Key characteristics of message wording from each country; full wording in online supplemental information
| Short title | Original source* | Word count | Communicates possibility of false positive? | Communicates possibility of false negative? |
| US wording | US Centers for Disease Control and Prevention | 225 | No | Indirectly (‘you probably were not infected at the time your sample was collected’, with further caveat implying that you could be infected now even if you were not infected when the sample was taken) |
| New Zealand wording | New Zealand Ministry of Health | 548 | Indirectly, as a remote possibility (‘We expect very few (if any) false positive test results (a false positive being a positive test result for someone who does not have the disease’) | Yes (paragraph about reasons why false negatives are possible) |
| UK wording | UK National Health Service | 443 | No | No |
| Experimental wording | UK National Health Service (modified by researchers) | 613 | Indirectly, as a remote possibility (‘A positive result means you almost certainly had coronavirus when the test was done’) | Yes (paragraph about reasons why false negatives are possible) |
*Wording retrieved from original sources in September 2020.