Zhang 2013.

Study characteristics
Methods	Design: randomised controlled trial (assumed parallel assignment; unconfirmed) Duration: 60 days (8.7 weeks) Conducted in China
Participants	Population: 60 participants randomised to azithromycin (n = 30) or placebo (n = 30) Baseline characteristics % male: not reported Mean age: not reported % on maintenance ICS: not reported % on maintenance LABA/ICS: not reported Mean % predicted FEV1: not reported Mean daily ICS dose, µg: not reported Chlamydophila infection: not reported Inclusion criteria: we were unable to detail the specific inclusion and exclusion criteria for this trial because it was included from an existing systematic review (Tong 2015). The inclusion criteria of the review required that the study be designed to evaluate the "efficacy of prolonged treatment with macrolide antibiotics in adult patients with asthma". Exclusion criteria: not reported
Interventions	Run‐in: unknown Intervention: azithromycin 100 mg once daily Control: placebo
Outcomes	Trough FEV1
Notes	Funding: unknown Study ID(s): unknown
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Tong 2015 awarded 2 points for this domain, suggesting well‐reported and acceptable methods of random sequence generation.
Allocation concealment (selection bias)	Unclear risk	Information was not available.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Tong 2015 noted that methods of blinding were not adequately described in the study, although a placebo control was used.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Tong 2015 noted that methods of blinding were not adequately described in the study.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Tong 2015 noted that withdrawals and dropouts were not adequately described in the study.
Selective reporting (reporting bias)	Unclear risk	Information was not available.
Other bias	Unclear risk	Information was not available.

ACQ: Asthma Control Questionnaire; ACT: Asthma Control Test; ACTH; adrenocorticotropic hormone; ALT: alanine aminotransferase; AQLQ: Asthma Quality of Life Questionnaire; AST: aspartate aminotransferase;ATS: American Thoracic Society; CFC: chlorofluorocarbon; CPAP: continuous positive airway pressure; DRS: dose–response slope; ECG: electrocardiography;ECP: eosinophil cationic protein; ED: emergency department; FDA: Food and Drug Administration (USA); FeNO: fractional exhaled nitric oxide; FEV₁: forced expiratory volume in one second; FVC: forced vital capacity; GINA: Global Initiative for Asthma;ICS: inhaled corticosteroid;IgA: immunoglobulin A; IgE: immunoglobulin E; IgG: immunoglobulin G; IL‐8: interleukin‐8; IQR: interquartile range; ITT: intention‐to‐treat; LABA: long‐acting beta₂‐agonist; LCQ: Leicester Cough Questionnaire; LRTI: lower respiratory tract infection; n: number of participants; NIH: National Institutes of Health (USA) MCID: minimal clinically important difference; MDI: metred dose inhaler; OCS: oral corticosteroid; PC₂₀ or PD₂₀: provocative concentration (or dose) causing a 20% fall in forced expiratory volume in 1 second (FEV₁); Log PC₂₀: logarithm to the base 10 of PC₂₀; PCR: polymerase chain reaction; PEF: peak expiratory flow; PBRN: practice‐based research network; QT interval: measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle; SD: standard deviation; ULN: upper limit normal; URTI: upper respiratory tract infection.