18F-fluorodeoxyglucose positron emission tomography in elderly patients with an elevated erythrocyte sedimentation rate of unknown origin

Systemic vasculitides and the role of multitechnique imaging in the diagnosis

Vasculitis, a systemic disease characterised by inflammation of the blood vessels, remains challenging to diagnose and manage. Vessel size has been the basis for classifying systemic vasculitides. Imaging plays a vital role in diagnosing this challenging disease. This review article aims (a) to summarise up-to-date literature in this field, as well as include classification updates and (b) to review available imaging techniques, recent advances, and emphasis on imaging findings to diagnose large vessel vasculitides.

Extremely Elevated Erythrocyte Sedimentation Rates: Associations With Patients' Diagnoses, Demographic Characteristics, and Comorbidities

OBJECTIVE

To study associations between extreme erythrocyte sedimentation rate (ESR) elevations (≥100 mm/h) and diseases, age, sex, race, Charlson Comorbidity Index (CCI), and C-reactive protein (CRP) level.

PATIENTS AND METHODS

This was a retrospective cohort study of 4807 patients with extreme ESR values examined at Mayo Clinic, Rochester, Minnesota, from January 1, 2002, through December 31, 2011. Independent variables included diseases (infection, autoimmune, malignancy, renal disease, or miscellaneous), subcategories of diseases, patient demographic characteristics (age, sex, and race), CRP level, and CCI. The Wilcoxon rank sum test was used to assess comparisons of ESR between patients with and without disease as well as relationships between extreme ESR values and demographic characteristics of patients within disease categories. Associations between ESR and CRP level were determined using the Pearson correlation coefficient.

RESULTS

The leading diagnosis associated with extreme ESR elevations (n [%]) was infection (1932 [40]), followed by autoimmune (1839 [38]) and malignancy (1736 [36]) (P<.01). Extreme elevations in ESR varied by sex, with higher ESRs in men (mean, 117±13.3 mm/h) than in women (mean, 115.9±12.5 mm/h) (P=.008). Extreme ESR elevations correlated inversely with the CCI (P=.008) and did not correlate with the CRP level. There were no correlations between extreme elevations in ESR and age or race.

CONCLUSION

We found that almost all patients have an identifiable etiology for extreme ESR elevations and that infection is the most common disease association. Unlike previous research, we identified higher ESRs in men than in women and no associations with age, race, and comorbid illness. These findings may enhance the diagnostic evaluation of patients with extreme ESR elevations.

The value of 18F-FDG-PET/CT in identifying the cause of fever of unknown origin (FUO) and inflammation of unknown origin (IUO): data from a prospective study

BACKGROUND

Fever of unknown origin (FUO) and inflammation of unknown origin (IUO) are diagnostically challenging conditions. Diagnosis of underlying disease may be improved by ¹⁸F-fluorodesoxyglucose positron emission tomography (¹⁸F-FDG-PET).

METHODS

Prospective study to test diagnostic utility of ¹⁸F-FDG-PET/CT in a large cohort of patients with FUO or IUO and to define parameters that increase the likelihood of diagnostic ¹⁸F-FDG-PET/CT. Patients with FUO or IUO received ¹⁸F-FDG-PET/CT scanning in addition to standard diagnostic work-up. ¹⁸F-FDG-PET/CT results were classified as helpful or non-helpful in establishing final diagnosis. Binary logistic regression was used to identify clinical parameters associated with a diagnostic ¹⁸F-FDG-PET/CT.

RESULTS

240 patients were enrolled, 72 with FUO, 142 with IUO and 26 had FUO or IUO previously (exFUO/IUO). Diagnosis was established in 190 patients (79.2%). The leading diagnoses were adult-onset Still's disease (15.3%) in the FUO group, large vessel vasculitis (21.1%) and polymyalgia rheumatica (18.3%) in the IUO group and IgG₄-related disease (15.4%) in the exFUO/IUO group. In 136 patients (56.7% of all patients and 71.6% of patients with a diagnosis), ¹⁸F-FDG-PET/CT was positive and helpful in finding the diagnosis. Predictive markers for a diagnostic ¹⁸F-FDG-PET/CT were age over 50 years (p=0.019), C-reactive protein (CRP) level over 30 mg/L (p=0.002) and absence of fever (p=0.001).

CONCLUSION

¹⁸F-FDG-PET/CT scanning is helpful in ascertaining the correct diagnosis in more than 50% of the cases presenting with FUO and IUO. Absence of intermittent fever, higher age and elevated CRP level increase the likelihood for a diagnostic ¹⁸F-FDG-PET/CT.

Different Scoring Methods of FDG PET/CT in Giant Cell Arteritis: Need for Standardization

Giant cell arteritis (GCA) is the most frequent form of vasculitis in persons older than 50 years. Cranial and systemic large vessels can be involved. [¹⁸F] fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is increasingly used to diagnose inflammation of the large arteries in GCA. Unfortunately, no consensus exists on the preferred scoring method. In the present study, we aim to define the optimal FDG PET/CT scoring method for GCA diagnosis using temporal artery biopsy and clinical diagnosis as the reference method. FDG PET/CT scans of GCA patients (12 glucocorticoid-naive, 6 on glucocorticoid treatment) and 3 control groups (inflammatory, atherosclerotic, and normal controls) were evaluated. We compared 2 qualitative visual methods (i.e. (1a) first impression and (1b) vascular uptake versus liver uptake) and 4 semiquantitative methods ((2a) SUVmax aorta, (2b) SUVmax aorta-to-liver ratio, (2c) SUVmax aorta-to-superior-caval-vein ratio, and (2d) SUVmax aorta-to-inferior-caval-vein ratio). FDG uptake pattern (diffuse or focal) and presence of arterial calcifications were also scored. Diagnostic accuracy of the visual method vascular versus liver uptake (1b) was highest when the cut-off point "vascular uptake higher than liver uptake" (sensitivity 83%, specificity 91%) was used. Sensitivity increased to 92% when patients on glucocorticoids were excluded from the analysis. Regarding the semiquantitative methods, the aorta-to-liver ratio (2b) with a cutoff of 1.03 had the highest diagnostic accuracy, with a sensitivity and specificity of 69% and 92%, respectively. Sensitivity increased to 90% when patients on glucocorticoids were excluded. The number of vascular segments with diffuse FDG uptake pattern was significantly higher in GCA patients without glucocorticoid use compared with all control patient groups. CRP was not significantly different between positive and negative FDG PET scans in the GCA group. Visual vascular uptake higher than liver uptake resulted in the highest diagnostic accuracy for the detection of GCA, especially in combination with a diffuse FDG uptake pattern. Of the semiquantitative methods, the aorta-to-liver SUVmax ratio (cutoff point = 1.03) had the highest diagnostic accuracy. The diagnostic accuracy increased when patients using glucocorticoids were excluded from the analyses.

¹⁸F-FDG PET/CT in inflammation of unknown origin: a cost-effectiveness pilot-study

PURPOSE

Patients with increased inflammatory parameters, nonspecific signs and symptoms without fever and without a diagnosis after a variety of diagnostic procedures are a diagnostic dilemma and are referred to as having inflammation of unknown origin (IUO). The objective of this pilot study was to compare the cost-effectiveness of a diagnostic work-up/strategy with and without (18)F-FDG PET/CT in patients with IUO using a published dataset as a reference.

METHODS

IUO patients without (18)F-FDG PET/CT (group A, 46 patients) and IUO patients referred for (18)F-FDG PET/CT (group B, 46 patients) were selected. IUO was defined as the combination of nonspecific signs and symptoms and a prolonged erythrocyte sedimentation rate (ESR), defined as ≥age/2 in men and ≥(age + 10)/2 in women (ESR in millimetres per hour and age in years), and/or C-reactive protein (CRP) ≥15 mg/l. The costs of all tests and procedures and the number of hospitalization days in each patient to reach a diagnosis were calculated using current Dutch tariffs.

RESULTS

In group A a diagnosis was reached in 14 of the 46 patients. The mean cost per patient of all the diagnostic procedures was <euro>2,051, and including the cost of hospitalization was <euro>12,614. In group B a diagnosis was reached in 32 of the 46 patients. The mean cost per patient of all the diagnostic procedures was <euro>1,821, significantly lower than in group A (p < 0.0002), and including the cost of hospitalization was <euro>5,298.

CONCLUSION

In IUO (18)F-FDG PET/CT has the potential to become a cost-effective routine imaging technique indicating the direction for further diagnostic decisions thereby allowing unnecessary, invasive and expensive diagnostic investigations to be avoided and possibly the duration of hospitalization to be reduced. However, a prospective multicentre "bottom-up microcosting" cost-effectiveness study is warranted before these preliminary data can be extrapolated to clinical practice.

Large-vessel vasculitis: interobserver agreement and diagnostic accuracy of 18F-FDG-PET/CT

Introduction. ¹⁸F-FDG-PET visualises inflammation. Both atherosclerosis and giant cell arteritis cause vascular inflammation, but distinguishing the two may be difficult. The goal of this study was to assess interobserver agreement and diagnostic accuracy of ¹⁸F-FDG-PET for the detection of large artery involvement in giant cell arteritis (GCA). Methods. 31 ¹⁸F-FDG-PET/CT scans were selected from 2 databases. Four observers assessed vascular wall ¹⁸F-FDG uptake, initially without and subsequently with predefined observer criteria (i.e., vascular wall ¹⁸F-FDG uptake compared to liver or femoral artery ¹⁸F-FDG uptake). External validation was performed by two additional observers. Sensitivity and specificity of ¹⁸F-FDG-PET were determined by comparing scan results to a consensus diagnosis. Results. The highest interobserver agreement (kappa: 0.96 in initial study and 0.79 in external validation) was observed when vascular wall ¹⁸F-FDG uptake higher than liver uptake was used as a diagnostic criterion, although agreement was also good without predefined criteria (kappa: 0.68 and 0.85). Sensitivity and specificity were comparable for these methods. The criterion of vascular wall ¹⁸F-FDG uptake equal to liver ¹⁸F-FDG uptake had low specificity. Conclusion. Standardization of image assessment for vascular wall ¹⁸F-FDG uptake promotes observer agreement, enables comparative studies, and does not appear to result in loss of diagnostic accuracy compared to nonstandardized assessment.

The role of 18F-FDG PET/CT in large-vessel vasculitis: appropriateness of current classification criteria?

Patients with clinical suspicion of large-vessel vasculitis (LVV) may present with nonspecific signs and symptoms and increased inflammatory parameters and may remain without diagnosis after routine diagnostic procedures. Both the nonspecificity of the radiopharmaceutical ¹⁸F-FDG and the synergy of integrating functional and anatomical images with PET/CT offer substantial benefit in the diagnostic work-up of patients with clinical suspicion for LVV. A negative temporal artery biopsy, an ultrasonography without an arterial halo, or a MRI without aortic wall thickening or oedema do not exclude the presence of LVV and should therefore not exclude the use of ¹⁸F-FDG PET/CT when LVV is clinically suspected. This overview further discusses the notion that there is substantial underdiagnosis of LVV. Late diagnosis of LVV may lead to surgery or angioplasty in occlusive forms and is often accompanied by serious aortic complications and a fatal outcome. In contrast to the American College of Rheumatology 1990 criteria for vasculitis, based on late LVV effects like arterial stenosis and/or occlusion, ¹⁸F-FDG PET/CT sheds new light on the classification of giant cell arteritis (GCA) and Takayasu arteritis (TA). The combination of these observations makes the role of ¹⁸F-FDG PET/CT in the assessment of patients suspected for having LVV promising.

FDG PET imaging in cystic fibrosis

Cystic fibrosis (CF) is characterized by persistent neutrophilic lung inflammation that begins early in life and leads to an inexorable progressive loss of lung function over time, causing significant morbidity and mortality. Studies to date support the hypothesis that higher levels of lung inflammation lead to worsening lung dysfunction. However, measuring the extent and severity of lung inflammation in the CF lung is difficult as few lung-specific biomarkers of inflammation can quantify the regional and whole-lung inflammatory burden accurately and reproducibly. PET with (18)F-fluorodeoxyglucose ((18)F-FDG) has shown promise in measuring lung inflammation in both acute and chronic lung diseases. Several studies have now shown that (18)F-FDG uptake may be a useful measure of lung inflammation in CF. The whole-lung rate of (18)F-FDG uptake in stable CF, quantified by the Patlak graphical analysis, appears to correlate with more rapidly declining lung function. Acute exacerbation, on the contrary, leads to focally increased (18)F-FDG uptake, which decreases with antibiotic treatment. These small studies are the first attempts to characterize the patterns of (18)F-FDG uptake in CF and suggest a potential role for (18)F-FDG as a treatment modifiable biomarker of lung inflammation in CF.

Large vessel vasculitis in elderly patients: early diagnosis and steroid-response evaluation with FDG-PET/CT and contrast-enhanced CT

Large vessel vasculitis (LVV) is an often-reported cause of inflammation of unknown origin (IUO) in elderly people. The objective of this study was to describe the usefulness of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) and contrast-enhanced CT in early diagnosis and treatment follow-up of patients with LVV presenting as elderly onset IUO. We retrospectively compared contrast-enhanced CT findings and FDG-PET/CT findings of the patients diagnosed with LVV and 11 controls; all subjects were 50 years of age or older. We evaluated maximum standardised uptake value (SUV(max)) and PET score of the aortic wall for quantitative comparison of FDG-PET/CT findings. We measured the aortic wall thickness (W) and its ratio against the radius (W/R) for quantitative comparison of aortic wall thickening by contrast-enhanced CT. After steroid treatment, we compared these values with those pre-treatment. Of 124 patients who were hospitalised due to advanced age and IUO, 88 underwent FDG-PET/CT and contrast-enhanced CT. Abnormal findings were observed on images from 78 patients. The findings were indicative of LVV in 13 patients (10.5 %), of whom more than half had only non-specific symptoms. Patients with LVV had significantly higher aortic wall SUV(max) (3.85 vs. 1.95), PET scores by FDG-PET/CT, and aortic wall thicknesses by contrast-enhanced CT (3.8 vs. 2.6 mm) than controls. Significant improvement in aortic wall thickening was evidenced by reduced PET scores and by contrast-enhanced CT findings in patients who were followed up after treatment. LVV is an important cause of IUO with non-specific symptoms in elderly patients. Imaging examination comprising contrast-enhanced CT and FDG-PET/CT is useful for early diagnosis and early treatment evaluation of LVV, allowing for amelioration of reversible aortic wall thickening.