# P-1647. Duration of SARS-CoV-2 Detection with Rapid Antigen Tests and Nucleic Acid Amplification Tests in a 2024 Nursing Home Resident Cohort

## TL;DR

This study compares how long SARS-CoV-2 can be detected in nursing home residents using rapid antigen tests versus more sensitive nucleic acid tests.

## Contribution

The study provides updated 2024 data on SARS-CoV-2 detection duration in nursing home residents using rapid antigen and nucleic acid amplification tests.

## Key findings

- Rapid antigen tests detected SARS-CoV-2 for a median of 7 days in nursing home residents.
- Nucleic acid amplification tests detected SARS-CoV-2 for a median of 14 days in the same population.
- The duration of detection has remained consistent compared to previous seasons.

## Abstract

Nursing home (NH) residents are at high risk of contracting and having adverse outcomes from SARS-CoV-2. Based on culture positivity CDC currently recommends 10-day transmission-based precautions; greater understanding of the duration of SARS-CoV-2 detection with rapid antigen tests (RAT) and nucleic acid amplification tests (NAAT), can further guide testing and isolation recommendations to reduce transmission. In a 2023 NH cohort with daily testing, the median duration of SARS-CoV-2 detection among NH residents was six days for RAT and 11 days for NAAT. We update estimates of SARS-CoV-2 detection duration in a 2024 cohort of NH residents to inform prevention efforts.Figure 1:Kaplan-Meier analysis was restricted to residents with ≥4 RAT (n = 88) or NAAT (n = 84). A resident could be in both RAT and NAAT survival curves. The median duration of SARS-CoV-2 detection with RAT was seven days and the median duration of SARS-CoV-2 detection with NAAT was 14 days.

Kaplan-Meier analysis was restricted to residents with ≥4 RAT (n = 88) or NAAT (n = 84). A resident could be in both RAT and NAAT survival curves. The median duration of SARS-CoV-2 detection with RAT was seven days and the median duration of SARS-CoV-2 detection with NAAT was 14 days.

We collected data on NH residents tested for SARS-CoV-2 with RAT and NAAT in 17 NHs across eight states. Residents could enroll upon a positive SARS-CoV-2 RAT or NAAT followed by paired nasal specimen collection every 3-5 days for up to 30 days. We abstracted resident clinical characteristics from available medical records. We used Kaplan-Meier (KM) survival analysis to estimate the time from first positive (day 0) to first negative. We restricted analyses to residents with ≥ 4 RAT or NAAT to capture the duration of SARS-CoV-2 positivity; residents could be in both RAT and NAAT survival curves. We used Greenwood’s formula to calculate 95% confidence intervals (CI).

We enrolled 121 residents with a positive SARS-CoV-2 test, of whom 87 (72%) were vaccinated. Eighty-five participants (70%) had a Charlson Comorbidity Index score ≥5. Sixty-eight participants received antivirals (n=36 [53%] molnupiravir; n=28 [41%] nirmatrelvir/ritonavir; n=4 [6%] remdesivir). The KM analysis included 88 (73%) and 84 (69%) residents with ≥ 4 RAT and NAAT, respectively. The median duration of SARS-CoV-2 detection with RAT was seven days; 61% and 21% had SARS-CoV-2 detection at five and 10 days, respectively (Figure 1). The median duration of SARS-CoV-2 detection with NAAT was 14 days; 94% and 75% had SARS-CoV-2 detection at five and 10 days, respectively.

The median time from first positive to first negative test for NH residents with RAT was 7 days and 14 days for NAAT. The duration of SARS-CoV-2 detection among NH residents has not substantially changed since last season.

Yasin Abul, MD, CDC/ABT: Grant/Research Support|CLARIO: Advisor/Consultant|GSK: Grant/Research Support|Moderna: Grant/Research Support|Seqirus: Grant/Research Support David Canaday, MD, Moderna: Grant/Research Support|Pfizer: Grant/Research Support|Seqirus: Advisor/Consultant|Seqirus: Grant/Research Support|Seqirus: Honoraria Christopher J. Crnich, MD, PhD, Merck: Grant/Research Support Samantha Fuller, MPH, AstraZeneca: Grant/Research Support|CSL Vifor: Grant/Research Support|GlaxoSmithKline: Grant/Research Support Jon P. Furuno, PhD, Merck: Grant/Research Support Stefan Gravenstein, MD, MPH, GSK: Advisor/Consultant|GSK: Grant/Research Support|GSK: Honoraria|Moderna: Grant/Research Support|Novavax: Advisor/Consultant|Novavax: Honoraria|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Grant/Research Support|Sanofi: Honoraria|Seqirus: Grant/Research Support Jennifer K. Meece, PhD, CSL Seqirus: Grant/Research Support|GSK: Grant/Research Support|ModernaTX: Grant/Research Support Lona Mody, MD, MS, Nanovibronix: Grant/Research Support|NIH, CDC, VA: Grant/Research Support|UpToDate: Honoraria Morgan Katz, MD, MHS, Skinclique: Advisor/Consultant