Japanese Translation

Recommendations

The highest level of available evidence was used to form all the recommendations contained in this guideline. The evidence was graded using standard criteria shown below:

Hierarchy of evidence

Level	Evidence
1a	Systematic review and meta-analysis of randomised controlled trials (RCTs)
1b	At least one RCT
2a	At least one well-designed controlled study without randomisation
2b	At least one other type of well-designed quasi-experimental study
3	Well-designed, non-experimental, descriptive studies, such as comparative studies, correlation studies or case studies
4	Expert committee reports or opinions and/or clinical experience of respected authorities

This scale, which was developed to apply to studies about the effectiveness of health care interventions, is only a guide to the validity and relevance of evidence. Other questions may be more appropriately addressed by different study designs: for example, a question about the predictive power of an investigation is best answered with observational data.

Recommendations were based on, and linked to, the supporting evidence, or where necessary, the informal consensus of the working group. The strength of evidence corresponding to each level of recommendation is shown below. Regarding diagnostic tests specifically, a recommendation based on the existence of a well-conducted systematic review was assessed as Grade A.

Some recommendations were extrapolated from strong evidence relating to the management of dysmenorrhoea in women without confirmed endometriosis.

Grades of recommendations

A	Requires at least one randomised controlled trial as part of a body of literature of overall good quality and consistency addressing the specific recommendation. (Evidence levels 1a, 1b).
B	Requires the availability of well controlled clinical studies but no randomised clinical trials on the topic of recommendations. (Evidence levels 2a, 2b, 3).
C	Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates and absence of directly applicable clinical studies of good quality. (Evidence level 4).
GPP	Recommended best practice based on the clinical experience of the guideline development group.