Computed tomography angiography (CTA) is an effective tool to
determine the presence and severity of peripheral arterial disease
(PAD) in patients with intermittent claudication, according to the
results of a systematic review and meta-analysis reported in the
January 28 issue of the Journal of the American Medical Association.

"...CTA is an increasingly attractive imaging modality for assessing
lower extremity...PAD," write Rosemarie Met, MD, from Academic
Medical Center in Amsterdam, the Netherlands, and colleagues. "The
purpose of this systematic review and meta-analysis was to determine
the diagnostic performance of CTA compared with intra-arterial DSA
[digital subtraction angiography] for grading disease severity in
patients with PAD."

The reviewers searched MEDLINE from January 1966 through August 2008,
EMBASE from January 1980 through August 2008, and the Database of
Abstracts of Reviews of Effectiveness to identify studies that
compared the accuracy of CTA vs intra-arterial DSA to differentiate
the extent of PAD.

Inclusion criteria were comparison of multidetector CTA vs intra-
arterial DSA; study sample of at least 10 patients with intermittent
claudication or critical limb ischemia; testing looking for more than
50% stenosis or arterial occlusion; and presentation of either 2 x 2
or 3 x 3 contingency tables (¡Ü 50% stenosis vs > 50% stenosis or
occlusion), or provision of data allowing construction of these
tables.

Two reviewers screened studies to determine if they met inclusion
criteria and independently extracted study data. They also evaluated
methodologic quality using the quality assessment tool for diagnostic
accuracy studies (QUADAS) instrument.

Twenty (2.2%) of 909 studies identified met inclusion criteria;
median sample size in these was 33 (range, 16 - 279), and
methodologic quality was moderate. Of the total number of 957
patients enrolled, 68% had intermittent claudication.

For detection of more than 50% stenosis or occlusion, the overall
sensitivity of CTA was 95% (95% confidence interval [CI], 92% - 97%),
and specificity was 96% (95% CI, 93% - 97%). CTA accurately
identified occlusions in 94% of segments, the presence of more than
50% stenosis in 87% of segments, and the absence of significant
stenosis in 96% of segments. However, CTA overstaged 8% of segments
and understaged 15%.

"...CTA is an accurate modality to assess presence and extent of PAD
in patients with intermittent claudication; however, methodological
weaknesses of examined studies prevent definitive conclusions from
these data," the study authors write. "Nonetheless, CTA was a
reliable imaging modality with high sensitivity and specificity for
differentiating extent of disease in patients with predominantly
intermittent claudication compared with intra-arterial DSA."

Limitations of this study include exclusion of 12 studies because
they did not provide data allowing construction of 2 x 2 tables; the
possibility that important publications were missed; likely
publication bias; nonconsecutive recruitment and inclusion of only a
subset of stages of disease, resulting in possible spectrum bias;
only 4 studies clearly describing the selection criteria; incomplete
description of the patient population in many studies; most studies
including predominantly patients with intermittent claudication, who
are generally treated conservatively and do not typically require a
CTA; only 1 study including a large proportion of patients with
critical limb ischemia; and problems with the data analysis method in
the individual studies.

"Our meta-analysis also reveals that the diagnostic performance of
CTA for patients with critical limb ischemia has been poorly
investigated thus far," the review authors conclude. "More rigorous
evaluations of CTA in patients with critical limb ischemia are
needed."

The review authors have disclosed no relevant financial relationships.

JAMA. 2009;301:415-424.