Table 1
Definition and Data Source for Probabilities
| Term | Explanation | Data Source |
|---|---|---|
| P(RTI) | Probability of a person consulting with RTI in a 30-day period | From RTI consultation rate per 30 days in CPRD |
| P(AB|RTI) | Probability of receiving an AB prescription on the same date as an RTI consultation | From proportion of RTI consultations with AB prescribed, from CPRD |
| P(PTA) | Probability of PTA, per 30 days | From incidence of PTA in CPRD |
| P(RTI|PTA) | Probability of patients with PTA having consulted for an RTI in the 30 days preceding their PTA diagnosis | Proportion of PTA cases with previous RTI consultation, calculated from CPRD |
| P(PTA|RTI) | Probability of PTA arising in the 30 days following an RTI consultation |
 |
| P(PTA|[AB|RTI]) | Probability of patients with PTA having consulted for an RTI and received AB prescription |
 |
| P(PTA|[No AB|RTI]) | Probability of patients with PTA having consulted for an RTI and not received an AB prescription |
 |
| NNT | The number of additional antibiotic prescriptions required to prevent 1 case of PTA |
 |
AB = antibiotic; CPRD = Clinical Practice Research Datalink; NNT = number needed to treat; P = probability; PTA = peritonsillar abscess; RTI = respiratory tract infection.