Tazobactam/piperacillin for moderate-to-severe pneumonia in patients with risk for aspiration: comparison with imipenem/cilastatin

Investigation of predictors for in-hospital death or long-term hospitalization in community-acquired pneumonia with risk factors for aspiration

Background

It is known that the mortality of pneumonia in patients with risk factors for aspiration is worse than that in those without these risk factors. However, it is still unknown which risk factors for aspiration predict prognosis. Therefore, we aimed to determine which risk factors for aspiration are associated with death or prolonged hospitalization.

Methods

We prospectively followed patients with community-acquired pneumonia at a single hospital providing acute to chronic care in Japan until they died or were discharged. Patients at any risk of aspiration were included. The associations between pneumonia severity, individual risk factors for aspiration, and in-hospital death or prolonged hospitalization were investigated. Overall survival was estimated by the Kaplan - Meier method, and the factors associated with in-hospital death or prolonged hospitalization were investigated by multivariate analysis using factors selected by a stepwise method.

Results

In total, 765 patients with pneumonia and risk factors for aspiration were recruited. One hundred and ten patients deceased, and 259 patients were hospitalized over 27 days. In-hospital death increased as the number of risk factors for aspiration increased. In the multivariate analysis, male, impaired consciousness, acidemia, elevated blood urea nitrogen, and bedridden status before the onset of pneumonia were associated with in-hospital death (odds ratio [OR]: 2.5, 2.5, 3.6, 3.1, and 2.6; 95% confidence interval [CI]: 1.6-4.1, 1.4-4.2, 1.6-8.0, 1.9-5.0, and 1.6-4.2 respectively). In the Cox regression analysis, these factors were also associated with in-hospital death. None of the vital signs at admission were associated. Tachycardia, elevated blood urea nitrogen, hyponatremia, and bedridden status were associated with hospitalization for >27 days (OR: 4.1, 2.3, 4.3, and 2.9; 95% CI: 1.3-12.9, 1.5-3.4, 2.0-9.4, and 2.0-4.0, respectively).

Conclusions

Blood sampling findings and bedridden status are useful for predicting in-hospital mortality and long-term hospitalization in patients with pneumonia and any risk factor for aspiration.

Protein C activity as a potential prognostic factor for nursing home-acquired pneumonia

Introduction

Despite the poor prognosis for nursing home acquired pneumonia (NHAP), a useful prognostic factor is lacking. We evaluated protein C (PC) activity as a predictor of in-hospital death in patients with NHAP and community-acquired pneumonia (CAP).

Methods

This prospective, observational study included all patients hospitalized with pneumonia between July 2007 and December 2012 in a single hospital. We measured PC activity at admission and investigated whether it was different between survivors and non-survivors. We also examined whether PC activity < 55% was a predictor for in-hospital death of pneumonia by logistic regression analysis with CURB-65 items (confusion, blood urea >20 mg/dL, respiratory rate >30/min, and blood pressure <90/60 mmHg, age >65). When it was a useful prognostic factor for pneumonia, we combined PC activity with the existing prognostic scores, the pneumonia severity index (PSI) and CURB-65, and analyzed its additional effect by comparing the areas under the receiver operating characteristic curves (AUCs) of the modified and original scores.

Results

Participants comprised 75 NHAP and 315 CAP patients. PC activity was lower among non-survivors than among survivors in NHAP and all-pneumonia (CAP+NHAP). PC activity <55% was a useful prognostic predictor for NHAP (Odds ratio 7.39 (95% CI; 1.59–34.38), and when PSI or CURB-65 was combined with PC activity, the AUC improved (from 0.712 to 0.820 for PSI, and 0.657 to 0.734 for CURB-65).

Conclusions

PC activity was useful for predicting in-hospital death of pneumonia, especially in NHAP, and became more useful when combined with the PSI or CURB-65.

Development and validation of a new scoring system for prognostic prediction of community-acquired pneumonia in older adults

The discriminative power of CURB-65 for mortality in community-acquired pneumonia (CAP) is suspected to decrease with age. However, a useful prognostic prediction model for older patients with CAP has not been established. This study aimed to develop and validate a new scoring system for predicting mortality in older patients with CAP. We recruited two prospective cohorts including patients aged ≥ 65 years and hospitalized with CAP. In the derivation (n = 872) and validation cohorts (n = 1,158), the average age was 82.0 and 80.6 years and the 30-day mortality rate was 7.6% (n = 66) and 7.4% (n = 86), respectively. A new scoring system was developed based on factors associated with 30-day mortality, identified by multivariate analysis in the derivation cohort. This scoring system named CHUBA comprised five variables: confusion, hypoxemia (SpO₂ ≤ 90% or PaO₂ ≤ 60 mmHg), blood urea nitrogen ≥ 30 mg/dL, bedridden state, and serum albumin level ≤ 3.0 g/dL. With regard to 30-day mortality, the area under the receiver operating characteristic curve for CURB-65 and CHUBA was 0.672 (95% confidence interval, 0.607–0.732) and 0.809 (95% confidence interval, 0.751–0.856; P < 0.001), respectively. The effectiveness of CHUBA was statistically confirmed in the external validation cohort. In conclusion, a simpler novel scoring system, CHUBA, was established for predicting mortality in older patients with CAP.

Trends in the incidence and outcome of sepsis using data from a Japanese nationwide medical claims database-the Japan Sepsis Alliance (JaSA) study group

Background

Trends in the incidence and outcomes of sepsis using a Japanese nationwide database were investigated.

Methods

This was a retrospective cohort study. Adult patients, who had both presumed serious infections and acute organ dysfunction, between 2010 and 2017 were extracted using a combined method of administrative and electronic health record data from the Japanese nationwide medical claim database, which covered 71.5% of all acute care hospitals in 2017. Presumed serious infection was defined using blood culture test records and antibiotic administration. Acute organ dysfunction was defined using records of diagnosis according to the international statistical classification of diseases and related health problems, 10th revision, and records of organ support. The primary outcomes were the annual incidence of sepsis and death in sepsis per 1000 inpatients. The secondary outcomes were in-hospital mortality rate and length of hospital stay in patients with sepsis.

Results

The analyzed dataset included 50,490,128 adult inpatients admitted between 2010 and 2017. Of these, 2,043,073 (4.0%) patients had sepsis. During the 8-year period, the annual proportion of patients with sepsis across inpatients significantly increased (slope = + 0.30%/year, P < 0.0001), accounting for 4.9% of the total inpatients in 2017. The annual death rate of sepsis per 1000 inpatients significantly increased (slope = + 1.8/1000 inpatients year, P = 0.0001), accounting for 7.8 deaths per 1000 inpatients in 2017. The in-hospital mortality rate and median (interquartile range) length of hospital stay significantly decreased (P < 0.001) over the study period and were 18.3% and 27 (15–50) days in 2017, respectively.

Conclusions

The Japanese nationwide data indicate that the annual incidence of sepsis and death in inpatients with sepsis significantly increased; however, the annual mortality rates and length of hospital stay in patients with sepsis significantly decreased. The increasing incidence of sepsis and death in sepsis appear to be a significant and ongoing issue.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03762-8.

Risk factors associated with methicillin-resistant Staphylococcus aureus isolation from serially collected sputum samples of patients hospitalized with pneumonia

INTRODUCTION

Risk factors associated with the new detection of methicillin-resistant Staphylococcus aureus (MRSA) during hospitalization remain unclear. This study aimed to identify risk factors associated with MRSA isolation from the sputum of patients admitted with pneumonia, during their hospitalization.

METHODS

Patients were prospectively enrolled from 2003 to 2012. Sputum samples were collected for bacterial cultures on days 1, 4, 7, 11, and 14 of hospitalization and thereafter. Cases of MRSA first isolated from sputum obtained before day 4 were defined as "carriage on admission." Cases of MRSA first isolated on day 4 and thereafter, were defined as "new detection after admission." Statistical analysis was used to investigate the risk factors associated with MRSA isolation.

RESULTS

MRSA was isolated from 167 of 1,008 patients (carriage: 47; new detection: 120). Multivariate analysis revealed that the risk factors for MRSA carriage were activities of daily living (ADL) disability prior to admission (odds ratio [OR], 2.92; 95% confidence interval [CI], 1.37-6.22) and hospitalization within the previous 90 days (OR, 3.75; 95% CI, 1.90-7.41). ADL disability prior to admission (risk ratio [RR], 1.82; 95% CI, 1.17-2.84) and a high pneumonia severity index score upon admission (RR, 2.20; 95% CI, 1.37-3.65) were risk factors for new detection of MRSA.

CONCLUSIONS

Several risk factors were found to be associated with MRSA carriage and/or its new detection, based on the sputum samples from patients admitted with pneumonia. These factors may be indicators for selective surveillance and the early implementation of infection control measures.

Oral meal intake as a prognostic predictor of community-acquired pneumonia: A retrospective cohort study

INTRODUCTION

The association between oral intake volume and prognosis has not been studied in hospitalized patients with community-acquired pneumonia (CAP).

METHODS

We retrospectively examined 503 hospitalized CAP patients to evaluate whether early-phase meal intake (EMI) (within the first 24 h after hospitalization) and maximum meal intake (MMI) (on the day during hospitalization) are useful prognostic predictors.

RESULTS

Of the 503 patients, 40 (8.0%) died within 30 days. Area under the curve (AUC) for prognosis was comparable between EMI, A-DROP, and serum albumin [EMI: 0.80, 95% confidence interval (CI) 0.75-0.84; A-DROP: 0.77, 95% CI 0.71-0.83; Serum albumin: 0.72, 95% CI 0.64-0.79]. Mortality rate was <1% in patients with EMI ≥ 50%. Univariate analysis showed that patients with EMI < 50% showed poor prognosis [odds ratio 53.4, 95% CI 7.2-392.2]. Multivariate analysis showed that EMI was an independent prognostic predictor [odds ratio 23.6, 95% CI 3.11-179.7]. AUC of MMI for prognosis was 0.94 (95% CI 0.91-0.96); mortality rate was <1% for patients who ingested ≥50% of meals on any day during hospitalization. We defined ingesting ≥50% of meals on any day during hospitalization as oral intake stability. Multivariate analyses revealed an association between oral intake stability and prognosis. Odds ratio of oral intake stability for prognosis was higher than that of conventional evaluations (vital sign and CRP level stability). Fewer days were required to reach oral intake stability than to reach vital sign and CRP level stability.

CONCLUSIONS

Oral intake is a simple, non-invasive, cost-free, and powerful prognostic predictor for patients with CAP.

Comparison of ceftriaxone plus macrolide and ampicillin/sulbactam plus macrolide in treatment for patients with community-acquired pneumonia without risk factors for aspiration: an open-label, quasi-randomized, controlled trial

Background

Ceftriaxone (CTRX) and ampicillin/sulbactam (ABPC/SBT) are recommended by various guidelines as the first-line antibiotics for community-acquired pneumonia (CAP). However, which of these antibiotics is more effective for treating non-aspiration CAP remains unclear.

Methods

This study was a prospective, single-center, open-label, quasi-randomized controlled trial. Patients with adult CAP without risk for aspiration were allocated to either a CTRX or ABPC/SBT group based on the date of hospital admission. Macrolide was added to patients in each group. The primary outcome was the clinical response in the validated per-protocol (VPP) population at end of treatment (EOT). The secondary outcomes were clinical response during treatment and at end of study (EOS) in the VPP population, and mortality rate at day 30 in the modified intention-to-treat (MITT) population.

Results

Of 696 screened patients, 433 patients were excluded and 263 patients were allocated to receive either of the treatments. Males comprised 54% of patients and mean age and PSI were 62.1 ± 19.8 years and 69.3 ± 30.0, respectively, with 124 patients allocated to the CTRX group and 138 patients allocated to the ABPC/SBT group. The clinical effectiveness rate for the VPP population at EOT was 90% in the CTRX and 96% in the ABPC/SBT group (p = 0.072, 95% confidence interval [CI] of risk difference [RD]: − 12.6–0.8%). No significant difference in effectiveness at day 4 was observed between the CTRX and ABPC/SBT groups (p = 0.079, 95%CI of RD: − 12.1–0.4%), but at day 7, ABPC/SBT was significantly more effective than CTRX in the VPP population (p = 0.047, 95%CI of RD: − 13.3–-0.4%). No significant difference in late response at EOS was seen between CTRX and ABPC/SBT groups: cure (89 [86%] and 102 [94%]), relapse (5 [5%] and 1 [1%]) and failure (10 [10%] and 5 [5%]; p = 0.053). Deaths within 30 days in MITT population was higher in CTRX group (4 [3%]) than in ABPC/SBT group (0 [0%]) (p = 0.048, 95%CI of RD: 0.1–6.3%).

Conclusion

No significant difference in effectiveness was found between ABPC/SBT and CTRX at EOT. However, ABPC/SBT might be more effective in the early phase of treatment.

Trial registration

UMIN-CTR, UMIN000037464. Registered 25 July 2019 – Retrospectively registered, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000042262

Antibacterial treatment of aspiration pneumonia in older people: a systematic review

Background

Aspiration pneumonia is a common problem in older people with high mortality and increasing prevalence.

Objective

The aims of this paper were to systematically review the literature on the antibacterial treatment of aspiration pneumonia in elderly patients and identify the microbiology of aspiration pneumonia.

Materials and methods

EMBASE, MEDLINE, and Cochrane databases were systematically searched for studies that examined the clinical efficacy of antibiotic treatment in elderly patients with aspiration pneumonia. Information on study design, antibiotic treatment, study population, participants, microbiology, clinical outcomes, adverse events, and mortality was recorded.

Results

There were no definitive clinical trials, placebo-controlled trials, or meta-analyses. Of the eight studies selected for inclusion in the review, the majority utilized and/or compared broad-spectrum antibiotics. No specific antibacterial agent had evidence of superior efficacy. Broad-spectrum antibiotics resulted in the emergence of multiresistant organisms. Anaerobic bacteria were infrequently isolated, suggesting a less important role in the pathogenesis of aspiration pneumonia.

Conclusion

There is limited evidence with regard to the use of antibiotics in older patients with aspiration pneumonia. Research providing an evidence base for the treatment of aspiration pneumonia in older people is required.

Clostridium difficile infection following systemic antibiotic administration in randomised controlled trials: a systematic review and meta-analysis

Antibiotics have been the most important risk factor for Clostridium difficile infection (CDI). However, only data from non-randomised studies have been reviewed. We sought to evaluate the risk for development of CDI associated with the major antibiotic classes by analysing data from randomised controlled trials (RCTs). The PubMed, Cochrane and Scopus databases were searched and the references of selected RCTs were also hand-searched. Eligible studies should have compared only one antibiotic versus another administered systemically. Inclusion of studies comparing combinations of antibiotics was allowed only if the second antibiotic was the same or from the same class or if it was administered in a subset of the enrolled patients who were equally distributed in the two arms. Only a minority of the selected RCTs (79/1332; 5.9%) reported CDI episodes. Carbapenems were associated with more CDI episodes than fluoroquinolones [risk ratio (RR) = 2.44, 95% confidence interval (CI) 1.32-4.49] and cephalosporins (RR = 2.24, 95% CI 1.46-3.42), but not penicillins (RR = 2.53, 95% CI 0.87-7.41). Cephalosporins were associated with more CDIs than penicillins (RR = 2.36, 95% CI 1.32-4.23) and fluoroquinolones (RR = 2.84, 95% CI 1.60-5.06). There was no difference in CDI frequency between fluoroquinolones and penicillins (RR = 1.34, 95% CI 0.55-3.25). Finally, clindamycin was associated with more CDI episodes than cephalosporins and penicillins (RR = 3.92, 95% CI 1.15-13.43). In conclusion, data from RCTs showed that clindamycin and carbapenems were associated with more CDIs than other antibiotics.

Aspiration and Non-Aspiration Pneumonia in Hospitalized Children With Neurologic Impairment

BACKGROUND AND OBJECTIVE

Children with neurologic impairment (NI) are commonly hospitalized for different types of pneumonia, including aspiration pneumonia. We sought to compare hospital management and outcomes of children with NI diagnosed with aspiration versus nonaspiration pneumonia.

METHODS

A retrospective study of 27 455 hospitalized children aged 1 to 18 years with NI diagnosed with pneumonia from 2007 to 2012 at 40 children's hospitals in the Pediatric Health Information System database. The primary exposure was pneumonia type, classified as aspiration or nonaspiration. Outcomes were complications (eg, acute respiratory failure) and hospital utilization (eg, length of stay, 30-day readmission). Multivariable regression was used to assess the association between pneumonia type and outcomes, adjusting for NI type, comorbid conditions, and other characteristics.

RESULTS

In multivariable analysis, the 9.7% of children diagnosed with aspiration pneumonia experienced more complications than children with nonaspiration pneumonia (34.0% vs 15.2%, adjusted odds ratio [aOR] 1.2 (95% confidence interval [CI] 1.1-1.3). Children with aspiration pneumonia had significantly longer length of stay (median 5 vs 3 days; ratio of means 1.2; 95% CI 1.2-1.3); more ICU transfers (4.3% vs 1.5%; aOR 1.4; 95% CI 1.1-1.9); greater hospitalization costs (median $11 594 vs $5162; ratio of means 1.2; 95% CI 1.2-1.3); and more 30-day readmissions (17.4% vs 6.8%; aOR 1.3; 95% CI 1.2-1.5).

CONCLUSIONS

Hospitalized children with NI diagnosed with aspiration pneumonia have more complications and use more hospital resources than when diagnosed with nonaspiration pneumonia. Additional investigation is needed to understand the reasons for these differences.

Clinical effect of biapenem on nursing and healthcare-associated pneumonia (NHCAP)

The clinical effect of Biapenem (BIPM) on Nursing and Healthcare-associated pneumonia (NHCAP) was evaluated. One hundred and three NHCAP patients (Group B: 52 patients, Group C: 51 patients) to whom BIPM was administered were included in this study. Clinical effect, bacteriological effect, and adverse events were examined. Results revealed efficacy in 45 of 52 patients (efficacy rate: 86.5%) of NHCAP Group B, and 43 of 51 patients (efficacy rate: 84.3%) of NHCAP Group C, 88 of 103 patients (efficacy rate: 85.4%) as a whole. As for bacteriological effect, 10 (76.9%) of 13 Pseudomonas aeruginosa strains, 9 (90.0%) of 10 Klebsiella pneumoniae strains, 7 (87.5%) of 8 methicillin-sensitive Staphlococcus aureus strains, and 7 (100%) of 7 Streptococcus pneumonia strains were eradicated. As a whole, 38 (80.9%) of 47 strains were eradicated. Adverse events included drug fever and drug eruption in one patient each, and abnormal laboratory findings, including mild hepatic dysfunction in 18 patients and mild renal dysfunction in 5 patients. Based on the above, it was concluded that BIPM shows excellent clinical effect on NHCAP with fewer adverse events.

Participation of elderly adults in randomized controlled trials addressing antibiotic treatment of pneumonia

OBJECTIVES

To examine how relevant current evidence on antibiotic treatment of pneumonia is for elderly adults.

DESIGN

Systematic review.

SETTING

Randomized controlled trials (RCTs; N = 43) comparing different antibiotics and prospective observational studies (N = 182) published since 2005.

PARTICIPANTS

Adults with community-acquired (CAP), healthcare-associated (HCAP), hospital-acquired (HAP), or ventilator-associated (VAP) pneumonia.

MEASUREMENTS

Exclusion criteria that could preferentially limit participation of elderly adults were examined, subgroup or other adjusted analyses were searched for according to age, and treatment effects in participants younger than 65 in RCTs were compared with those in participants aged 65 and older. Mean participant ages in RCTs and observational studies were compared. Risk ratios (RRs) with 95% confidence intervals (CIs) for differences between older and younger adults were pooled using a fixed effect metaanalysis.

RESULTS

No RCT reported exclusion based on an upper age limit; 100% of community CAP trials, 90% of hospitalized CAP trials, and 76% of HAP and VAP trials excluded individuals based on comorbidities. None of the RCTs reported a subgroup analysis for mortality according to age. The RR for the pooled difference in treatment failure rates between participants younger than 65 and those aged 65 and older was 1.25 (95% CI = 0.94-1.65, 12 RCTs) and between participants younger than 75 and aged 75 and older was 1.43 (95% CI = 0.98-2.09, 7 RCTs). RCT participants were significantly younger (54.0 ± 9.6) than those in observational studies of CAP (66.2 ± 8.1, P < .001). Age differences were not significant for HCAP, HAP, and VAP.

CONCLUSION

Elderly adults are often excluded from RCTs of bacterial pneumonia. No data were found on the comparative efficacy of antibiotic treatment in elderly adults and the general population.

Update on the pathogenesis and management of pneumonia in the elderly-roles of aspiration pneumonia

Pneumonia in the elderly results in the highest mortality among cases of community-acquired pneumonia (CAP). The pathophysiology of pneumonia in the elderly is primarily due to aspiration pneumonia (ASP). ASP comprises two pathological conditions: airspace infiltration with bacterial pathogens and dysphagia-associated miss-swallowing. The first-line therapy for the treatment of bacterial pneumonia in the elderly is a narrow spectrum of antibiotics, including sulbactam/ampicillin, which are effective against major lower respiratory infection pathogens and anaerobes. The bacterial pathogens of ASP cases of pneumonia in the elderly are similar to those associated with adult CAP. In addition to an appropriate course of antibiotics, pharmacologic and non-pharmacologic approaches for dysphagia and upper airway management are necessary for the treatment and prevention of pneumonia. Swallowing rehabilitation, oral health care, pneumococcal vaccination, gastroesophageal reflux management, and a head-up position during the night are necessary for the treatment and prevention of repeated episodes of pneumonia in elderly patients. In addition, tuberculosis should always be considered for the differential diagnosis of pneumonia in this patient population.

β-Lactam/β-lactamase inhibitors versus carbapenems for the treatment of sepsis: systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Data on the relative efficacy of β-lactam/β-lactamase inhibitors (BL/BLIs) versus carbapenems are scant.

METHODS

This is a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing any BL/BLI versus any carbapenem for the treatment of sepsis. The primary outcome was all-cause mortality. A broad search was conducted with no restrictions on language, publication status or date. Two reviewers independently applied the inclusion criteria and extracted the data. Assessment of risk of bias was performed using the domain-based approach. Subgroup analyses were used to investigate heterogeneity and focus on patient groups more likely to harbour ESBL-positive bacteria. Risk ratios (RRs) with 95% CIs were calculated and pooled.

RESULTS

Thirty-one RCTs were included. There was no difference between BL/BLIs and carbapenems in terms of mortality (RR 0.98, 95% CI 0.79-1.20), without heterogeneity. No differences were observed with regard to clinical or microbiological failure and bacterial superinfections. The results were not affected by risk of bias. No differences were detected in the subgroups of patients with nosocomial infections, Gram-negative infections and neutropenic fever. Adverse events requiring discontinuation were more common with BL/BLIs, on account of an increased incidence of diarrhoea. However, Clostridium difficile-associated diarrhoea (RR 0.29, 95% CI 0.10-0.87) was more frequent with carbapenems and seizures were more frequent with imipenem (RR 0.21, 95% CI 0.05-0.93).

CONCLUSIONS

No differences in efficacy between BL/BLIs and carbapenems exist in RCTs including patient populations with a certain, albeit unknown, rate of ESBL-positive bacteria causing infections.

Assessment of bias in outcomes reported in trials on pneumonia: a systematic review

Subjective outcomes may exaggerate intervention effects compared to objectively measured outcomes. We compared effect estimates for clinical failure and all-cause mortality clinical trials of antibiotic treatment for pneumonia. A systematic review of randomized controlled trials assessing adults with pneumonia, comparing different antibiotics, published between 2005 and 2012 was undertaken. We compared the intervention to the control arm. The all-cause mortality in the intention-to-treat population and clinical failure as defined by the study investigators for the primary analyzed population were the primary outcomes examined. Risk ratios (RRs) with 95 % confidence intervals (CIs) were pooled, using a fixed effect model. Meta-regression was used to examine the impact of clinical failure on the mortality effect size. Thirty-six trials were included, of which 30 were industry-sponsored and 30 were non-inferiority trials. There was no difference between the effect on mortality for intervention versus control (RR 1.02, 95 % CI 0.91-1.16) and clinical failure (RR 1.01, 95 % CI 0.93-1.10), without significant heterogeneity in both analyses. In double-blind trials with adequate sequence generation and concealment, there was a significant advantage to the intervention for clinical failure (RR 0.86, 95 % CI 0.76-0.98), but not for mortality (RR 0.96, 95 % CI 0.76-1.21). RRs for clinical failure did not explain the variability in the RRs for mortality significantly, with a meta-regression coefficient of 0.32 (95 % CI -0.21-0.85). In non-inferiority trials of antibiotic treatment for pneumonia, we did not find evidence for bias induced by the use of a subjective outcome overall. The small number of trials without sponsorship precludes an adequate assessment of sponsorship effects.