Factors Affecting SARS-CoV-2 Test Discordance in Skilled Nursing Facilities

Area of Science:

• Infectious Diseases
• Diagnostic Testing
• Public Health

Background:

• Reverse transcription polymerase chain reaction (PCR) and antigen tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are sometimes discordant.
• Skilled nursing facilities (SNFs) require accurate and timely diagnostic testing for SARS-CoV-2 to manage outbreaks.

Purpose of the Study:

• To evaluate the discordance between SARS-CoV-2 antigen and PCR tests in SNFs.
• To assess the relationship between symptom presence, timing between tests, and facility outbreaks on test discordance.

Main Methods:

• An observational study using electronic health record data from 306 SNFs.
• Identified SARS-CoV-2 antigen and PCR tests conducted within 2 days of each other.
• Classified symptom presence and facility outbreak status at the time of testing.

Main Results:

• Of 171,280 antigen tests, 12.3% were followed by a PCR test within 2 days.
• Discordance was low overall (0.8% of antigen tests false negative by PCR, 0.2% false positive).
• Discordance was higher in symptomatic residents and during facility outbreaks.

Conclusions:

• Discordance between SARS-CoV-2 antigen and PCR tests in SNFs is generally low.
• Symptom presence and facility outbreaks are associated with increased test discordance.
• A strategy combining antigen testing with PCR confirmation appears effective for SARS-CoV-2 case identification in SNFs.