Are [[beta].sub.2]-agonists effective treatment for acute bronchitis or acute cough in patients without underlying pulmonary disease? A systematic review - Original Research

Journal of Family Practice, Nov, 2001 by John J. Smucny, Cheryl A. Flynn, Lorne A. Becker, Richard H. Glazier

Two investigators (C.F., J.S.) independently reviewed all the retrieved titles and abstracts. Studies selected by either investigator as possibly meeting the inclusion criteria were retrieved in their entirety. One investigator (J.S.) then deleted the journal of publication, title, authors, affiliations, and results sections of each study that met the inclusion criteria, and compiled a list of all the reported outcomes. The list of outcomes was forwarded to the other 3 investigators who independently, and then through discussion, determined which outcomes would be included in our review. The main criterion for selection was that the outcome should be directly important to patients. The same 3 investigators then graded the quality of each study using the 5-point Jadad scale, with points given for method of randomization (0-2), adequacy of blinding (0-2), and description of withdrawals (0-1). (18) The Jadad scale is a validated, well-accepted, and frequently used quality assessment scale. Agreement on quality was assessed with a [kappa] score, and disagreements were resolved by discussion. Trials were excluded if all investigators agreed that the trial did not meet our inclusion criteria. The remaining articles in their entirety were then distributed to all investigators, each of whom independently extracted data for the selected outcomes. Disagreements were resolved by discussion. We attempted to contact authors to obtain missing data.

Summary statistics were calculated using Review Manager 4.1 software (Update Software, Oxford, England). We used fixed effects models for outcomes without statistically significant heterogeneity (at P <.10) and random effects models for outcomes with significant heterogeneity. For dichotomous outcomes, we reported relative risks (RRs), absolute risk reductions, and numbers needed to treat (NNTs), and for continuous outcomes, standardized mean differences (SMD). We considered a level of P less than .05 to be statistically significant.

RESULTS

Included Studies

The major characteristics of the trials are shown in Table 1. We included 6 controlled trials comparing [[beta].sub.2]-agonists and placebo, (19-24) and one trial comparing a [[beta].sub.2]-agonist with erythromycin. (25) A trial comparing a [[beta].sub.2]-agonist with placebo in children (26) was excluded because all participants had recurrent cough and the mean duration of cough (8 weeks) was much longer than the maximum of 30 days used in the other trials.

All trials enrolled patients that presented to primary care settings. The stated diagnoses were "acute bronchitis," (21,22,25) "acute cough," (19,20) and "acute transient cough." (23,24) Both trials in children excluded participants with abnormal lung examinations (19) or "with bronchial obstruction needing bronchodilating medication." (23) None of the adult trials excluded patients with wheezing; the percentage with wheezing ranged from 20% to 44% in the 4 trials that mentioned it. All adult trials included both smokers and nonsmokers.