Irvine 1998.

Study characteristics
Methods	Parallel group, single centre RCT No. of women randomised: 44 No. of women analysed: 36 Exclusions post randomisation: 0. Withdrawal from treatment: 3 months ‒ 2 from LNG group and 6 from Norethisterone group Power calculation for sample size was performed Both ITT (for primary outcome) and per protocol analysis performed Source of funding: not stated
Participants	Country: UK Women aged 18 to 45 years all referred to specialist clinic complaining of regular heavy menstrual bleeding 151 women were screened but 197 were excluded from eligibility (41 measured menstrual blood loss < 80 mL; 62 declined to do menstrual blood loss measurements; 4 declined to participate) Inclusion criteria > 80 mL/cycle loss (as measured by alkaline haematin method) Parous (1 or more children) Normal pelvic examination Negative cervical cytology Regular menstrual cycle Good general health Uterine cavity sound length less than 10 cm Exclusion criteria Abnormal pelvic examination Recent use of oestrogens, progestogens or anticoagulants (within 3 months) Injectable hormones for contraception (within 12 months).
Interventions	(1) Levonorgestrel‐releasing (20 µg/day) intrauterine contraceptive system inserted within 7 days of menstruation (2) Norethisterone 5 mg ×3 daily taken on Day 5 to 26 of the menstrual cycle for 3 cycles Duration: 3 months
Outcomes	Primary Menstrual blood loss (alkaline haematin method) at 3 months' follow‐up Secondary Hb and serum Fe at pretreatment and 3 months (or sooner if premature termination) Participant symptom/side effect questionnaire at pretreatment, 1 and 3 months Participant satisfaction categorised as liking treatment very well, well, moderately, poorly Women were asked how their periods interfered with their quality of life both before and after treatment Proportion of women with amenorrhoea Proportion of women with specified side effects Withdrawal from treatment because of adverse events relating to treatment Acceptability of treatment (willingness to continue)
Notes	Outcomes assessed at 3 months, which is relatively short period to assess the effectiveness of the LNG‐IUS Power calculation performed prior to commencement of trial to assess group size and ITT analysis of data
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "computer generated"
Allocation concealment (selection bias)	Low risk	Quote: "sealed opaque consecutively numbered envelopes"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded, lack of blinding likely to influence outcome
Blinding of participants and personnel (performance bias) Haematin alkaline, Haemoglobin All outcomes	Low risk	No blinding, lack of blinding unlikely to influence outcome
Blinding of outcome assessment (detection bias) All outcomes	High risk	Not blinded, lack of blinding likely to influence outcome
Blinding of outcome assessment (detection bias) (Haematine alkaline and haemoglobin) All outcomes	Low risk	No blinding, lack of blinding unlikely to influence outcome
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Authors stated that both ITT and per protocol analyses were performed but it appears that this was only for menstrual blood loss and satisfaction. Per protocol analyses were undertaken for all other outcomes. Completers of the trial at 3 months were 20/22 (90.9%) in LNG group and 16/22 (72.7%) in NET group. Side effects were collected in only 12/22 (54.5%) of NET group
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported
Other bias	Low risk	Groups appeared similar at baseline