Trial design
The present study is a two parallel randomized double-blinded, placebo-control trial group. We recruited only patients with chronic bronchitis due to sulfur mustard gas inhalation who referred to the pulmonary clinics affiliated with Foundation of Martyrs and Veterans Affairs, Shiraz, Iran. The study protocol was approved by the institutional review board (IRB) of Shiraz University of Medical Sciences as well as the local ethics committee. After explaining the study objectives, all the participants gave their written informed consent. The trial was registered with the Iranian Clinical Trials Registry (IRCT138904144312N1; www.irct.ir).
Participants
Ninety men between the age of 45-75 years old diagnosed with chronic bronchitis due to mustard gas inhalation during the eight years Iran-Iraq war were consecutively recruited from the outpatient clinic (chronic bronchitis characterized by a cough productive of sputum daily for over three months duration during two consecutive years and airflow obstruction). Exclusion criteria included a history of exacerbation of symptoms within the past 4 weeks, connective tissue disease, sarcoidosis, eosinophilic granuloma, pneumoconiosis, lymphoma, carcinomatous, active tuberculosis, chronic liver disease, and currently taking statins or those who used it within the last 3 months prior to the study. In addition, those who smoked or were former smokers, who had stopped smoking less than 1 year were also excluded from the study.
Interventions & outcomes
The patients were randomly assigned to receive either atorvastatin (40 mg) or placebo (starch pills, made by Shiraz Pharmacology School, Iran), given orally once a day for 3 months. The shape and packing of both pills was similar, so patients and the researches were blinded to the treatment group allocation.
Demographic data; including age, body mass index (BMI), heart rate, respiratory rate, systolic and diastolic blood pressure, and drug history of each patient was recorded in a date sheet. In addition, blood tests including total cholesterol, triglyceride (TG), liver-function tests (LFTs), hemoglobin (Hb), and spirometry were recorded at the baseline. The primary outcome of this study was to assess systemic inflammation status at 3 months compared with baseline, measured by white blood cell (WBC) count, interleukin 6 level (IL-6), and tumor necrosis factor α (TNF-α). Also, we considered COPD assessment test (CAT) as the secondary outcomes. CAT is a patient-completed instrument to assess and quantify health-related quality of life and symptom burden in patients with COPD. It comprises of 8 questions, and each present a semantic 6-point (0-5) differential scale, providing a total score out of 40. The higher scores exhibit the severity of COPD impact on a patient’s life. (22).
Measurements
All assessments were performed at baseline and the end of intervention. The IL-6 and TNF-α, concentrations were measured with enzyme linked immunosorbent assay (ELISA) commercial kits (Platinum, Austria) according to the manufacturer’s instructions. The reference range of IL-6 and TNF-α serum level were considered 1.8 pg/ml and up to 2.8 pg/ml. The high sensitive CRP concentration was measured with enzyme linked immunosorbent assay (ELISA) commercial kits (Diagnostics Biochem Canada Inc., Canada) according to the instructions of manufacturer. The serum level of high sensitive CRP less than 10 mg/l was considered as normal. The procalcitonin (PCT) level was measured via an automatic analyzer, the VIDAS® B.R.A.H.M.S PCT assay (bioMérieux, Marcy L'Etoile, France). The reference range of PCT was less than 150 pg/ml. BMI was calculated, using the weight and height measurements. Blood pressure was measured after a 5-min resting period with the individual sitting in a chair and determined, using a standard mercury sphygmomanometer. Moreover, the total CAT score was calculated for each patient by summing the points for each variable.
Randomization
Randomization sequence was created, using random block sizes of 4 and 6. On the order of referral, the participants were allocated 1:1 into two groups. Study pills were allocated in separate packs blinded and labeled, using a four-digit code. The information regarding which codes correspond to what treatment was maintained secret by the project coordinator. The patients, attending physicians, staff involved in the pulmonary clinics, and members collecting and analyzing data were all blinded to the intervention allocation.
Statistical Analysis
All statistical analyses were performed with the Statistical Package for Social Sciences version 19.0 (SPSS Inc., Chicago, IL, USA). We estimated that a total of 90 participants required to detect significant difference between the groups, with a two-tailed α of 0.05 and a (1-β) of 0.80, for a comparison of 2 independent mean of outcome with effect size of 0.6. The Kolmogorov-Smirnov test was used to test normality of variables’ distribution. The baseline characteristics of both groups were compared, using X2 tests or Fisher’s exact test for proportions. For continuous variables, independent groups were compared, using the t-test or Mann-Whitney test, whereas paired comparison was made, using paired t-test or Wilcoxon test. Data are reported as means ± SD. A two-sided P value less than 0.05 was considered to be statistically significant. The effect size and 95% confidence interval of effect size of variables were calculated, using online calculators(23, 24).