The necessity and methods of systematic review or Meta-analysis of observational studies were introduced. The difference between the systematic review or Meta-analysis of observational studies and randomized controlled trials was also described.
Observational studies based on real-world data are providing increasing amount of evidence for evaluating therapeutic outcomes, which is important for timely decision-making. Although time and costs for data collection could be saved using real-world data, it is significantly more complex to design real world researches with lower risk of bias. In order to enhance the validity of causal inference and to reduce potential risk of bias in real world studies, the Working Group of China Real world data and studies Alliance (China REAL) has formulated recommendations for designing observational studies to evaluate therapeutic outcomes based on real-world data. This guidance introduces design types commonly used in real world research; recommends key elements to consider in observational studies, including sample selection, specifying and allocating exposures, defining study entry and endpoints, and pre-designing statistical analysis protocols; and summarizes potential biases and corresponding control measures in real-world studies. These recommendations introduces key elements in designing observational studies using real-world data, for the purpose of improving the validity of causal inference. However, the application scope of these recommendations may be limited and warrant constant improvement.
Assessment of Real World Observational Studies (ArRoWS) is a tool developed by the Leicester Real World Evidence (LRWE) Unit of the Diabetes Research Centre of the University of Leicester in the United Kingdom to assess the quality of real world evidence research, and has been reported to have good practicability. ArRoWS can be used to quickly and specifically assess the quality of real world evidence research that uses electronic health record information. The tool contains 16 items, nine of which are common items, and seven of which are related to specific research designs. The current study introduces the development background, development process, assessment items, assessment criteria, and application methods of ArRoWS and other related aspects, to provide references for real world researchers in China.
Objective To investigate the methodological characteristics of observational studies on the correlation between drug exposure during pregnancy and birth defects. Methods The PubMed database was searched from January 1, 2020 to December 31, 2020 to identify observational studies investigating the correlation between drug use during pregnancy and birth defects. Literature screening and data extraction were conducted by two researchers and statistical analysis was performed using R 3.6.1 software. Results A total of 40 relevant articles were identified, of which 8 (20.0%) were published in the four major medical journals and their sub-journals, 21 (42.5%) were conducted in Europe and the United States, and 4 were conducted (10.0%) in China. Cohort studies (30, 75.0%) and case-control studies (10, 25%) were the most commonly used study designs. Sixteen studies (40.0%) did not specify how the databases were linked. Sixteen studies (40.0%) did not report a clear definition of exposure, while 17 studies (42.5%) defined exposure as prescribing a drug that could not be guaranteed to have been taken by the pregnant women, possibly resulting in misclassification bias. Six studies (15.0%) did not report the diagnostic criteria for birth defects and 18 studies (45.0%) did not report the types of birth defects. In addition, 33 studies (82.5%) did not control for confounding factors in the study design, while only 19 studies (47.5%) considered live birth bias. Conclusion Improvements are imperative in reporting and conducting observational studies on the correlation between drug use during pregnancy and birth defects. This includes the methods for linking data sources, definition of exposure and outcomes, and control of confounding factors. Methodological criteria are needed to improve the quality of these studies to provide higher quality evidence for policymakers and researchers.
Objective To systematically review the association between periodontal disease during pregnancy and the risk of gestational diabetes mellitus (GDM). Methods PubMed, Web of Science, CBM and CNKI databases were electronically searched to collect studies on periodontal disease and GDM from inception to October 23, 2021. Two researchers independently screened literature, extracted data and assessed the risk of bias of the included studies. Meta-analysis was then performed using RevMan 5.4 software. Results A total of 11 studies were included, involving 2 910 pregnant women. The results of meta-analysis showed that pregnant women with periodontal disease during pregnancy reported more GDM than normal pregnant women (OR=1.81, 95%CI 1.31 to 2.50, P=0.000 3). Conclusion The current evidence suggests that there is a positive association between periodontal disease during pregnancy and the risk of GDM. Due to the limited quantity and quality of the included studies, more high-quality studies are needed to verify the above conclusion.
ObjectiveTo systematically review the effectiveness of breastfeeding duration and intensity in reducing the risk of overweight or obesity among offspring exposed to intrauterine hyperglycemia. MethodsThe PubMed, EMbase, Web of Science, CBM, WanFang Data, CNKI and VIP databases were electronically searched to collect observational studies on the associations of breastfeeding with the risk of overweight or obesity among offspring exposed to intrauterine hyperglycemia from inception to September 25th, 2021. Two reviewers independently screened the literature, extracted data and assessed the risk of bias of the included studies. Stata 16.0 software was used for the meta-analysis. ResultsA total of 12 657 participants from 13 observational studies were included. The results of meta-analysis showed that breastfeeding could reduce the risk of overweight or obesity among offspring exposed to intrauterine hyperglycemia (OR=0.67, 95%CI 0.53 to 0.84, P=0.001). Subgroup analysis revealed a protective effect of breastfeeding for both 1-6 months (OR=0.53, 95%CI 0.37 to 0.75, P<0.001) and ≥6 months (OR=0.56, 95%CI 0.46 to 0.69, P<0.001); however, breastfeeding shorter than one month was suggested to increase the risk of overweight or obesity (OR=2.15, 95%CI 1.41 to 3.27, P<0.001). ConclusionAvailable evidence suggests that breastfeeding for more than one month is effective in reducing the risk of overweight or obesity in offspring exposed to intrauterine hyperglycemia, and women with hyperglycemia should be encouraged to breastfeed their offspring for at least 1 month to achieve the effect. Due to the limited quantity and quality of the included studies, more high-quality studies are needed to verify the above conclusion.
ObjectiveTo assess whether pre-operative use of infliximab (IFX) will increase the risk of post-operative infectious complications in patients with inflammatory bowel disease (IBD). MethodsPubmed, Web of Science, CBM, CNKI and Wanfang database were searched for all the trials that investigated the effects of infliximab on postoperative infectious complication rates in patients with IBD between January 1990 and April 2013. Two reviewers independently screened the literature according to the inclusion and exclusion criteria, extracted data and assessed the quality of the included studies. Then, meta-analysis was performed using RevMan 5.1 software. ResultsTotally, 14 cohort studies were finally included in the review. There was no significant difference on infectious complications [RR=0.99, 95%CI (0.47, 2.07), P=0.97] between IFX groups and control groups with ulcerative colitis. The same results were found in patients with Crohn's disease on infectious complications [RR=1.32, 95%CI (0.87, 1.98), P=0.19]. ConclusionPre-operative infliximab use is safe and does not increase the risk of post-operative infectious complications in patients with IBD.
ObjectiveTo evaluate the association between H2RA and the risk of hip fracture by performing a meta-analysis. MethodsWe searched CNKI, PubMed and EMbase from inception to September 19th 2016, to collect case-control studies or cohort studies reporting the risk of hip fracture with H2RA. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then meta-analysis was performed using Stata 13 software. ResultsEleven studies involving 206 276 hip fracture cases were included. The result of meta-analysis showed that patients receiving H2RA therapy had approximately 1.12 times the risk of developing hip fracture compared with nonusers (OR=1.12 95%CI 1.02 to 1.24, P=0.022). Subgroup analyses by interval time indicated that the risk appeared greater with the continuous users (OR=1.11, 95%CI 1.01 to 1.24, P=0.039) whereas the discontinuous users was not significantly associated with hip fracture risk. ConclusionH2RA therapy may be associated with an increased risk of hip fracture. For patients with intermittent medication, the side effect may disappear by discontinuation of PPI use for at least 30 days, but the study did not find time-effect relationship or dose-effect relationship. Considering the limitations of this study, more rigorous clinical trials evaluating the potential side-effect of H2RA are needed.
Compared with traditional clinical trials, the real-world studies set higher requirements on the authenticity (reality), applicability, and timeliness of the evidence obtained. In this paper, we brought up a hypothesis that creating synergies between observational and experimental studies may meet these requirements. And then it was discussed in three aspects including providing evidence, research design and execution. In addition, data analysis facilitated generating efficient and robust evidence which was in support of decision making. Finally, some enlightenment may be offered for Traditional Chinese Medicine evaluation methods based on the synergies of both study types.
Nonrandomized studies are an important method for evaluating the effects of exposures (including environmental, occupational, and behavioral exposures) on human health. Risk of bias in nonrandomized studies of exposures (ROBINS-E) is used to evaluate the risk of bias in natural or occupational exposure observational studies. This paper introduces the main contents of ROBINS-E 2022, including backgrounds, seven domains, signal questions and the operation process.