Is the Binax COVID+Flu Combo Test a PCR Test?
No, the BinaxNOW COVID+Flu combo test is not a PCR test but rather a rapid antigen test that detects viral proteins rather than viral genetic material. 1, 2
Understanding COVID-19 Testing Types
PCR Tests (Molecular Tests)
- RT-PCR (Reverse Transcription-Polymerase Chain Reaction) is the gold standard for COVID-19 diagnosis, detecting viral RNA with high sensitivity and specificity 3
- PCR tests typically have a turnaround time of 6-8 hours but can be as quick as 45 minutes in some settings 3
- Target genes tested in PCR include RNA-dependent RNA polymerase (RdRp), open reading frame (ORF1), Envelope (E), and nucleocapsid (N) genes of the SARS-CoV-2 genome 3
Rapid Antigen Tests (Including BinaxNOW)
- BinaxNOW tests detect viral nucleocapsid (N) protein rather than genetic material 1
- These tests provide results within 15 minutes, making them useful for point-of-care settings 1, 2
- BinaxNOW has high specificity (>99%) but lower sensitivity compared to PCR tests, particularly in asymptomatic individuals 2, 4
- Sensitivity is highest in symptomatic individuals within 7 days of symptom onset (87-96.5%) 2
Performance Characteristics of BinaxNOW
Sensitivity Based on Clinical Status
- In symptomatic adults within 7 days of symptoms: 87-96.5% sensitivity 2
- In symptomatic children within 7 days of symptoms: 84.6% sensitivity 2
- In asymptomatic adults: 70.2% sensitivity 2
- In asymptomatic children: 65.4% sensitivity 2
Correlation with Viral Load
- BinaxNOW sensitivity correlates strongly with viral load (as measured by PCR cycle threshold values) 2, 5
- 99.3% sensitivity for samples with CT values ≤25 2
- 95.8% sensitivity for samples with CT values ≤30 2
- 81.2% sensitivity for samples with CT values ≤35 2
Clinical Applications and Limitations
Advantages of BinaxNOW
- Rapid results (15 minutes) allow for immediate isolation decisions 1
- High throughput capability - a skilled operator can perform about 20 tests per hour 2
- Excellent interoperator agreement (100% in one study), indicating reliability 2
- Useful as an entry point for COVID-19 treatment in community settings 6
Limitations
- Lower sensitivity compared to PCR, especially in asymptomatic individuals 1, 5
- Temperature sensitivity - performance decreases when used outside recommended temperature range 2
- May miss infections with lower viral loads (higher CT values) 2, 5
Practical Considerations
- BinaxNOW can be used as a screening tool, but negative results in symptomatic individuals may need PCR confirmation 2
- Performance has been consistent across different Omicron subvariants 6
- In settings where rapid results are needed, BinaxNOW can be valuable despite lower sensitivity than PCR 4
Remember that while BinaxNOW provides rapid results, its lower sensitivity compared to PCR means that negative results should be interpreted with caution, particularly in high-risk settings or in symptomatic individuals with strong clinical suspicion for COVID-19.