Available online 3 May 2023, 115977

Analytical sensitivity antigen tests similar for Omicron and pre-Delta variants

Loss of analytical sensitivity for detection Omicron variant only at low viral load

Fluorescence immunoassay more sensitive than lateral flow antigen at low viral load

Analytical sensitivity of two rapid antigen tests was evaluated for detection of presumed SARS-CoV-2 Omicron variants and earlier variants of concern.

152 SARS-CoV-2 RNA positive samples (N and ORF1ab positive but S gene negative) were tested for SARS-CoV-2 antigen by ACON lateral flow and LumiraDx fluorescence immunoassays. Sensitivity within 3 viral load ranges was compared among these 152 samples and 194 similarly characterized samples collected prior to the circulation of the Delta variant (pre-Delta).

Antigen was detected in >95% of pre-Delta and presumed Omicron samples for both tests at viral loads >500,000 copies/mL, and 65 to 85% of samples with 50,000-500,000 copies/mL. At viral load <50,000 copies/mL, antigen tests showed better sensitivity in detecting pre-Delta compared to Omicron variants. LumiraDx was more sensitive than ACON at low viral load.

Antigen tests had decreased sensitivity for detecting presumed Omicron compared to pre-Delta variants at low viral load.

SARS-CoV-2

antigen

rapid diagnostic test

Omicron

severe acute respiratory syndrome coronavirus 2

reverse transcription quantitative polymerase chain reaction

rapid antigen diagnostic tests

fluorescence immunoassay

Clinical Laboratory Improvement Amendments

emergency use authorization

United States Food and Drug Administration

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