Comparing Semiquantitative and Qualitative Methods of Vascular 18F-FDG PET Activity Measurement in Large-Vessel Vasculitis.

The study rationale was to assess the performance of qualitative and semiquantitative scoring methods for 18F-FDG PET assessment in large-vessel vasculitis. Methods: Patients with giant cell arteritis or Takayasu arteritis underwent independent clinical and imaging assessments within a prospective observational cohort. 18F-FDG PET/CT scans were interpreted for active vasculitis by central reader assessment. Arterial 18F-FDG uptake was scored by qualitative visual assessment using the PET vascular activity score (PETVAS) and by semiquantitative assessment using SUVs and target-to-background ratios (TBRs) relative to liver or blood activity. The performance of each scoring method was assessed by intrarater reliability using the intraclass correlation coefficient (ICC) and areas under the receiver-operating-characteristic curve, applying physician assessment of clinical disease activity and reader interpretation of vascular PET activity as independent reference standards. The Wilcoxon signed-rank test was used to analyze change in arterial 18F-FDG uptake over time. Results: Ninety-five patients (giant cell arteritis, 52; Takayasu arteritis, 43) contributed 212 18F-FDG PET studies. The ICC for semiquantitative evaluation (0.99 [range, 0.98-1.00]) was greater than the ICC for qualitative evaluation (0.82 [range, 0.56-0.93]). PETVAS and target-to-background ratio metrics were more strongly associated with reader interpretation of PET activity than SUV metrics. All assessment methods were significantly associated with physician assessment of clinical disease activity, but the semiquantitative metric liver tissue-to-background ratio (TBRLiver) achieved the highest area under the receiver-operating-characteristic curve (0.66). Significant but weak correlations with C-reactive protein were observed for SUV metrics (r = 0.19, P < 0.01) and TBRLiver (r = 0.20, P < 0.01) but not for PETVAS. In response to increased treatment in 56 patients, arterial 18F-FDG uptake was significantly reduced when measured by semiquantitative (TBRLiver, 1.31-1.23; 6.1% change; P < 0.0001) or qualitative (PETVAS, 22-18; P < 0.0001) methods. Semiquantitative metrics provided information complementary to qualitative evaluation in cases of severe vascular inflammation. Conclusion: Both qualitative and semiquantitative methods of measuring arterial 18F-FDG uptake are useful in assessing and monitoring vascular inflammation in large-vessel vasculitis. Compared with qualitative metrics, semiquantitative methods have superior reliability and better discriminate treatment response in cases of severe inflammation.

Utility of the Brief Illness Perception Questionnaire to Monitor Patient Beliefs in Systemic Vasculitis.

OBJECTIVE: To assess the validity and clinical utility of the Brief Illness Perception Questionnaire (BIPQ) to measure illness perceptions in multiple forms of vasculitis. METHODS: Patients with giant cell arteritis (GCA), Takayasu arteritis (TA), antineutrophil cytoplasmic antibody-associated vasculitis (AAV), and relapsing polychondritis (RP) were recruited into a prospective, observational cohort. Patients independently completed the BIPQ, Multidimensional Fatigue Inventory (MFI), Medical Outcomes Study 36-item Short Form survey (SF-36), and a patient global assessment (PtGA) at successive study visits. Physicians concurrently completed a physician global assessment (PGA) form. Illness perceptions, as assessed by the BIPQ, were compared to responses from the full-length Revised Illness Perception Questionnaire (IPQ-R) and to other clinical outcome measures. RESULTS: There were 196 patients (GCA = 47, TA = 47, RP = 56, AAV = 46) evaluated over 454 visits. Illness perception scores in each domain were comparable between the BIPQ and IPQ-R (3.28 vs 3.47, P = 0.22). Illness perceptions differed by type of vasculitis, with the highest perceived psychological burden of disease in RP. The BIPQ was significantly associated with all other patient-reported outcome measures (rho = |0.50-0.70|, P < 0.0001), but did not correlate with PGA (rho = 0.13, P = 0.13). A change in the BIPQ composite score of ≥ 7 over successive visits was associated with concomitant change in the PtGA. Change in the MFI and BIPQ scores significantly correlated over time (rho = 0.38, P = 0.0008). CONCLUSION: The BIPQ is an accurate and valid assessment tool to measure and monitor illness perceptions in patients with vasculitis. Use of the BIPQ as an outcome measure in clinical trials may provide complementary information to physician-based assessments.

Outcome Measures in Large Vessel Vasculitis: Relationship Between Patient-, Physician-, Imaging-, and Laboratory-Based Assessments.

OBJECTIVE: To assess the relationship between measures of disease assessment in patients with large vessel vasculitis. METHODS: Patients with giant cell arteritis (GCA) or Takayasu arteritis (TAK) were recruited into a prospective, observational cohort. Assessments within the following outcomes were independently recorded: 1) patient-reported outcomes (Multidimensional Fatigue Inventory, patient global assessment of disease activity [PtGA], Short Form 36 health survey [SF-36], Brief Illness Perception Questionnaire), 2) physician global assessment of disease activity (PhGA), 3) laboratory outcomes (C-reactive protein [CRP] level, erythrocyte sedimentation rate [ESR]), and 4) imaging outcomes (PETVAS, a qualitative score of vascular 18 F-fluorodeoxyglucose-positron emission tomography activity). RESULTS: Analyses were performed on 112 patients (GCA = 56, TAK = 56), over 296 visits, with a median follow-up of 6 months. Correlation network analysis revealed assessment measures clustered independently by type of outcome. PhGA was centrally linked to all other outcome types, but correlations were modest (ρ = 0.12-0.32; P < 0.05). PETVAS, CRP level, and PtGA were independently associated with clinically active disease. All 4 patient-reported outcomes strongly correlated with each other (ρ = 0.35-0.60; P < 0.0001). Patient-reported outcomes were not correlated with PETVAS, and only PtGA correlated with CRP level (ρ = 0.16; P < 0.01). Patients whose clinical assessment changed from active disease to remission (n = 29) had a corresponding significant decrease in ESR, CRP level, and PETVAS at the remission visit. Patients whose clinical assessment changed from remission to active disease (n = 11) had a corresponding significant increase in CRP level and PtGA at the active visit. CONCLUSION: Measures of disease assessment in large vessel vasculitis consist of independent, yet complementary, outcomes, supporting the need to develop composite outcome measures or a standard set of measures covering multiple types of outcomes.

Clinical symptoms and associated vascular imaging findings in Takayasu's arteritis compared to giant cell arteritis.

OBJECTIVE: To compare the presence of head, neck and upper extremity symptoms in patients with Takayasu's (TAK) and giant cell arteritis (GCA) and their association with vascular inflammation assessed by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) or arterial damage assessed by magnetic resonance angiography (MRA). METHODS: Patients with TAK and GCA underwent clinical and imaging assessments within 24 hours, blinded to each other. Vascular inflammation was defined as arterial FDG-PET uptake greater than liver by visual assessment. Arterial damage was defined as stenosis, occlusion, or aneurysm by MRA. Clinically reported symptoms were compared with corresponding imaging findings using generalised mixed model regression. Cranial symptoms were studied in association with burden of arterial disease in the neck using ordinal regression. RESULTS: Participants with TAK (n=56) and GCA (n=54) contributed data from 270 visits. Carotidynia was reported only in patients with TAK (21%) and was associated with vascular inflammation (p<0.01) but not damage (p=0.33) in the corresponding carotid artery. Posterior headache was reported in TAK (16%) and GCA (20%) but was only associated with corresponding vertebral artery inflammation and damage in GCA (p<0.01). Arm claudication was associated with subclavian artery damage (p<0.01) and inflammation (p=0.04) in TAK and with damage in GCA (p<0.01). Patients with an increased burden of damaged neck arteries were more likely to experience positional lightheadedness (p<0.01) or a major central nervous system event (p=0.01). CONCLUSION: The distribution of symptoms and association with imaging abnormalities differs in patients with TAK and GCA. These findings may help clinicians predict associated FDG-PET and MRA findings based on a specific clinical symptom. CLINICAL TRIAL REGISTRATION NUMBER: NCT02257866.

Imaging acquisition technique influences interpretation of positron emission tomography vascular activity in large-vessel vasculitis.

OBJECTIVES: To determine the impact of imaging acquisition time on interpretation of disease activity on 18F-fluorodeoxyglucose positron emission tomography (PET) in large-vessel vasculitis (LVV) and assess the relationship between clinical features and image acquisition time. METHODS: Patients with giant cell arteritis (GCA) and Takayasu's arteritis (TAK) were recruited into a prospective, observational cohort. After a single injection of FDG, all patients underwent two sequential PET scans at one and two-hour time points. Images were interpreted for active vasculitis by subjective assessment, qualitative assessment, and semi-quantitative assessment. Agreement was assessed by percent agreement, Cohen's kappa, and McNemar's test. Multivariable logistic regression identified associations between PET activity and clinical variables. RESULTS: 79 patients (GCA  =  44, TAK  =  35) contributed 168 paired one and two-hour PET studies. A total of 94 out of 168 scans (56%) were interpreted as active at the one-hour time point, and 129 scans (77%) were interpreted as active at the two-hour time point (p < 0.01). Associations between clinical variables and PET activity categories (dual inactive, delayed active, dual active) were evaluated. Using multivariable nominal regression, clinically active disease was significantly more common in patients in the delayed active group (Odds Ratio 1.94, 95%CI 1.13-3.53; p  =  0.02) and the dual active group (Odds Ratio 1.71, 95%CI 1.06-2.93; p  =  0.04) compared to the dual inactive group. CONCLUSIONS: Imaging protocol significantly influences interpretation of PET activity in LVV. A substantial proportion of patients with LVV have PET activity only detected by delayed imaging. These patients were significantly more likely to have concomitant clinically-determined active disease.

Effect of Treatment on Imaging, Clinical, and Serologic Assessments of Disease Activity in Large-vessel Vasculitis.

OBJECTIVE: Disease activity in large-vessel vasculitis (LVV) is traditionally assessed by clinical and serological variables rather than vascular imaging. This study determined the effect of treatment on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) vascular activity in relation to clinical- and serologic-based assessments. METHODS: Patients with giant cell arteritis (GCA) or Takayasu arteritis (TA) were prospectively evaluated at 6-month intervals in an observational cohort. Treatment changes were made at least 3 months before the followup visit and categorized as increased, decreased, or unchanged. Imaging (FDG-PET qualitative analysis), clinical, and serologic (erythrocyte sedimentation rate, C-reactive protein) assessments were determined at each visit and compared over interval visits. RESULTS: Serial assessments were performed in 52 patients with LVV (GCA = 31; TA = 21) over 156 visits. Increased, decreased, or unchanged therapy was recorded for 36-, 23-, and 32-visit intervals, respectively. When treatment was increased, there was significant reduction in disease activity by imaging, clinical, and inflammatory markers (p ≤ 0.01 for each). When treatment was unchanged, all 3 assessments of disease activity remained similarly unchanged over 6-month intervals. When treatment was reduced, PET activity significantly worsened (p = 0.02) but clinical and serologic activity did not significantly change. Treatment of GCA with tocilizumab and of TA with tumor necrosis factor inhibitors resulted in significant improvement in imaging and clinical assessments of disease activity, but only rarely did the assessments both become normal. CONCLUSION: In addition to clinical and serologic assessments, vascular imaging has potential to monitor disease activity in LVV and should be tested as an outcome measure in randomized clinical trials.

Clinical Factors Associated with Time-Specific Distribution of 18F-Fluorodeoxyglucose in Large-Vessel Vasculitis.

18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can detect vascular inflammation in large-vessel vasculitis (LVV). Clinical factors that influence distribution of FDG into the arterial wall and other tissues have not been characterized in LVV. Understanding these factors will inform analytic strategies to quantify vascular PET activity. Patients with LVV (n = 69) underwent 141 paired FDG-PET imaging studies at one and two hours per a delayed image acquisition protocol. Arterial uptake was quantified as standardized uptake values (SUVMax). SUVMean values were obtained for background tissues (blood pool, liver, spleen). Target-to-background ratios (TBRs) were calculated for each background tissue. Mixed model multivariable linear regression was used to identify time-dependent associations between FDG uptake and selected clinical features. Clinical factors associated with FDG distribution differed in a tissue- and time-dependent manner. Age, body mass index, and C-reactive protein were significantly associated with arterial FDG uptake at both time points. Clearance factors (e.g. glomerular filtration rate) were significantly associated with FDG uptake in background tissues at one hour but were weakly or not associated at two hours. TBRs using liver or blood pool at two hours were most strongly associated with vasculitis-related factors. These findings inform standardization of FDG-PET protocols and analytic approaches in LVV.

Comparison of magnetic resonance angiography and 18F-fluorodeoxyglucose positron emission tomography in large-vessel vasculitis.

OBJECTIVES: To assess agreement between interpretation of magnetic resonance angiography (MRA) and 18F-fluorodeoxyglucose positron emission tomography (PET) for disease extent and disease activity in large-vessel vasculitis (LVV) and determine associations between imaging and clinical assessments. METHODS: Patients with giant cell arteritis (GCA), Takayasu's arteritis (TAK) and comparators were recruited into a prospective, observational cohort. Imaging and clinical assessments were performed concurrently, blinded to each other. Agreement was assessed by per cent agreement, Cohen's kappa and McNemar's test. Multivariable logistic regression identified MRA features associated with PET scan activity. RESULTS: Eighty-four patients (GCA=35; TAK=30; comparator=19) contributed 133 paired studies. Agreement for disease extent between MRA and PET was 580 out of 966 (60%) arterial territories with Cohen's kappa=0.22. Of 386 territories with disagreement, MRA demonstrated disease in more territories than PET (304vs82, p<0.01). Agreement for disease activity between MRA and PET was 90 studies (68%) with Cohen's kappa=0.30. In studies with disagreement, MRA demonstrated activity in 23 studies and PET in 20 studies (p=0.76). Oedema and wall thickness on MRA were independently associated with PET scan activity. Clinical status was associated with disease activity by PET (p<0.01) but not MRA (p=0.70), yet 35/69 (51%) patients with LVV in clinical remission had active disease by both MRA and PET. CONCLUSIONS: In assessment of LVV, MRA and PET contribute unique and complementary information. MRA better captures disease extent, and PET scan is better suited to assess vascular activity. Clinical and imaging-based assessments often do not correlate over the disease course in LVV. TRIAL REGISTRATION NUMBER: NCT02257866.