Summary of findings 2. Intermittent iron supplementation versus daily iron supplementation in menstruating women.
| Intermittent iron supplementation versus daily iron supplementation in menstruating women | ||||||
| Patient or population: adolescent and adult menstruating women Setting: community settings Intervention: intermittent iron supplementation alone or with any other micronutrients Comparison: daily iron supplementation alone or with any other micronutrients | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with daily iron supplementation | Risk with intermittent iron supplementation | |||||
| Anaemia (haemoglobin concentration below a cut‐off defined by the trialists, adjusted by altitude and smoking as appropriate) Follow‐up: range 2 months to 4 months | Study population | RR 1.09 (0.93 to 1.29) | 1749 (8 studies) | ⊕⊕⊕⊝ Moderatea | Includes two cluster‐randomised trials* b | |
| 23 per 100 | 25 per 100 (22 to 30) | |||||
| Haemoglobin (g/L) Follow‐up: range 2 months to 1 year | The mean haemoglobin g/L in the control groups ranged from 7.40 g/L to 132.00 g/L | The mean haemoglobin g/L in the intervention groups was 0.43 g/L higher (1.44 lower to 2.31 higher) | ‐ | 2127 (10 studies) | ⊕⊕⊝⊝ Lowc | Includes two cluster‐randomised trials* b |
| Iron deficiency (as defined by the trialists using indicators of iron status such as ferritin or transferrin) Follow‐up: mean 3 months | Study population | RR 4.30 (0.56 to 33.20) | 198 (1 study) | ⊕⊝⊝⊝ Very lowd | ‐ | |
| 2 per 100 | 7 per 100 (1 to 52) | |||||
| Ferritin (µg/L) Follow‐up: range 2 months to 1 year | The mean ferritin µg/L in the control groups ranged from 16.70 µg/L to 62.00 µg/L | The mean ferritin µg/L in the intervention groups was 6.07 µg/L lower (10.66 lower to 1.48 lower) | ‐ | 988 (4 studies) | ⊕⊕⊝⊝ Lowe | Includes one cluster‐randomised trial b |
| Iron deficiency anaemia (as defined by the presence of anaemia plus iron deficiency, diagnosed with an indicator of iron status selected by the trialists) | Not estimable | ‐ | (0 studies) | ‐ | ‐ | |
| All‐cause morbidity (the most frequent event associated with the intervention, independent of the cause, as defined by the trialists) | Not estimable | ‐ | (0 studies) | ‐ | ‐ | |
| Any adverse side effects | 29 per 100 |
2 per 100 (6 to 24) |
RR 0.41 (0.21 to 0.82) |
1166 (6 studies) |
⊕⊕⊕⊝ Lowf | Includes one cluster‐randomised trial b |
| *The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk ratio | ||||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate quality: We are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low quality: Our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low quality: We have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect. | ||||||
aDowngraded one level due to study limitations (in several trials the method of allocation concealment was not clear and there was a lack of blinding) (I2 = 12%). bFor cluster‐randomised studies (C), the analyses only include the estimated effective sample size, after adjusting the data to account for the clustering effect. cDowngraded two levels due to inconsistency (in the direction of the effect and the CI of some of the included studies cross the line of no effect, and high heterogeneity) (I2 = 78%). dDowngraded two levels due to imprecision (only one study with 25 losses to follow‐up reported data on this outcome; wide CI) and one level for study limitations (concerns about attrition) (l2 = not estimable). eDowngraded two levels due to inconsistency (in the direction of the effect and the CI of some of the included studies cross the line of no effect, and high heterogeneity) (I2 = 91%). f Downgraded two levels due to inconsistency (in the direction of the effect and the CI of some of the included studies cross the line of no effect, and high heterogeneity) (I2 = 82%).