Will a patient who tested positive for COVID-19 (Coronavirus Disease 2019) two weeks ago still test positive on an Abbott (rapid diagnostic test) test?

COVID-19 Testing After Two Weeks: Abbott Test Positivity

A patient who tested positive for COVID-19 two weeks ago is unlikely to still test positive on an Abbott rapid antigen test, though they may still test positive on PCR testing. 1, 2

Understanding Test Positivity Over Time

Antigen Tests vs. PCR Tests

• Antigen tests (like Abbott): Detect viral proteins and primarily identify active, infectious disease
• PCR tests: Detect viral RNA and can remain positive long after a person is no longer infectious

Timeline of Test Positivity

• First week of infection: Highest viral shedding occurs, with peak viral load typically around day 4 1
• After 1-2 weeks:
  • Viral load typically decreases significantly
  • Infectious virus is rarely isolated after 8 days of symptoms 1
  • PCR tests may remain positive for up to 30 days after infection, even when the person is no longer infectious 1

Abbott Rapid Antigen Test Specifics

The Abbott rapid antigen test specifically:

• Is designed to detect higher viral loads associated with active infection 1
• Has lower sensitivity compared to PCR tests, especially when viral loads are lower 3
• Is most accurate when used within 5 days of symptom onset 1
• Is unlikely to detect residual viral proteins two weeks after initial infection in most cases

Clinical Implications

For the Patient in Question

• At two weeks post-infection, the patient:
  • Is likely past their period of highest infectivity
  • May still test positive on PCR but is less likely to test positive on an Abbott rapid antigen test
  • Has likely developed antibodies to SARS-CoV-2 by this point 1

Important Considerations

• False negatives: Abbott tests have limited sensitivity in asymptomatic individuals or those with low viral loads 3
• Clinical context matters: If the patient has ongoing symptoms, test results should be interpreted with caution
• Rare recurrences: True COVID-19 recurrence is rare (approximately 4.3 cases per 10,000 COVID-19 patients) 4

Recommendations for Testing After COVID-19

The Infectious Diseases Society of America (IDSA) and other guidelines do not recommend routine repeat testing to document viral clearance 1, 2:

• For most patients: No need for repeat testing after completing isolation period
• For return to normal activities: Base on symptom resolution rather than negative test results
• Standard isolation period: Minimum 10 days from symptom onset, plus 24 hours fever-free and improvement in other symptoms 2

Common Pitfalls to Avoid

• Overreliance on test results: PCR positivity doesn't necessarily indicate infectiousness
• Premature testing: Testing too soon after infection can lead to unnecessary prolonged isolation
• Misinterpreting results: A negative antigen test two weeks after infection doesn't guarantee the person never had COVID-19
• Ignoring clinical context: Persistent or worsening symptoms should prompt clinical evaluation regardless of test results

In conclusion, while PCR tests may remain positive for extended periods, Abbott rapid antigen tests are much less likely to be positive two weeks after initial infection in most patients who have clinically recovered.