Summary of subject characteristics of included studies
| Trial |
Mean (SD or range) age (years) |
Asthma diagnosis | Severity of asthma | Concurrent medication | Severity of gastro-oesophageal reflux | Symptomatic gastrooesophageal reflux (%) | Association between gastro-oesophageal reflux and asthma reported |
| Ekstrom19 | 58.5 (28–70) | ATS | Moderate or severe | 20/48 OCS; antacids allowed | Symptoms of heartburn and/or acid regurgitation 48/48; abnormal pH 32/48 | 100% | Yes (27/50) |
| Ford20 | 63 (50–80) | DR | Baseline PEF 253–300 l/min | ICS 8/10; antacids allowed | Oesophagitis: grade I (n=1); grade II (n=1); grade III (n=3); Barrett's oesophagus (n=2) | 100% | No |
| Goodall21 | 54 (30–65) | DR | Nocturnal wheezing, improvement in FEV1>20% in 11/20 subjects | ICS or OCS 15/16 | Oesophagitis 11/20; abnormal pH 8/18; decreased LESP 8/20; heartburn 19/20; regurgitation 12/20 | 95% | Yes (10/18) |
| Gustaffson 22 | 14.2 (10–20) | DR | Not stated | SCG 23/37; ICS 12/37; Iβ2A 19/37; Oral Theo 25/37; OCS 2/37 | Mean (SE) % time pH <4 = 0.5 (0.1); 2.7 (0.3) | 49% | No |
| Kjellen23 | 52 (36–65) | ATS | Described as more severe asthma | Iβ2A 52/61; ICS 18/61; OCS 13/61; Theo 8/61 | Hiatial hernia 55%; dysmotility 58%; abnormal pH 35%; decreased LESP 40% | Not reported | No |
| Larrain24 | 44 (11) | DR | 56/81 reactive airways | Antacids allowed; OCS or ICS 38/90; Theo: number not specified | Oesophagitis: grade 1 (n=20/81); normal (n=60/81). Free reflux on radiography after loading stomach with 300 ml acid (n=38/81) | 74% | No |
| Meier25 | 49 (34–63) | ATS | Not reported; inclusion criteria required >15% reversibility (FEV1 and PEF) | Asthma medications continued as usual; type of medications not specified | Oesophagitis 15/15: grade I (n=1); grade II (n=4); grade III (n= 8); grade IV (n=2); stricture (n=8/15); Barrett's oesophaus (n=2/15); hiatal hernia (n=10/15) | 100% | Yes (proportion not reported) |
| Nagel26 | 42 (20–64) | DR | Not reported; inclusion criteria required >25% reversibility (FEV1 and PEF) | Usual medications continued; type not specified | Abnormal 24 hour pH monitoring | 100% | Yes (15/15) |
| Teichtahl27 | 46 (12) | DR | Not reported; inclusion criteria required >15% reversibility (FEV1) and diurnal variation of PEF of ⩾20% in PEF in past 6 months | SCG and Oβ2A not allowed; Iβ2A allowed as required; other asthma medications continued as usual | Grade 0 (n=3); grade I (n=4); grade II (n=11); grade III (n=2). Mean % of time pH <4 = 12.2% | 95% | No |
| Boeree28 | 51 (10) | ATS | Moderate to severe | ICS >0.4 mg/day | Mild symptoms, abnormal pH in all | 50% | No |
| Levin29 | 57 (35–72) | ATS | Not stated | Iβ2A in all | Abnormal pH in all | 100% | No |
| Kiljander30 | 49 (21–75) | ATS | Mild to moderate | Iβ2A 91%; ICS 89% | Abnormal pH in all | 65% | No |
ATS = diagnosis for asthma made in accordance with American Thoracic Society guidelines; DR = asthma diagnosis made in accordance with a doctor's diagnosis; LESP = lower oesophageal sphincter pressure; SCG = sodium cromoglycate; ICS=inhaled corticosteroids; OCS= oral corticosteroids; Iβ2A = inhaled β2agonists; Oβ2A = oral β2 agonists; Theo = theophylline; PEF = peak expiratory flow.