Table 1 Baseline information on original studies included in the meta-analysis.

Sugiura et al 2003 [7]

NR

Randomized, placebo-controlled parallel design.

FEV₁/FVC < 0.7; all patients wereex-smokers who had stopped smoking for at least 1 year beforethe study.

A history of perennial allergic rhinitis; positiveallergen skin prick tests and RAST assay; a history of periodicwheezing; an improvement in FEV₁ of more than 12 % predicted oran absolute increase of 200 ml after inhalation of 200 μg salbutamol; had bronchial or respiratory tract infectionsin the month preceding the study; had taken systemic steroids in the 2 monthsbefore the study or inhaled steroids in the month beforethe study.

NR

None

NR

Keatings et al 1997 [18]

Outpatient clinics in different hospitals

Randomized, single-blind, crossover design with 3–7 day run in period. The clinical part of the study was single-blind, but all differential cell counting and assayswere carried out in a double blind fashion.

FEV₁/FVC < 0.7; FEV₁ < 70% predicted; reversibility with inhaled albuterol of <10% of predicted FEV₁; smoking history of at least 10 pack-years; negative results on skin prick testing to four common aeroallergens.

Patients who had taken inhaled or oral steroids or who had suffered an exacerbation of their airway disease in the previous 6 weeks, or patients with any history of asthma or variability in symptoms were excluded.

Albuterol was allowed.

2 subjects

NR

Culpitt et al 1999 [19]

Outpatient clinic

Randomized, double-blind, placebo-controlled crossover design with a run-in period of 2 weeks.

FEV₁/FVC < 0.7; postbronchodilat or FEV₁ <85% predicted; reversibility with inhaled β₂-agonist of <15% of predicted FEV₁; smoking history of at least 20 pack-years.

Patients who had taken inhaled or oral steroids or who had suffered an exacerbation of their airway disease in the previous 6 weeks, or patients with any history of asthma or atopy or variability in symptoms were excluded.

Three subjects had concomitant treatment with albuterol (200 μg twice a day) and ipratropium bromide (40 μg twice a day), one subject with albuterol (200 μg as needed) alone.

12 subjects

Samples were considered adequate for analysis if there was < 50% squamous cell contamination.

Confalonieri 1998 [20]

Outpatient clinic

Randomised, controlled, open study. The clinical parts of the study was open, but all differential cell counting was carried out in a double blind fashion.

FEV₁/FVC <88% of predicted in men and <89% in women; all patients were current smokers.

Patients who had taken inhaled or oral steroids or had suffered a respiratory tract infection in the previous three months were excluded.

None of the patients was taking theophyllines or long acting β₂ agonists.

None

Samples were discarded if viability levels were 50% or less, or squamous contamination was 20% or more. An overall differential cell count on 500 nucleated non-squamous cells was performed by two examiners and results reported as mean of the two counts.

Mirici et al 2001 [21]

Outpatient clinic

Randomized, double-blind, placebo-controlled parallel design.

FEV₁ < 70% predicted; no self-reported asthma; reversibility with inhaled terbutaline of <15% of predicted FEV₁; current smokers.

Long-term treatment with oral or inhaled steroids within 6 months of study entry; A respiratory tract infection in previous 3 months; pregnancy or lactation, or presence of other serious systemic diseases.

β₂ – agonists of all kinds, theophylline, and mucolytics were allowed.

10 subjects

Samples were discarded if viabilitylevels were 50% or less, or squamous contamination was 20% or more

Yildiz et al 2000 [22]

Outpatient clinic

Randomized, placebo-controlled parallel design with a run-in period of 2 weeks.

FEV₁/FVC < 0.7; FEV₁ < 70% predicted; reversibility with inhaled albuterol of <10% of predicted; smoking history of at least 10 pack-years.

Patients with any history of asthma or variability in symptoms, and patients who had taken inhaled or oral steroids or had suffered a respiratory tract infection or exacerbation in the previous 6 weeks were excluded.

All of the patients continued to inhale both salbutamol and ipatropium bromide. In 9 patients, sustained release theophylline was also administered.

None

NR