Table 1.

Precision of the cumulative incidence estimate assuming a sample size of 1450 participants, by three levels of magnitude of the cumulative incidence hypothesized. Reported are the positive predictive values for the Roche Elecsys Anti-SARS-CoV-2 serum antibody test according to 100% sensitivity and 99.8% specificity declared by the manufacturer

Hypothesized cumulative incidence	Confidence interval of the estimated cumulative incidence	Confidence level	Positive predictive value of the test (confidence interval)
0.440%	0.1%, 1.1%	99.0%	70% (33%, 85%)
0.088%	0.0%, 0.5%	98.2%	31% (0%, 72%)
0.066%	0.0%, 0.5%	98.9%	25% (0%, 72%)