Factors that decrease the quality level of a body of evidence

We now describe in more detail the five reasons for downgrading the quality of a body of evidence for a specific outcome (Table 12.2.b). In each case, if a reason is found for downgrading the evidence, it should be classified as 'serious' (downgrading the quality rating by one level) or 'very serious' (downgrading the quality grade by two levels). 1. Limitations in the design and implementation Our confidence in an estimate of effect decreases if studies suffer from major limitations that are...

Transformations and skewed data

Summary statistics may be presented after a transformation has been applied to the raw data. For example, means and standard deviations of logarithmic values may be available (or, equivalently, a geometric mean and its confidence interval). Such results should be collected, as they may be included in meta-analyses, or - with certain assumptions -may be transformed back to the raw scale. For example, a trial reported meningococcal antibody responses 12 months after vaccination with meningitis C...

Box 64f Demonstration search strategy for Medline Ovid format for the topic Tamoxifen for breast cancer

1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 animals.sh. not (humans.sh. and animals.sh.) The 'adj6' operator indicates within six words ' ' indicates truncation .mp. indicates a search of title, original title, abstract, name of substance word and subject heading word. Non-Indexed Citations Month X, 200X' file. For further guidance on this issue, contact a Trials Search Co-ordinator.

References

Meta-analysis of heterogeneously reported trials assessing change from baseline. Statistics in Medicine 2005 24 3823-3844. Bauer 1991 Bauer P. Multiple testing in clinical trials. Statistics in Medicine 1991 10 871-889. Bender 2001 Bender R, Lange S. Adjusting for multiple testing - when and how Journal of Clinical Epidemiology 2001 54 343-349. Bender 2008 Bender R, Bunce C, Clarke M, Gates S, Lange S, Pace NL, Thorlund K. Attention should be given to...