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Table 2 Level of certainty regarding the net benefit

From: Abdominal hysterectomy for benign indications: evidence-based guidance for surgical decisions

Level of certainty

Description

High

The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects on the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies.

Moderate

The available evidence is sufficient to determine the effect of the preventive service on health outcomes, but confidence in the estimate is constrained by such factors as:

• The number, size or quality of individual studies.

• Inconsistency of findings across individual studies

• Limited generalizability of findings to routine primary care practice

• Lack of coherence in the chain of evidence

As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion

Low

The available evidence is insufficient to assess effect on health outcome. Evidence is insufficient because of:

• The number or size of studies

• Important flaws in study design or methods

• Inconsistency of findings across individual studies

• Gaps in the chain of evidence

• Finding not generalizable to routine primary care practice

• Lack of information on important health outcomes

More information may allow estimation of effects on health outcomes.