The U.S. Preventive Services Task Force (USPSTF) grades its recommendations
(A, B, C, D, or I) and the quality of the overall evidence for a service (good,
fair, poor). The definitions of these grades can be found at the end of the
"Major Recommendations" field.
The USPSTF concludes that the evidence
is insufficient to recommend for or against routine screening for dementia in
older adults. I recommendation.
The USPSTF found good evidence that some screening
tests have good sensitivity but only fair specificity in detecting cognitive
impairment and dementia. There is fair to good evidence that several drug
therapies have a beneficial effect on cognitive function (equivalent to delaying
the natural progression of Alzheimer's disease from 2 to 7 months), but the
evidence of their beneficial effects on instrumental activities of daily living
is mixed, with the benefit being small, at best. There is insufficient evidence
to determine whether the benefits observed in drug trials are generalizable to
patients whose disease would be detected by screening in primary care settings.
The accuracy of diagnosis, the feasibility of screening and treatment in routine
clinical practice, and the potential harms of screening (e.g., labeling effects)
are also unknown. The Task Force therefore could not determine whether the
benefits of screening for dementia outweigh the harms.
Clinical Considerations
- The Mini-Mental Status Examination (MMSE) is
the best-studied instrument for screening for cognitive impairment. When the
MMSE is used to screen unselected patients, the predictive value of a
positive result is only fair. The accuracy of the MMSE depends upon a person's age
and educational level: using an arbitrary cut-point may potentially lead to
more false-positives among older people with lower educational levels, and
more false-negatives among younger people with higher educational levels.
Tests that assess functional limitations rather than cognitive impairment, such
as the Functional Activities Questionnaire, can detect dementia with
sensitivity and specificity comparable to that of the MMSE.
- Early recognition of cognitive impairment, in
addition to helping make diagnostic and treatment decisions, allows clinicians
to anticipate problems the patients may have in understanding and adhering to
recommended therapy. This information may also be useful to the patient's
caregiver(s) and family member(s) in helping to anticipate and plan for future
problems that may develop as a result of progression of cognitive impairment.
- Although current evidence does not support routine screening of patients
in whom cognitive impairment is not otherwise suspected, clinicians should
assess cognitive function whenever cognitive impairment or deterioration is
suspected, based on direct observation, patient report, or concerns raised by
family members, friends, or caretakers.
Definitions:
The Task Force grades its
recommendations according to
one of 5 classifications (A, B, C, D, I) reflecting the strength of evidence and
magnitude of net benefit (benefits minus harms):
A
The USPSTF strongly recommends that clinicians provide [the
service] to eligible patients. The USPSTF found good evidence that [the service]
improves important health outcomes and concludes that benefits substantially
outweigh harms.
B
The USPSTF recommends that clinicians provide [this service] to
eligible patients. The USPSTF found at least fair evidence that [the service]
improves important health outcomes and concludes that benefits outweigh harms.
C
The USPSTF makes no recommendation for or against routine provision of [the
service]. The USPSTF found at least fair evidence that [the service] can improve
health outcomes but concludes that the balance of benefits and harms is too
close to justify a general recommendation.
D
The USPSTF recommends against routinely providing [the service] to
asymptomatic patients. The USPSTF found at least fair evidence that [the
service] is ineffective or that harms outweigh benefits.
I
The USPSTF concludes that the evidence is insufficient to recommend for
or against routinely providing [the service]. Evidence that [the service] is
effective is lacking, of poor quality, or conflicting and the balance of
benefits and harms cannot be determined.
The Task Force grades the quality of the overall evidence
for a service on a 3-point scale (good, fair, poor):
Good
Evidence includes consistent results from well-designed,
well-conducted studies in representative populations that directly assess
effects on health outcomes.
Fair
Evidence is sufficient to determine effects
on health outcomes, but the strength of the evidence is limited by the number,
quality, or consistency of the individual studies, generalizability to routine
practice, or indirect nature of the evidence on health outcomes.
Poor
Evidence
is insufficient to assess the effects on health outcomes because of limited
number or power of studies, important flaws in their design or conduct, gaps in
the chain of evidence, or lack of information on important health outcomes.