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Evidence
Levels of evidence
The key recommendations
and levels of evidence incorporated
in the COPDX guidelines were
originally based
largely on the Global Initiative for
Chronic Obstructive Lung Disease
(GOLD), which used the evidence ranking system of the US National Heart,
Lung and Blood Institute (NHLBI).6
The NHLBI scheme is shown in Box 1. For comparison, the National Health and Medical Research Council
(NHMRC)5 levels of
evidence are also shown, along with the equivalent NHLBI categories.
For this update, the COPD Evaluation Committee reclassified
NHLBI level A as NHMRC level I and NHLBI level B as NHMRC level II evidence.
All citations to NHLBI level C were individually reviewed and reclassified
as NHMRC level II, III-2, III-3 or IV evidence. On closer examination, some
references originally classified as level C were actually considered level
D. As NHLBI level D is not recognised in the NHMRC classification, these
levels were removed whilst the bibliographic citations were retained.
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Box 1: Levels of evidence
a) National Heart, Lung, and Blood Institute (NHLBI)
categories
| NHLBI category |
Sources of evidence |
Definition |
|
| A |
Randomised controlled trials (RCTs).
Rich body of data. |
Evidence is from endpoints of
well-designed RCTs that provide a consistent pattern of findings in
the population for which the recommendation is made. Category A
requires substantial numbers of studies involving substantial
numbers of participants. |
| B |
Randomised controlled trials (RCTs).
Limited body of data. |
Evidence is from endpoints of
intervention studies that include only a limited number of patients,
postop or sub-group analysis of RCTs, or meta-analysis of RCTs. In
general, Category B pertains when few randomised trials exist, they
are small in size, they were undertaken in a population that differs
from the target population of the recommendation, or the results are
somewhat inconsistent. |
| C |
Non randomised trials. Observational
studies. |
Evidence is from outcomes of
uncontrolled or non randomised trials or from observational studies. |
| D |
Panel consensus Judgment. |
This category is used only in cases
where the provision of some guidance was deemed valuable but the
clinical literature addressing the subject was deemed insufficient
to justify placement in one of the other categories. The Panel
Consensus is based on clinical experience or knowledge that does not
meet the above-listed criteria. |
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b) National Health and Medical Research Council (NHMRC) levels
of evidence and corresponding National Heart, Lung, and Blood Institute
categories
|
NHLBI category |
NHMRC level |
Basis of Evidence |
|
| A |
I |
Evidence obtained from a systematic
review of all relevant randomised controlled trials |
| B |
II |
Evidence obtained from at least one
properly designed randomised controlled trial |
| C |
III - 1 |
Evidence obtained from well-designed
pseudorandomised controlled trials (alternate allocation or some
other method) |
| C |
III - 2 |
Evidence obtained from comparative
studies (including systematic reviews of such studies) with
concurrent controls and allocation not randomised, cohort studies,
case-control studies, or interrupted time series with a control
group |
| C |
III - 3 |
Evidence obtained from comparative
studies with historical control, two or more single arm studies, or
interrupted time series without a parallel group |
| C |
IV |
Evidence obtained from case series,
either post-test or pretest/ post-test |
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Content last updated: |
March 14, 2008 |
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Page
last updated: |
March 14, 2008 |
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