Pm. Rothwell et al., Critical appraisal of the design and reporting of studies of imaging and measurement of carotid stenosis, STROKE, 31(6), 2000, pp. 1444-1450
Background and Purpose-Several hundred studies have been published over the
last few years on imaging and measurement of carotid stenosis. Despite all
this research, there is still no consensus about how best to image and mea
sure stenosis. One possible explanation for this is that many of the studie
s have not been large enough or methodologically sound enough to allow usef
ul conclusions to be drawn. We aimed to assess the design and methods of a
random sample of published studies of imaging and measurement of carotid st
enosis using 9 simple criteria.
Methods-A formal literature search was performed for studies of imaging and
measurement of carotid stenosis. Two subsets were randomly selected for de
tailed assessment: 20 studies published before 1991 and 20 published betwee
n 1993 and 1997 (some years after the initial publication of the ECST and N
ASCET trials). The criteria used to assess the selected studies were as fol
lows: prospective rather than retrospective study design; patient selection
based on a consecutive series or a random sample; adequate detail of study
population; adequate detail of imaging techniques; inclusion of all invest
igations, ie, patients with poor-quality imaging were not excluded; blinded
assessment of images; adequate detail of derivation of measurement of sten
osis from images or data; adequate data on the reproducibility of measureme
nts of stenosis; and study powered according to a sample-size calculation.
Results-There were many basic methodological deficiencies in both subsets o
f studies, with relatively little evidence of improvement with time. For ex
ample, only 33% of studies were prospective, only 45% studied a consecutive
or random selection of patients, and only 38% reported any data on the rep
roducibility of measurements. More than half of the studies satisfied less
than or equal to 4 of the 9 quality criteria. However, there was considerab
le variation between studies, with 7 studies satisfying greater than or equ
al to 7 criteria and 10 studies satisfying less than or equal to 2. No stud
y was based on a sample-size calculation. The number of patients studied wa
s often small, particularly in the more recent studies: median sample size
was 100 in the 1970-1990 studies and 58 in the 1993-1997 studies (P<0.0001)
.
Conclusions-The design and reporting of published studies of imaging and me
asurement of carotid stenosis are poor and have not improved much in recent
years. The majority of published studies are not of a sufficient standard
to enable the results to be used to inform clinical practice. The utility o
f future studies could be improved considerably by better adherence to 9 si
mple methodological guidelines.