Analyzing the Study of Using Acupuncture in Delivery in the Past Ten Years in China

Table 3

Oxford center for evidence-based medicine levels of evidence (March 2009).

Level	Therapy/prevention
1a	SR (with homogeneity^1) of RCTs
1b	Individual RCT (with narrow confidence interval^2)
1c	All of none^3
2a	SR (with homogeneity^1) of cohort studies
2b	Individual cohort study (including low quality RCT; e.g., <80% followup)
2c	Outcomes research; ecological studies
3a	SR (with homgeneity^1) of case control studies
3b	Individual case control study
4	Case series (and poor quality cohort and case control studies^4)
5	Expert opinion without explicit critical appraisal or based on physilolgy, bench research, or “first principles”

Notes: Produce by Phillips et al. [2], since November 1998. Updated by http://www.cebm.net/index.aspx?o=1025. Users can add a minus sign “−" to denote the level of that fails to provide a conclusive answer, because:
• EITHER a single result with a wide confidence interval;
• OR a Systematic Review with troublesome heterogeneity.
“Such evidence is inconclusive, and therefore can only generate Grade D recommendations”.
Grade D means: level 5 evidence or troublingly inconsistent or inconclusive studies of any level.
¹By homogeneity we mean a systematic review that is free of worrisome variations (heterogeneity) in the directions and degrees of results between individual studies. Not all systematic reviews with statistically significant heterogeneity need be worrisome and not all worrisome heterogeneity need be statistically significant. As noted above, studies displaying worrisome heterogeneity should be tagged with a “−” at the end of their designated level. ²See note above for advice on how to understand, rate and use trials or other studies with wide confidence intervals. ³Met when all patients died before the Rx became available, but some now survive on it; or when some patients died before the Rx became available, but none now dies on it. ⁴By poor quality cohort study we mean one that failed to clearly define comparison groups and/or failed to measure exposures and outcomes in the same (preferably blinded) objective way in both exposed and nonexposed individuals and/or failed to identify or appropriately control known confounders and/or failed to carry out a sufficiently long and complete followup with patients. By poor quality case control study we mean one that failed to clearly define comparison groups and/or failed to measure exposures and outcomes in the same (preferably blinded) objective way in both cases and controls and/or failed to identify or appropriately control known confounders.