| dc.description.abstract | Background
Timely and accurate identification of ‘GCA-PMR Spectrum Disease’ and its
subsets is important so vascular complications can be averted. Traditional
diagnostic and monitoring tools such as Temporal Artery Biopsy (TAB) and serum
biomarkers have many shortcomings. Vascular Ultrasound (VUS) is superseding
TAB for diagnosis but its role in disease monitoring is unclear. Few studies have
evaluated the prevalence and natural history of Subclinical Giant Cell Arteritis
(GCA) in Polymyalgia Rheumatica (PMR).
Methods
VUS was performed in newly diagnosed GCA and PMR patients and a subset of
patients had TAB and Superficial Temporal Artery (STA) Magnetic Resonance
Angiography (MRA). Pre-Test Probability Score (PTPS), classification criteria and
VUS quantification scores were applied to the cohort. In those with a positive
baseline scan, VUS was repeated at 1, 3, 6 and 12 months. Clinical diagnosis was
verified by two rheumatologists and confirmed at 6 months.
Results
In 124 patients with GCA, VUS outperformed TAB and MRA STA for a clinical
diagnosis of GCA. Sensitivities (sens), specificities (spec) and ‘Area Under Curve’
(AUC) were as follows; VUS- 82.76%, 84.68%, 0.85; TAB- 40.4%, 100%, 0.70;
MRA- 47.1%, 20.0%, 0.35. PTPS improved the performance of VUS, achieving an
AUC 0.91 when used in combination with VUS. When PTPS 16 and VUS was
positive, specificity for GCA diagnosis was 100%. When PTPS 6 and VUS was
negative, sensitivity for GCA diagnosis was 100%. 2022 ACR/EULAR GCA
Classification Criteria had a better sensitivity and AUC than 1990 criteria but were
less specific for GCA diagnosis (sensitivities 92.4% and 72.7%, specificities 63.8%
and 69.1%, AUCs 0.78 and 0.70, respectively). Intima-Media Thickness (IMT) cut-
off points in this cohort differed from the currently accepted normal values.
Incorporating IMT measurement into the VUS protocol substantially improved its
diagnostic performance. Using the Right Frontal STA as an example; IMTmax
<0.15mm had 100% sensitivity for GCA, IMTmax >0.46mm had 100% specificity
for GCA. VUS quantification scores (Halo Count (HC), Halo Score (HS) and
OMERACT GCA US Score (OGUS)) declined over follow-up and baseline values
were more predictive of future adverse events than were all other patient variables.
OGUS demonstrated the most sensitivity to change. VUS had 83% sensitivity for
detecting Subclinical GCA in PMR, the prevalence of which was 24%, and these
patients were likelier to require biologic therapy.
Conclusions
VUS is confirmed as the optimal diagnostic test for GCA and TAB lacks sensitivity
for this purpose. PTPS has a role in evaluating suspected GCA when used in
combination with VUS. 2022 ACR/EULAR Classification Criteria are more sensitive
than 1990 criteria but lack adequate specificity to be used in clinical practice as
diagnostic criteria. MRA of STA lacked sensitivity and specificity for GCA.
Measuring IMT has a clear role in diagnosing GCA and allows for monitoring of
longitudinal trends in sonographic inflammation using VUS quantification scores, of
which OGUS appears the best. VUS quantification scores are more predictive of
future adverse events than all other patient variables. >20% of newly-diagnosed
PMR patients have Subclinical GCA. This appears to be a phenotypically distinct
subset of GCA, can be accurately identified by VUS and these patients are likely to
require biologic therapy. | en |
