were applied to new COVID-19 cases. The model was populated using responses to a de novo population survey and published data sources.

RESULTS

Compared with no government-funded COVID-19 testing, government-funded testing is estimated to generate large incremental net monetary benefits (INMBs), up to A$15 billion in the base-case analyses. Government-funded PCR testing and RATs for all is predicted to maximise INMBs in most tested scenarios, though funding RATs for all and not PCR tests has similar INMBs in many scenarios and generates higher benefits to costs ratios.

CONCLUSIONS

Our interpretation of the modelled analysis is that at the time of writing (July 2022), with high vaccination uptake in Australia and few other public health measures in place, Australian governments should consider reducing funding of PCR testing, for example, limiting capacity to essential workers and individuals with known risk factors for serious symptoms, and fund RATs for all.