14
Management
Aggregate Grades of Evidence by Question Type
a
Grade
a
Treatment Diagnosis Prognosis
A
Systematic review
b
of
randomized trials
Systematic review
b
of
cross-sectional studies
with consistently applied
reference standard and
blinding
Systematic review
b
of inception cohort
studies
c
B Randomized trials, or
observational studies
with dramatic effects
or highly consistent
evidence
Cross-sectional studies
with consistently applied
reference standard and
blinding
Inception cohort
studies
c
C Nonrandomized or
historically controlled
studies, including
case-control and
observational studies
Nonconsecutive studies,
case-control studies,
or studies with poor,
nonindependent, or
inconsistently applied
reference standards
Cohort study, control
arm of a randomized
trial, case series, or
case-control studies;
poor quality prognostic
cohort study
D Case reports, mechanism-based reasoning, or reasoning from first principles
X Exceptional situations where validating studies cannot be performed and there
is a clear preponderance of benefit over harm
OCEBM, Oxford Centre for Evidence-Based Medicine.
a
Adapted from Howick and colleagues.
b
A systematic review may be downgraded to level B because of study limitations, heterogeneity, or
imprecision.
c
A group of individuals identified for subsequent study at an early, uniform point in the course of
the specified health condition, or before the condition develops.
10
days
3-5
days
3-5
days
Sx
Onset
Dx
Initial
Abx
Change
Abx
KAS 4: Watchful
waiting for 3-5 days
KAS 6: If worsening or no
improvement after 3-5
days, change antibiotics
KAS 5: If no
improvement,
start antibiotics
Abx: Antibiotics
Dx: Initial Diagnosis
Initial Abx: Initial Antibiotics
Sx: Symptoms
Figure 6. Timeline of Watchful Waiting
