Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Pain
Systematic review	21 women with primary dysmenorrhoea Data from 1 RCT	Proportion of women with pain relief measured by subjective assessment 16/21 (76%) with high-frequency TENS 9/21 (43%) with low-frequency TENS	OR 3.9 95% CI 1.1 to 13.0	Moderate effect size	high-frequency TENS
Need for additional medication
Systematic review	24 women with primary dysmenorrhoea Data from 1 RCT	Mean number of additional analgesic tablets taken 6.9 with high-frequency TENS 3.7 with low-frequency TENS	WMD 3.2 tablets 95% CI 0.5 tablets to 5.9 tablets Randomisation and blinding unclear	Effect size not calculated	low-frequency TENS