COVID-19 Management

2022 Cochrane Update: How Reliable are COVID-19 Rapid Tests?

BACKGROUND AND PURPOSE:

Dinnes et al. (Cochrane Database of Systematic Reviews, 2022) update a 2021 review and meta-analysis investigating the diagnostic accuracy of rapid, point-of-care SARS-CoV-2 antigen tests

Systematic review and meta-analysis
Inclusion criteria
- Studies of people with either suspected SARS-CoV-2 infection, known infection or known absence of infection
- Test accuracy studies of any design that evaluated commercially produced, rapid antigen tests
- Evaluations of single applications of a test (one test result reported per person) and evaluations of serial testing (repeated antigen testing over time)
Study design
- Controls for infection status were any laboratory-based molecular test (primarily RT-PCR) or pre-pandemic respiratory sample
- Data pooling and quality assessment were performed
- Random-effects logistic regression models were used
Primary outcome
- Sensitivity and specificity of each test

155 cohort studies | 100,462 unique samples in main results
- Commercial antigen assays evaluated: 49
- Risk of bias in included studies was high

Rapid Test Sensitivity and Specificity

Test sensitivity was higher in symptomatic vs asymptomatic individuals
- Symptomatic
  - Mean sensitivity: 73.0% (95% CI, 69.3 to 76.4)
  - 109 evaluations | 50,574 samples | 11,662 cases
- Asymptomatic
  - Mean sensitivity: 54.7% (95% CI, 47.7 to 61.6)
  - 50 evaluations | 40,956 samples | 2641 cases
Test sensitivity was also higher in the first week after symptom onset
- First week after symptom onset
  - Mean sensitivity: 80.9% (95% CI, 76.9 to 84.4)
  - 30 evaluations | 2408 cases
- Second week after symptom onset
  - Mean sensitivity: 53.8% (95% CI, 48.0 to 59.6)
  - 40 evaluations | 1119 cases
For those who were asymptomatic at the time of testing, sensitivity was higher when exposure to SARS-CoV-2 was suspected
- Suspected exposure
  - Mean sensitivity: 64.3% (95% CI, 54.6 to 73.0)
  - 16 evaluations | 7677 samples | 703 cases
- Widely available COVID-19 testing for anyone
  - Mean sensitivity: 49.6% (95% CI, 42.1 to 57.1)
  - 26 evaluations | 31,904 samples | 1758 cases
Mean test specificity was similarly high for both symptomatic and asymptomatic participants
- Symptomatic: 99.1%
- Asymptomatic: 99.7%
There was a decline in sensitivities as sample viral load decreased

Sensitivity Varies Widely Between Test Brands

For symptomatic participants
- Number of assays with sensitivity meeting WHO performance criterion of ≥80%: 7 assays
- Number of assays with specificity meeting WHO performance criterion of ≥97%: 17 assays | 12 of demonstrated specificities >99%
Performance range among symptomatic individuals
- Mean sensitivity 34.3% to 91.3%
Performance range among asymptomatic individuals
- Mean sensitivity 28.6% to 77.8%

Modeled Positive Predictive Value of Rapid Tests

At 5% prevalence: Using summary data in symptomatic people during the first week after symptom onset, the positive predictive value (PPV) of rapid testing was 89%
- Predicted false positives: 1 in 10 positive tests
- Predicted missed cases: 1 in 5 cases
At 0.5% prevalence: Using summary data for asymptomatic people where exposure was suspected, PPV was between 38 and 52%
- Predicted false positives: between 2 in 5 and 1 in 2 positive tests
- Predicted missed cases: between 1 in 2 and 1 in 3 cases

Estimates of test sensitivity varied considerably between studies and test brand, but specificity was consistently high for most brands
Test sensitivity was highest when viral loads likely to be elevated
- In the first week of illness
- Among symptomatic individuals
- Among asymptomatic individuals who suspected COVID-19 exposure
Some tests, like those that met WHO test standards, were specific and sensitive enough to replace RT-PCR among symptomatic individuals, while others would be more suited to determining which individuals should receive follow-up RT-PCR testing

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