Nine RCTs were included in the review with 3,685 participants.
The number needed to treat (NNT) was approximately 40.
Compared with response to increased steroids, in patients receiving salmeterol, morning peak expiratory flow was greater at three months (difference 22.4 (95% CI: 15.0, 30.0) litre/min, P < 0.001) and six months (27.7 (95% CI: 19.0, 36.4) litre/min, P < 0.001). There was no statistically significant heterogeneity.
Forced expiratory volume in one second (FEV1) was also increased at three months (0.10 (95% CI: 0.04, 0.16) litres, P < 0.001) and six months (0.08 (95% CI: 0.020, 014) litres, P < 0.01). There was no statistically significant heterogeneity.
Mean percentage of days and nights without symptoms (three months: days, 12% (95% CI: 9%, 15%), nights, 5% (95% CI: 3%, 7%); six months: days, 15% (95% CI: 12%, 18%), nights, 5% (95% CI: 3%, 7%); all P < 0.001. There was no statistically significant heterogeneity.
Mean percentage of days and nights without need for rescue treatment (three months: days, 17% (95% CI: 14%, 20%), nights, 9% (95% CI: 7%,11%); six months: days, 20% (95% CI: 17%, 23%), nights, 8% (95% CI: 6%, 11%); all P < 0.001.
Fewer patients experienced any exacerbation with salmeterol (difference 2.73% (95% CI: 0.43%, 5.04%), P = 0.02), and the proportion of patients with moderate or severe exacerbations was also lower (2.42% (95% CI: 0.24%, 4.60%), P = 0.03).