High quality (certainty) evidence changes less often than low-quality evidence, but the magnitude of effect size does not systematically differ between studies with low versus high-quality evidence.

RATIONALE, AIMS, AND OBJECTIVES: It is generally believed that evidence from low quality of evidence generate inaccurate estimates about treatment effects more often than evidence from high (certainty) quality evidence (CoE). As a result, we would expect that (a) estimates of effects of health interventions initially based on high CoE change less frequently than the effects estimated by lower CoE (b) the estimates of magnitude of effect size differ between high and low CoE. Empirical assessment of these foundational principles of evidence-based medicine has been lacking. METHODS: We reviewed the Cochrane Database of Systematic Reviews from January 2016 through May 2021 for pairs of original and updated reviews for change in CoE assessments based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method. We assessed the difference in effect sizes between the original versus updated reviews as a function of change in CoE, which we report as a ratio of odds ratio (ROR). We compared ROR generated in the studies in which CoE changed from very low/low (VL/L) to moderate/high (M/H) versus M/H to VL/L. Heterogeneity and inconsistency were assessed using the tau and I2 statistic. We also assessed the change in precision of effect estimates (by calculating the ratio of standard errors) (seR), and the absolute deviation in estimates of treatment effects (aROR). RESULTS: Four hundred and nineteen pairs of reviews were included of which 414 (207 × 2) informed the CoE appraisal and 384 (192 × 2) the assessment of effect size. We found that CoE originally appraised as VL/L had 2.1 [95% confidence interval (CI): 1.19-4.12; p = 0.0091] times higher odds to be changed in the future studies than M/H CoE. However, the effect size was not different (p = 1) when CoE changed from VL/L → M/H [ROR = 1.02 (95% CI: 0.74-1.39)] compared with M/H → VL/L (ROR = 1.02 [95% CI: 0.44-2.37]). Similar overlap in aROR between the VL/L → M/H versus M/H → VL/L subgroups was observed [median (IQR): 1.12 (1.07-1.57) vs. 1.21 (1.12-2.43)]. We observed large inconsistency across ROR estimates (I2 = 99%). There was larger imprecision in treatment effects when CoE changed from VL/L → M/H (seR = 1.46) than when it changed from M/H → VL/L (seR = 0.72). CONCLUSIONS: We found that low-quality evidence changes more often than high CoE. However, the effect size did not systematically differ between the studies with low versus high CoE. The finding that the effect size did not differ between low and high CoE indicate urgent need to refine current EBM critical appraisal methods.

Strategies to deal with the COVID-19 pandemic

The World Health Organization declared a COVID-19 pandemic on March 11, 2020, when there were 4,293 confirmed cumulative deaths. By May 17, 2020 this number increased to 315,005. The risk of death is higher above the age of 60, but there are many deaths below 60 (for example, in Sao Paulo, 25%). Due to the lack of a vaccine or specific treatment, there are at least three types of interventions used in the first wave of this pandemic: increased alertness and hygiene (e.g. Sweden);identification and isolation of infected people and their contacts (e.g. South Korea);lockdown (e.g. Italy). These interventions are complementary. Choices of the right mix of interventions will vary from society to society and in the same society at different times. The search for a miracle drug is dangerous because it is based on the mistaken belief that any treatment option is better than "nothing". Brazilian society will not be able to maintain lockdown for a long period. Naturally, in the near future, regardless of the advice from scientists, doctors and authorities, commerce, services and schools will reopen. In order to implement any strategy aimed to control the pandemic and preserve the economy, the country needs leadership that centralizes and coordinates actions. Unfortunately, the Brazilian government is not fulfilling this role;on the contrary, it is a hindrance. This negative leadership and lack of coordination are causing many deaths and are severely damaging the lives of survivors by delaying the resuming of economic and social activities.

Strategies to deal with the COVID-19 pandemic.

The World Health Organization declared a COVID-19 pandemic on March 11, 2020, when there were 4,293 confirmed cumulative deaths. By May 17, 2020 this number increased to 315,005. The risk of death is higher above the age of 60, but there are many deaths below 60 (for example, in Sao Paulo, 25%). Due to the lack of a vaccine or specific treatment, there are at least three types of interventions used in the first wave of this pandemic: increased alertness and hygiene (e.g. Sweden); identification and isolation of infected people and their contacts (e.g. South Korea); lockdown (e.g. Italy). These interventions are complementary. Choices of the right mix of interventions will vary from society to society and in the same society at different times. The search for a miracle drug is dangerous because it is based on the mistaken belief that any treatment option is better than "nothing". Brazilian society will not be able to maintain lockdown for a long period. Naturally, in the near future, regardless of the advice from scientists, doctors and authorities, commerce, services and schools will reopen. In order to implement any strategy aimed to control the pandemic and preserve the economy, the country needs leadership that centralizes and coordinates actions. Unfortunately, the Brazilian government is not fulfilling this role; on the contrary, it is a hindrance. This negative leadership and lack of coordination are causing many deaths and are severely damaging the lives of survivors by delaying the resuming of economic and social activities.