Evidence
This page contains a snapshot of featured content which highlights evidence addressing key clinical questions including areas of uncertainty. Please see the main topic reference list for details of all sources underpinning this topic.
BMJ Best Practice evidence tables
Evidence tables provide easily navigated layers of evidence in the context of specific clinical questions, using GRADE and a BMJ Best Practice Effectiveness rating. Follow the links at the bottom of the table, which go to the related evidence score in the main topic text, providing additional context for the clinical question. Find out more about our evidence tables.
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is moderate or low to moderate where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes.
Population: Children and infants aged 6 months and over living in settings where anaemia is highly prevalent
Intervention: Daily oral iron supplementation
Comparison: Placebo or control
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Children aged 6 to 23 months | ||
Anaemia (haemoglobin below a cut-off value determined by the trialists) | Favours intervention | Moderate |
Iron deficiency (measured using indicators of iron status such as ferritin or transferrin) | Favours intervention | Moderate |
Iron deficiency anaemia (presence of anaemia plus iron deficiency, diagnosed with an indicator of iron status selected by trialists) | Favours intervention | High |
Growth measures (stunting) | No statistically significant difference | Moderate |
Growth measures (wasting) | No statistically significant difference | Low |
Mortality (all cause, acute respiratory infections, diarrhoea, malaria) | No statistically significant difference | Low |
Children aged 24 to 59 months | ||
Anaemia | No statistically significant difference | Very low |
Iron deficiency | - | None of the studies identified by the review assessed this outcome |
Iron deficiency anaemia | - | None of the studies identified by the review assessed this outcome |
Growth measures (height Z-score) | No statistically significant difference | Low |
Growth measures (weight Z-score) | No statistically significant difference | Low |
Mortality | - | None of the studies identified by the review assessed this outcome |
Children aged 60 months and older | ||
Anaemia | Favours intervention | Moderate |
Iron deficiency | Favours intervention | Low |
Iron deficiency anaemia | Favours intervention | Moderate |
Growth measures (height Z-score) | Favours intervention | Moderate |
Growth measures (weight Z-score) | No statistically significant difference | Low |
Mortality | - | None of the studies identified by the review assessed this outcome |
Recommendations as stated in the source guideline Daily iron supplementation is recommended as a public health intervention in infants and young children aged 6–23 months, living in settings where anaemia is highly prevalent, for preventing iron deficiency and anaemia. Daily iron supplementation is recommended as a public health intervention in preschool-age children aged 24–59 months, living in settings where anaemia is highly prevalent, for increasing haemoglobin concentrations and improving iron status. Daily iron supplementation is recommended as a public health intervention in school-age children aged 60 months and older, living in settings where anaemia is highly prevalent, for preventing iron deficiency and anaemia.
Note The guideline development group noted that while no major harms were identified the evidence is lacking for gastrointestinal effects, potential toxic endpoints, and the impact of iron overload. The guideline states that the recommendations apply at a population level to areas where anaemia is highly prevalent (≥40% anaemia prevalence); they considered for an individual child diagnosed with anaemia the national guidelines for the treatment of anaemia should be followed.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is high or moderate to high where GRADE has been performed and the intervention is more effective/beneficial than the comparison for key outcomes.
Population: Infants and children aged 6 months to 18 years
Intervention: Daily oral iron supplementation
Comparison: Placebo
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Clinical malaria (fever >37.5 °C and any parasitaemia): all children | No statistically significant difference | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): children aged 6-23 months | Favours intervention | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): children aged 24-59 months | No statistically significant difference | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): children aged 60 months or older | No statistically significant difference | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): anaemic at baseline | No statistically significant difference | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): non-anaemic at baseline | No statistically significant difference | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): malaria-prevention and treatment programme available | Favours intervention | Moderate |
Clinical malaria (fever >37.5 °C and any parasitaemia): malaria-prevention and treatment programme not available or unclear | Favours comparison | Moderate |
Severe malaria (clinical malaria with high-grade parasitaemia) | Favours intervention | High |
All-cause mortality | No statistically significant difference | Moderate |
Recommendations as stated in the source guideline In malaria-endemic areas, the provision of iron supplementation in infants and children should be done in conjunction with public health measures to prevent, diagnose, and treat malaria (strong recommendation, high quality of evidence).
Note The guideline recommendation was based on the evidence that iron supplementation in malaria-endemic areas does not seem to increase the risk of clinical malaria (where a malaria prevention and treatment programme is available), decreases the risk of severe malaria, and does not increase the risk of death.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is moderate or low to moderate where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes.
Population: Menstruating adult women and adolescent girls (all settings)
Intervention: Daily oral iron supplementation
Comparison: Placebo or control
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Anaemia (haemoglobin below a cut-off value determined by the trialists) | Favours intervention | Moderate |
Iron deficiency (measured using indicators of iron status such as ferritin or transferrin) | Favours intervention | Moderate |
Iron deficiency anaemia (presence of anaemia plus iron deficiency, diagnosed with an indicator of iron status selected by trialists) | - | None of the studies identified by the review assessed this outcome |
Morbidity (malaria incidence and severity) | - | None of the studies identified by the review assessed this outcome |
Recommendations as stated in the source guideline Daily iron supplementation is recommended as a public health intervention in menstruating adult women and adolescent girls, living in settings where anaemia is highly prevalent (≥40% anaemia prevalence), for the prevention of anaemia and iron deficiency (strong recommendation, moderate quality of evidence).
Note The guideline development group noted that the cost of providing daily iron supplementation would be largely determined by operational challenges rather than the cost of the supplement. The guideline states that the resources and investment required to overcome these challenges should be considered when designing programmes to reach this population.
This evidence table is related to the following section/s:
Cochrane Clinical Answers
Cochrane Clinical Answers (CCAs) provide a readable, digestible, clinically focused entry point to rigorous research from Cochrane systematic reviews. They are designed to be actionable and to inform decision making at the point of care and have been added to relevant sections of the main Best Practice text.
- For children from low- and middle-income countries, does point-of-use fortification of foods with micronutrient powders improve outcomes?
- Can adding multiple micronutrients to food improve health in the general population?
- How does fortification of salt with iron plus iodine compare with fortification of salt with iodine alone for improving iron and iodine status in children, adolescents, and adults?
- Is there randomized controlled trial evidence to support the use of oral iron supplements (with or without folic acid) in children in malaria-endemic areas?
- How does intermittent compare with daily oral iron supplementation in pregnant women?
- How effective is intermittent iron supplementation for preventing and treating anemia and its associated impairments in menstruating women?
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