United states preventive services task force recommendations scheme

Grade: A

 * The USPSTF recommends the service.
 * There is high certainty that the net benefit is substantial.

Grade: B

 * The USPSTF recommends the service.
 * There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.

Grade: C

 * The USPSTF recommends against routinely providing the service.
 * There may be considerations that support providing the service in an individual patient.
 * There is moderate or high certainty that the net benefit is small.

Grade: D

 * The USPSTF recommends against the service.
 * There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.

Grade: I Statement

 * The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service.
 * Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined.

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

Level of Certainty: Moderate

 * The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by factors such 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.

Level of Certainty: Low

 * The available evidence is insufficient to assess effects on health outcomes.
 * Evidence is insufficient because of:
 * The limited number or size of studies
 * Important flaws in study design or methods
 * Inconsistency of findings across individual studies
 * Gaps in the chain of evidence
 * Findings not generalizable to routine primary care practice
 * A lack of information on important health outcomes


 * More information may allow an estimation of effects on health outcomes.

Resources
USPSTF Clinical Practice Guidelines