You will be provided with the titles and abstracts of a collection of medical RCT reports studying a clinical question -- for instance, the efficacy of an intervention on some medical outcome. Please write a few sentences synthesizing the findings of these reports, which could serve as a conclusion section for a systematic review article. Your response should not include any other text. The RCT reports are below.



Title 1:
Randomized double-blind controlled trial of roxithromycin for prevention of abdominal aortic aneurysm expansion.
Abstract 1:
Macrolide treatment has been reported to lower the risk of recurrent ischaemic heart disease. The influence of macrolides on the expansion rate of abdominal aortic aneurysms (AAAs) remains unknown. The aim was to investigate the effect of roxithromycin on the expansion rate of small AAAs.
                A total of 92 subjects with a small AAA were recruited from two populations. One population consisted of 6339 men aged 65-73 years who were offered a hospital-based mass screening programme for AAA. From this population 66 subjects were recruited. The remaining 26 men were recruited from among 49 subjects diagnosed at interval screening for an initial aortic diameter between 25 and 29 mm. Subjects were randomized to receive either oral roxithromycin 300 mg once daily for 28 days or matching placebo, and followed for a mean of 1.5 years.
                During the first year the mean annual expansion rate of AAAs was reduced by 44 [corrected] per cent in the intervention group (1.56 mm per year), compared with 2.80 mm per year following placebo (P = 0.02). During the second year the difference was only 5 per cent [corrected]. Multiple linear regression analysis showed that roxithromycin treatment and initial AAA size were significantly related to AAA expansion when adjusted for smoking, diastolic blood pressure and immunoglobulin A level of 20 or more [corrected]. Logistic regression analysis confirmed a significant difference in expansion rates above 2 mm annually between the intervention and placebo groups: odds ratio = 0.09 (95 per cent confidence interval 0.01-0.83) [corrected].
                In comparison to placebo, roxithromycin 300 mg daily for 4 weeks reduced the expansion rate of AAAs.


Title 2:
Impaired results of a randomised double blinded clinical trial of propranolol versus placebo on the expansion rate of small abdominal aortic aneurysms.
Abstract 2:
To study the propranolol treatment of small abdominal aortic aneurysms (AAA) concerning intention to treat, side effects, and inhibition of expansion.
                
                Two-year lasting prospective randomised double-blinded intervention trial.
                Hospital-based mass screening for AAA with annual ambulatory control of small AAA.
                Of 122 screening-diagnosed small AAA, 51 (42%) were excluded because of contraindications or present beta-blockage, and 17 refused participation. Thus, 54 (44.3%) were included.
                Participants were randomised to 40 mg propranolol twice a day or placebo.
                The same observed was used to follow-up AAA-expansion, side effects, quality of life (QL), branchial and ankle blood pressure (ABI), and pulmonary function (FEV1 and FVC).
                Sixty percent in the propranolol group, and 25% in the placebo group dropped out, mainly caused by dyspnoea in the propranolol group (RR=1.74, 95% C.I.: 1.06-2.86). Five (16.7%) died in the propranolol group, while 1 (4.2%) died in the placebo group (RR=1.6 (1.02-2.51)). Furthermore, decreased pulmonary function, ABI, and QL was noticed in the propranolol group. Consequently, the trial was stopped after two years. Ninety-five percent of the measurements of the AAA were measured within 2 mm variation. If expansion was defined as above 2 mm annually, the relative risk of expansion in the placebo group was 1.17 (0.74-1.85), and 2.44 (0.88-6.77) among the non-drop-outs.
                Only 22% of small screenings-diagnosed AAA were treatable with propranolol for two years. Consequently, only large scale studies are capable of showing potential minor inhibition of expansion by propranolol. However, whether such treatment ever becomes ethically acceptable is debatable.


Title 3:
Use of doxycycline to decrease the growth rate of abdominal aortic aneurysms: a randomized, double-blind, placebo-controlled pilot study.
Abstract 3:
Eradication of Chlamydia pneumoniae infection and inhibition of elastolytic matrix metalloproteinases with doxycycline have been suggested to reduce the growth rates of small abdominal aortic aneurysms (AAA). We designed a study to investigate the efficacy of doxycycline in reducing the expansion of small AAAs.
                This was a prospective, double-blind, randomized, placebo-controlled study that was set in a university referral hospital. The study group consisted of 32 of 34 initially eligible patients who had an AAA diameter perpendicular to the aortic axis of 30 mm or more in size or a ratio of infrarenal to suprarenal aortic diameter of 1.2 or more and a diameter less than 55 mm. Patients were randomly assigned to receive either doxycycline (150 mg daily) or placebo during a 3-month period and underwent ultrasound surveillance during an 18-month period. Outcome measures included aneurysm expansion rates, the number of patients who had AAA rupture or repair, C pneumoniae antibody titers, and serum concentrations of C-reactive protein.
                The aneurysm expansion rate in the doxycycline group was significantly lower than that in the placebo group during the 6- to 12-month (P = .01) and the 12- to 18-month periods (P =.01). Five patients (41%) in the placebo group and 1 patient (7%) in the doxycycline group had an overall expansion of the aneurysm of 5 mm or more during the 18-month follow-up. Among the placebo group patients, a higher expansion rate was observed in those with enhanced C pneumoniae immunoglobulin G antibody titers (> 128) than in those with lower titers (P = .03). Doxycycline treatment had no clear effect on antibody titers. However, at 6-month follow-up, C-reactive protein levels in the doxycycline group were significantly lower than the baseline levels (P = .01).
                The results of this small pilot study suggest that doxycycline may favorably alter the outcome of patients with small AAA. However, because of the small size of this randomized study and of the potentially confounding effect of pretreatment risk factors, doxycycline-based treatment cannot be justified only on the ground of the current results. Because of the high prevalence of this disorder and its clinical, social, and economic relevance, a multicenter study should be performed to further investigate whether there is any place for medical treatment of small AAAs.


Title 4:
The effect of azithromycin and Chlamydophilia pneumonia infection on expansion of small abdominal aortic aneurysms--a prospective randomized double-blind trial.
Abstract 4:
The aim of the study was to evaluate the effect of azithromycin on the expansion rate of small abdominal aortic aneurysms (AAAs), and to determine whether or not a correlation exists between serological markers for Chlamydophilia pneumonia (Cpn) infection and AAA expansion.
                Nine vascular centers were included and 259 patients were invited to participate. Ten patients declined and 2 patients had chronic kidney failure, leaving a total of 247 patients. Inclusion criteria were: AAA 35-49 mm and age <80 years. Patients were randomized to receive either azithromycin (Azithromax, Pfizer Inc, New York, NY) 600 mg once daily for 3 days and then 600 mg once weekly for 15 weeks, or placebo in identical tablets. The ultrasound scans were performed in a standardized way within a month before inclusion and every 6 months for a minimum follow-up time of 18 months. Cpn serology was analyzed in blood samples taken at inclusion and 6 months later. Serum was analyzed for Cpn IgA and IgG antibodies by microimmunofluorescence (MIF). Computed tomography (CT) scans were done in 66 patients at inclusion and at 1 year for volume calculations.
                Thirty-four patients were excluded, ie, could not be followed for 18 months, 20 in the placebo group and 16 in the active treatment group. A total of 211 patients had at least two measurements and all were analyzed in an intention-to-treat analysis. Detectable IgA against Cpn was found in 115 patients and detectable IgG against Cpn in 160 patients. No statistically significant differences were found between the groups regarding median expansion rate measured by ultrasound scan (0.22 cm/year, interquartile range [IQR]: 0.09 to 0.34 in the placebo group vs 0.22, IQR: 0.12 to 0.36 in the treatment group, P = .85). Volume calculation did not change that outcome (10.4 cm(3)/year in the placebo group vs 15.9 cm(3)/year in the treatment group, P = .61). No correlation was found between serological markers for Cpn infection and the expansion rate. Patients taking statins in combination with acetylsalicylic acid (ASA) had significantly reduced expansion rate compared to patients who did not take statins or ASA, 0.14 cm/year vs 0.27 cm/year, P < .001.
                Azithromycin did not have any effect on AAA expansion. No correlation was found between serological markers for Cpn and AAA expansion, indicating no clinical relevance for Cpn testing in AAA surveillance. However, a significant reduction in AAA expansion rate was found in patients treated with a combination of ASA and statins.


Title 5:
Intermittent roxithromycin for preventing progression of small abdominal aortic aneurysms: long-term results of a small clinical trial.
Abstract 5:
Antibodies against Chlamydia pneumoniae are associated with an increased rate of expansion of small abdominal aortic aneurysms (AAAs). Short-term follow-up trials have shown a transient reduction AAA growth rate, in macrolide treated compared with placebo. Therefore we analysed the influence of intermittent, long-term roxithromycin treatment on AAA expansion and referral for surgery.
                Eighty-four patients with small AAAs were randomized to either an annual 4 weeks' treatment with roxithromycin or placebo, and followed prospectively.
                Intermittent, long-term Roxithromycin-treatment reduced mean annual growth rate by 36% compared with placebo after adjustment for potential confounders. Long-term roxithromycin-treated patients had a 29% lower risk of being referred for surgical evaluation, increasing to 57% after adjusting for potential confounders.
                Annual 4 week treatment with 300 mg roxithromycin daily may reduce the progression of small AAAs, and later need for surgical repair. However, more robust studies are needed for confirmation.
There is some limited evidence that antibiotic medication may have a slight protective effect in retarding the expansion rates of small AAAs. The quality of the evidence makes it unclear whether this translates into fewer referrals to AAA surgery, owing mainly to the small sample sizes of the studies.
Antibiotics were generally well tolerated with minimal adverse effects. Propranolol was poorly tolerated by patients in all of the beta-blocker trials and demonstrated only minimal and non-significant protective effects. Further research on beta-blockers for AAA needs to consider the use of drugs other than propranolol.
In general, there is surprisingly little high quality evidence on medical treatment for small AAAs, especially in relation to the use of newer beta-blockers, ACE inhibitors and statins.