Methods for deriving risk difference (absolute risk reduction) from a meta-analysis

Interval breast cancer rates for tomosynthesis vs mammography population screening: a systematic review and meta-analysis of prospective studies

OBJECTIVES

We aimed to synthesise evidence from prospective studies of digital breast tomosynthesis (DBT) screening to assess its effectiveness compared to digital mammography (DM). Specifically, we examined whether DBT reduces interval cancer rates (ICRs) in population breast cancer screening.

MATERIALS AND METHODS

We performed a systematic review and meta-analysis of DBT screening studies (identified from January 2013 to March 2024). We included both RCTs and non-randomised prospective studies that used an independent comparison for our primary outcome ICRs. The risk of bias was assessed with QUADAS-2. We compared the ICR, cancer detection rate (CDR), and recall rate of DBT and DM screening using random effects meta-analysis models. Subgroup analyses estimated outcomes by study design. Sensitivity analyses estimated absolute effects from relative effects.

RESULTS

Ten prospective studies (three RCTs, seven non-randomised) were eligible; all had a low risk of bias. There were 205,245 DBT-screened and 306,476 DM-screened participants with follow-up for interval cancer data. The pooled absolute ICR did not significantly differ between DBT and DM: -2.92 per 10,000 screens (95% CI: -6.39 to 0.54); however subsequent subgroup analysis indicated certain study designs may have biased this ICR estimate. Pooled ICR from studies that only sampled groups from the same time and region indicated DBT led to 5.50 less IC per 10,000 screens (95% CI: -9.47 to -1.54). Estimates from subgroup analysis that compared randomised and non-randomised trials did not significantly differ.

CONCLUSION

This meta-analysis provides suggestive evidence that DBT decreases ICR relative to DM screening; further evidence is needed to reduce uncertainty regarding ICR differences between DBT and DM.

KEY POINTS

Question Does DBT have long-term benefits over standard DM? Finding We find suggestive evidence in our primary analysis and stronger evidence in a follow-up analysis that DBT reduces interval cancers. Clinical relevance This meta-analysis provides the first indication that DBT may detect additional cancers that are clinically meaningful, based on suggestive evidence of a reduction in ICR. This finding does not preclude the simultaneous possibility of overdiagnosis.

Bleeding Risks With Non-Vitamin K Oral Anticoagulants Versus Single Antiplatelet Therapy : A Systematic Review and Meta-analysis of Randomized Trials

BACKGROUND

In several settings, therapeutic-dose non-vitamin K oral anticoagulants (NOACs) are superior to aspirin for the prevention of arterial and venous thromboembolism.

PURPOSE

To estimate differences in bleeding risks between NOACs and single antiplatelet therapy.

DATA SOURCES

MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from inception to June 2024 without language restrictions.

STUDY SELECTION

Randomized controlled trials (RCTs) comparing therapeutic-dose NOACs versus single antiplatelet therapy, with a minimum treatment duration of 3 months.

DATA EXTRACTION

Data extraction was done independently and in duplicate.

DATA SYNTHESIS

Nine RCTs with 26 224 participants were included. All studies used aspirin as antiplatelet therapy. Compared with aspirin, apixaban had similar rates of major bleeding (risk difference [RD], 0.0 percentage point [95% CI, -1.3 to 2.6 percentage points]; 5 trials) and intracranial hemorrhage (RD, -0.2 percentage point [CI, -0.6 to 1.4 percentage points]; 5 trials). Compared with aspirin, dabigatran had similar rates of major bleeding (RD, 0.5 percentage point [CI, -2.1 to 19.6 percentage points]; 2 trials) and intracranial hemorrhage (RD, 0.0 percentage point [CI, -1.1 to 24.5 percentage points]; 2 trials). Compared with aspirin, rivaroxaban had higher rates of major bleeding (RD, 0.9 percentage point [CI, -0.1 to 3.7 percentage points]; 2 trials) and intracranial hemorrhage (RD, 0.3 percentage point [CI, -0.1 to 79.7 percentage points]; 2 trials). The evidence certainty ranged from low to moderate.

LIMITATION

Confidence intervals were wide and included the possibility of a null effect.

CONCLUSION

In this systematic review of RCTs, rates of major bleeding for therapeutic-dose apixaban and dabigatran were similar to those for low-dose aspirin, whereas rates were higher for rivaroxaban.

PRIMARY FUNDING SOURCE

None. (PROSPERO: CRD42024553683).

Impact of sodium intake on blood pressure, mortality and major cardiovascular events: an umbrella review of systematic reviews and meta-analyses

A plethora of systematic reviews with meta-analyses (SRMAs) evaluating sodium intake on cardiovascular health have been published. However, the quality of the SRMAs, that report absolute estimates of effect for major cardiovascular events and the corresponding certainty of the evidence has not been explicitly summarized. We conducted an umbrella review to assess the strength and validity of associations between lower sodium intake and cardiovascular outcomes. We used a modified, more stringent, version of the AMSTAR 2 instrument and the GRADE approach to assess SRMA methodological quality and evidence certainty, respectively. Across three cardiovascular risk strata, we computed the absolute risk reduction (ARR) for binary outcomes. We included 56 SRMAs. In various cardiovascular risk populations, moderate to high certainty evidence suggested that lower sodium intake reduced systolic blood pressure (BP) by -8.69 to -2.00 mmHg, and had concordant but smaller effects on diastolic BP. Salt substitutes conferred a small but important reduction in all-cause and cardiovascular mortality [ARR 12 fewer per 1000; 9 fewer per 1000; respectively], and had little to no effect on the risk of stroke [ARR 1 fewer per 1000]. Moderate to high certainty evidence suggested that lower sodium intake is probably beneficial for the prevention of major cardiovascular events, especially in low cardiovascular risk populations.

Postoperative outcomes among Northern versus Southern Ontario patients undergoing common intermediate- to high-risk elective surgeries: a population-based cohort study

PURPOSE

Northern Ontario residents experience multiple health disparities compared with those in Southern Ontario. It is unknown whether this leads to differences in surgical outcomes. We sought to compare postoperative outcomes of patients from Northern and Southern Ontario.

METHODS

We conducted a retrospective population-based cohort study using linked administrative health care data to identify all adult patients undergoing selected elective intermediate- to high-risk noncardiac surgeries in Ontario, Canada between 2009 and 2022. The primary outcome was 30-day mortality following surgery. The secondary outcomes were number of days alive at home, hospital length of stay, total health care system costs, discharge disposition, and readmissions. We used regression models to estimate the adjusted association between the exposure and outcomes.

RESULTS

This study identified 562,115 patients, including 41,191 (7.3%) from Northern Ontario. We did not find strong evidence that mortality rates were higher for Northern vs Southern Ontario residents (adjusted odds ratio, 1.04; 95% confidence interval [CI], 0.85 to 1.27). Health system costs were lower for Northern Ontario residents at 30 days [adjusted ratio of mean (RoM), 0.92; 95% CI, 0.89 to 0.96] and at 365 days (adjusted RoM, 0.93; 95% CI, 0.90 to 0.96). Hospital length of stay was longer for Northern Ontario residents (adjusted RoM, 1.06; 95% CI, 1.01 to 1.11). The number of days alive at home and rate of readmission were not statistically different between the two groups.

CONCLUSION

Northern Ontario residency was not associated with increased odds of mortality after intermediate- to high-risk elective noncardiac surgery. Overall, we found no clinically meaningful differences in postoperative outcomes between patients from Northern and Southern Ontario.

Exploring the characteristics, methods and reporting of systematic reviews with meta-analyses of time-to-event outcomes: a meta-epidemiological study

BACKGROUND

Time-to-event analysis is associated with methodological complexities. Previous research identified flaws in the reporting of time-to-event analyses in randomized trial publications. These hardships impose challenges for meta-analyses of time-to-event outcomes based on aggregate data. We examined the characteristics, reporting and methods of systematic reviews including such analyses.

METHODS

Through a systematic search (02/2017-08/2020), we identified 50 Cochrane Reviews with ≥ 1 meta-analysis based on the hazard ratio (HR) and a corresponding random sample (n = 50) from core clinical journals (Medline; 08/02/2021). Data was extracted in duplicate and included outcome definitions, general and time-to-event specific methods and handling of time-to-event relevant trial characteristics.

RESULTS

The included reviews analyzed 217 time-to-event outcomes (Median: 2; IQR 1-2), most frequently overall survival (41%). Outcome definitions were provided for less than half of time-to-event outcomes (48%). Few reviews specified general methods, e.g., included analysis types (intention-to-treat, per protocol) (35%) and adjustment of effect estimates (12%). Sources that review authors used for retrieval of time-to-event summary data from publications varied substantially. Most frequently reported were direct inclusion of HRs (64%) and reference to established guidance without further specification (46%). Study characteristics important to time-to-event analysis, such as variable follow-up, informative censoring or proportional hazards, were rarely reported. If presented, complementary absolute effect estimates calculated based on the pooled HR were incorrectly calculated (14%) or correct but falsely labeled (11%) in several reviews.

CONCLUSIONS

Our findings indicate that limitations in reporting of trial time-to-event analyses translate to the review level as well. Inconsistent reporting of meta-analyses of time-to-event outcomes necessitates additional reporting standards.

Risk of Common Neurological Disorders in Adult Patients with Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND

Several studies investigated the risks of neurological conditions in patients with inflammatory bowel disease (IBD), with some variability in findings. We aimed to perform a systematic review and meta-analysis of available evidence to elucidate the association between IBD and the risks of common neurological disorders.

METHODS

We conducted a literature search through Embase, PubMed, Scopus, and ProQuest databases from inception to June 30, 2023, to identify cohort studies assessing the risk of developing stroke, all-cause dementia, Parkinson's disease (PD), multiple sclerosis (MS), seizure/epilepsy, and peripheral neuropathy in adult IBD patients compared with non-IBD population. We combined hazard ratios (HRs) with 95% confidence intervals (CIs) to compute pooled estimates using a random-effects model.

RESULTS

In total, 22 cohort studies were included, of which 9 studies reported 7074 stroke events in 202 460 IBD patients, 5 studies reported 3783 all-cause dementia diagnoses in 109 602 IBD patients, 7 studies reported 932 PD diagnoses in 354 792 IBD patients, and 1 study reported 6 MS events in 35 581 IBD patients. We observed increased risks of incident stroke (pooled HR = 1.19; 95% CI, 1.06-1.31), all-cause dementia (pooled HR = 1.22; 95% CI, 1.05-1.38), PD (pooled HR = 1.39; 95% CI, 1.20-1.58), and MS (HR = 2.89; 95% CI, 1.02-8.42). No eligible studies were found on peripheral neuropathy and seizure/epilepsy.

CONCLUSIONS

Inflammatory bowel disease may be modestly associated with increased risks of stroke, all-cause dementia, and PD. Further longitudinal studies are warranted to investigate potential links with MS, seizure/epilepsy, and peripheral neuropathy, as well as their clinical significance.

Meta-analysis: Risk of lymphoma in patients with inflammatory bowel disease in population-based cohort studies

BACKGROUND

There are inconsistencies in the results of the studies investigating the association between inflammatory bowel disease (IBD) and lymphoma.

AIMS

The aim of this study is to systematically appraise the risk of lymphoma development in patients with IBD.

METHODS

We searched Embase, PubMed and Scopus from inception to 30 April 2024 to identify population-based cohort studies that evaluated the risk of lymphoma in patients with IBD in comparison with those without IBD. We carried out random-effects meta-analyses and estimated pooled relative risks (RRs) with 95% confidence intervals (CIs).

RESULTS

We identified 23 eligible studies reporting 2078 lymphoma events in 656,731 patients with IBD. Patients with IBD had 30% higher odds of lymphoma (RR = 1.30 [95% CI: 1.21-1.40]). The risk of developing both Hodgkin's lymphoma (nine studies, RR = 1.29 [95% CI: 1.06-1.53]) and non-Hodgkin's lymphoma (16 studies, RR = 1.31 [95% CI: 1.20-1.42]) was increased in patients with IBD (p for interaction = 0.881). The increased risk of lymphoma was observed in both Crohn's disease (17 studies, RR = 1.54 [95% CI: 1.27-1.80]) and ulcerative colitis (20 studies, RR = 1.22 [95% CI: 1.09-1.35]) (p for interaction = 0.026). Meta-regression demonstrated that mean age of patients, study year, mean study follow-up duration, and percentages of immunomodulators and biologics use did not influence study outcome.

CONCLUSIONS

The risk of lymphoma is only modestly increased in patients with IBD, with Crohn's disease having a slightly higher risk than ulcerative colitis. In IBD, there appears to be no difference between the risks of Hodgkin's and non-Hodgkin's lymphoma.

Variability of relative treatment effect among populations with low, moderate and high control group event rates: a meta-epidemiological study

BACKGROUND

The current practice in guideline development is to use the control group event rate (CR) as a surrogate of baseline risk and to assume portability of the relative treatment effect across populations with low, moderate and high baseline risk. We sought to emulate this practice in a very large sample of meta-analyses.

METHODS

We retrieved data from all meta-analyses published in the Cochrane Database of Systematic Reviews (2003-2020) that evaluated a binary outcome, reported 2 × 2 data for each individual study and included at least 4 studies. We excluded studies with no events. We conducted meta-analyses with odds ratios and relative risks and performed subgroup analyses based on tertiles of CR. In sensitivity analyses, we evaluated the use of total event rate (TR) instead of CR and using quartiles instead of tertiles.

RESULTS

The analysis included 2,531 systematic reviews (27,692 meta-analyses, 226,975 studies, 25,669,783 patients).The percentages of meta-analyses with statistically significant interaction (P < 0.05) based on CR tertile or quartile ranged 12-18% across various sensitivity analyses. This percentage increased as the number of studies or range of CR per meta-analysis increased, reflecting increased power of the subgroup test. The percentages of meta-analyses with statistically significant interaction (P < 0.05) with TR quantiles were lower than those with CR but remained higher than expected by chance.

CONCLUSION

This analysis suggests that when CR or TR are used as surrogates for baseline risk, relative treatment effects may not be portable across populations with varying baseline risks in many meta-analyses. Categroization of the continuous CR variable and not addressing measurement error limit inferences from such analyses and imply that CR is an undesirable source for baseline risk. Guideline developers and decision-makers should be provided with relative and absolute treatment effects that are conditioned on the baseline risk or derived from studies with similar baseline risk to their target populations.

Tipping point analysis for the between-arm correlation in an arm-based evidence synthesis

Systematic reviews and meta-analyses are essential tools in contemporary evidence-based medicine, synthesizing evidence from various sources to better inform clinical decision-making. However, the conclusions from different meta-analyses on the same topic can be discrepant, which has raised concerns about their reliability. One reason is that the result of a meta-analysis is sensitive to factors such as study inclusion/exclusion criteria and model assumptions. The arm-based meta-analysis model is growing in importance due to its advantage of including single-arm studies and historical controls with estimation efficiency and its flexibility in drawing conclusions with both marginal and conditional effect measures. Despite its benefits, the inference may heavily depend on the heterogeneity parameters that reflect design and model assumptions. This article aims to evaluate the robustness of meta-analyses using the arm-based model within a Bayesian framework. Specifically, we develop a tipping point analysis of the between-arm correlation parameter to assess the robustness of meta-analysis results. Additionally, we introduce some visualization tools to intuitively display its impact on meta-analysis results. We demonstrate the application of these tools in three real-world meta-analyses, one of which includes single-arm studies.

Meta-analysis: Risk of pancreatic cancer in patients with inflammatory bowel disease

BACKGROUND

Studies exploring the association between inflammatory bowel disease (IBD) and pancreatic cancer have reported inconsistent results.

AIMS

To provide a comprehensive overview of the risk of pancreatic cancer development in patients with IBD.

METHODS

We searched Embase, PubMed, Scopus and ProQuest from inception to 31 October 2023. We included population-based cohort studies examining the risk of incident pancreatic cancer in adult patients with IBD compared to the non-IBD population. We also retrieved Mendelian randomisation (MR) studies investigating the relationship of IBD with pancreatic cancer risk. We conducted random-effects meta-analyses and provided pooled relative risks (RRs) with 95% confidence intervals (CIs).

RESULTS

We included 13 studies. Among 11 cohort studies, the risk of developing pancreatic cancer increased by 79% in patients with IBD (RR = 1.79 [95% CI: 1.16-2.75]; I2 = 95.7%). Patients either with Crohn's disease (RR = 1.42 [95% CI: 1.24-1.63]) or ulcerative colitis (RR = 1.50 [95% CI: 1.17-1.92]) had increased risk (p for interaction = 0.72). The annual incidence of pancreatic cancer potentially attributable to IBD increased by 55 cases (95% CI: 17-103) per million. Two MR studies demonstrated that genetic liability to IBD was associated with an increased risk of pancreatic cancer.

CONCLUSIONS

Our results suggest a moderate increase in the risk of pancreatic cancer in patients with IBD, which may be further heightened by genetic predisposition to IBD. The increased risk of pancreatic cancer is probably similar in Crohn's disease and ulcerative colitis.

Effectiveness of adjunctive rifampicin for treatment of Staphylococcus aureus bacteraemia: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

To assess whether the addition of rifampicin to conventional treatment of Staphylococcus aureus bacteraemia (SAB) reduces bacteriological or clinical failure or death.

DATA SOURCES

PubMed, Embase and Cochrane CENTRAL databases were searched from inception to 31 December 2022. Reference lists and PubMed citations of eligible studies were checked.

REVIEW METHODS

Two study authors independently identified randomized controlled trials (RCTs) involving adult participants with SAB, in which an intervention group received adjunctive rifampicin and the control group received usual care with or without a placebo. Dichotomous data (bacteriological and clinical failure and deaths) were analysed and pooled across studies using risk ratio (RR) with 95% confidence intervals (CI) using a Mantel-Haenszel random-effect model. The key variable of interest being whether rifampicin was used.

RESULTS

Six RCTs including 894 participants-of which 758 (85%) were from one trial-met the inclusion criteria. The addition of rifampicin to conventional treatment of SAB significantly reduced bacteriological failure by 59% (RR 0.41, 95% CI 0.21-0.81, I2 = 0%, number need to treat 27). However, it did not reduce clinical failure (RR 0.70, 95% CI 0.47-1.03, I2 = 0%) or deaths (RR 0.96, 95% CI 0.70-1.32, I2 = 0%). Further, it did not reduce the duration of bacteraemia, or the length of hospital stay. Adjunctive rifampicin reduced SAB recurrences (1% versus 4%, P = 0.01). Emergence of rifampicin resistance during treatment was uncommon (<1%).

CONCLUSION

Although adjunctive rifampicin reduced the risk of bacteriological failure and recurrences, we found no mortality benefit to support its use in SAB.