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. 2022 Nov 10;12(11):e063271. doi: 10.1136/bmjopen-2022-063271

Figure 1.

Figure 1

Graphical illustrations of potential study scenarios with test negative controls. Example (A): Positive SARS-CoV-2 RT-PCR case. Individual (A) is followed up from 14 days after SARS-CoV-2 infection for 12 months. Examples (B–D): Test negative controls. Individual (B) is matched to an individual with SARS-CoV-2 infection and followed up from 14 days after matching for 12 months. Individual (C) is matched to an individual with SARS-CoV-2 infection and followed up from 14 days after matching until they are first recorded with SARS-CoV-2 infection themselves during the RT-PCR testing period of interest. At this point, they are censored from further follow-up as a test negative comparator and followed up as an exposed case from 14 days after infection for 12 months with appropriate matches for the date of positive RT-PCR. Individual (D) is matched to an individual with SARS-CoV-2 infection and followed up from 14 days after matching until they are first recorded with SARS-CoV-2 infection themselves. As this occurs after the RT-PCR testing period of interest, they are censored from further follow-up as an unexposed comparator. GP, general practitioner; RT-PCR, reverse transcription PCR.