Williamson 1984.
| Methods | Double‐blinded RCT | |
| Participants | 74 adults (age 21 to 65 years) with cough and sputum, and concurrent upper respiratory tract infection, rhonchi, or history of fever; excluded if temperature more than 39.5° C, signs or symptoms of sinus infection, or chest radiograph with consolidation (but not ordered on all). Dropouts = 5/74 | |
| Interventions | Doxycycline (100 mg twice daily on day 1, then 100 mg 4 times a day on days 2 to 7) versus identical‐looking placebo. Kept daily symptom log, returned for follow‐up visit on day 7 to 10. If not improved at follow‐up, could obtain antibiotic prescription. | |
| Outcomes | General well‐being, bother of cough, night cough, activity limitation, feverishness, sputum colour daily, doses of antitussives, and clinical impression at follow‐up | |
| Notes | No mention of eligible patients who refused to volunteer | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | |
| Allocation concealment (selection bias) | Low risk | |
| Blinding (performance bias and detection bias) All outcomes | Low risk | |
| Blinding (performance bias and detection bias) | Low risk | |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | |
| Selective reporting (reporting bias) | Unclear risk | Not reported |
| Other bias | Unclear risk | Not reported |
FEV1: forced expiratory volume in one second LRTI: lower respiratory tract infection RCT: randomised controlled trial