Current situation and cost-effectiveness of 18F-FDG PET/CT for the diagnosis of fever of unknown origin and inflammation of unknown origin: a single-center, large-sample study from China

The diagnostic role of 2-[18F]FDG PET/CT in critically ill patients with suspected infection of unknown origin: a real-world experience

PURPOSE

2-Deoxy-2-[18F]-fluoro-D-glucose (2-[18F]FDG) positron emission tomography/computed tomography (PET/CT) is a hybrid imaging tool with an emerging role in the study of several infectious and inflammatory diseases. Its role in critically ill patients admitted to the intensive care unit (ICU) is only marginally investigated. This study aimed to investigate the diagnostic performance and the clinical impact of 2-[18F]FDG PET/CT in the management of critically ill patients with suspected infections of unknown origin.

METHODS

We retrospectively included 47 ICU patients (mean age 63.6 years, 33 males) who underwent a 2-[18F]FDG PET/CT to look for infection foci. We calculated the diagnostic performance of PET/CT expressed as sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy. As reference standard, final diagnosis based on microbiological/pathologic data or on clinical follow-up was taken. Moreover, we investigated the impact of PET/CT on clinical management and the association of PET/CT with the main clinical, epidemiological and biochemical parameters.

RESULTS

The overall 2-[18F]FDG PET/CT sensitivity in detecting infectious foci was 80% (95%CI 64-91%), specificity 75% (95%CI 35-97%), PPV 94% (95%CI 83-93%), NPV 43% (95%CI 26-61%) and accuracy 79% (95%CI 65-90%). The absence of kidney failure, increase leukocyte count and low glucose level at the time of PET were significantly associated with true positive PET/CT. No adverse events during the transport and PET/CT procedure were registered.

CONCLUSION

PET/CT demonstrated to be an accurate toll for the study of critically ill ICU patients with suspected infections. Kidney failure, leukocyte count and blood glucose were associated with true positive PET/CT.

Role of FDG PET/CT in bacteremia and fever of unknown origin: a pictorial overview of finding the culprit

18F fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) has established itself as a critical diagnostic tool in the evaluation of patients with bacteremia and fever of unknown origin (FUO), particularly following futile conventional investigations. These conditions are often challenging due to diverse underlying etiologies, including infections, inflammatory conditions and malignancies. PET/CT has the advantage of being a whole-body imaging technique with high sensitivity for detecting areas of increased metabolism often associated with infection or inflammation. In bacteremia, [18F]FDG PET/CT can help identify metastatic infections, endocarditis, or abscesses which may be clinically silent and missed on conventional imaging. In FUO, it helps to identify underlying etiologies, directing treatment and management strategies. This review aims to describe the role of PET/CT imaging in these diverse clinical scenarios. Perspectives in the field, including novel equipment and tracers, will be briefly discussed.

Diagnostic efficacy and necessity of 18F-FDG PET/CT in fever of unknown origin: insights from a retrospective cohort study

Background

Despite advancements in medical examination equipment and techniques, fever of unknown origin (FUO) remains challenging in internal medicine.

Purpose

This study evaluates the diagnostic efficacy and necessity of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with FUO.

Methods

We retrospectively analyzed the results of 18F-FDG PET/CT in a cohort of 284 patients with FUO admitted to the Department of Infection at the First Hospital of Jilin University between January 2018 and March 2024. All patients received a final clinical diagnosis after various treatments, which helped determine the diagnostic relevance of identified lesions using 18F-FDG PET/CT. Additionally, univariate and multivariate logistic regression analyses were performed to evaluate the predictive value of relevant laboratory indices on the true-positive results of 18F-FDG PET/CT. The diagnostic performance for different etiologies of FUO was assessed by calculating the area under the receiver operating characteristic curve.

Results

Of the 284 enrolled patients, infectious diseases were diagnosed in 53 (18.7%), non-infectious inflammatory diseases in 76 (26.8%), malignant tumors in 66 (23.2%), and 89 (31.3%) remained undiagnosed. The final diagnoses of 136 patients (47.9%) correlated with their 18F-FDG PET/CT results, yielding a sensitivity of 79.5%, specificity of 61.1%, positive predictive value of 75.6%, and negative predictive value of 66.3%. Furthermore, a correlation was found between localized pain, prolonged activated partial thromboplastin time, and true-positive 18F-FDG PET/CT results.

Conclusion

The high diagnostic efficacy of 18F-FDG PET/CT in FUO suggests its potential as a routine imaging modality, which could enhance patient management and reduce the need for costly and unnecessary invasive procedures. The identification of clinical factors that are predictive of true-positive diagnosis could facilitate more effective allocation of PET/CT imaging.

Role of 18 F-FDG PET/CT for providing a targeted approach for etiology of PUO

AIM

This study aimed to evaluate the potential role of 18F-fluorodeoxyglucose PET/computed tomography (18F-FDG PET/CT) in providing a targeted approach for diagnosing the etiology of Pyrexia of Unknown Origin (PUO).

METHODS

A total of 573 PUO patients were included in this ambispective study, with a mean age of 39.40 ± 4.6 years. Patients underwent FDG PET/CT scans using dedicated hybrid scanners. PET/CT data were interpreted by experienced nuclear medicine physicians. The study analyzed the guidance provided by FDG PET/CT for appropriate biopsy sites and assessed concordance between PET/CT findings and histopathological examination.

RESULTS

Out of the 573 patients, a final diagnosis was reached for 219 patients, including malignancy, infectious causes, noninfectious inflammatory causes (NIID), and precancerous conditions. FDG PET/CT played a crucial role in guiding clinicians to appropriate biopsy sites, contributing to a higher diagnostic yield. Concordance between PET/CT findings and histopathological examination emphasized the noninvasive diagnostic potential of PET/CT in identifying underlying causes of PUO. Overall, FDG PET/CT contributed to guiding the appropriate site of biopsy or concordance of the first differential diagnosis with the final diagnosis in 50.05% of cases.

CONCLUSION

This study highlights the valuable role of FDG PET/CT in providing a targeted approach for diagnosing PUO, showcasing its potential in guiding clinicians towards appropriate biopsy sites and improving the diagnostic yield. The findings underscore the importance of integrating FDG PET/CT into the diagnostic pathway for PUO, ultimately enhancing patient management and outcomes. Further prospective studies are necessary to validate these results and refine the integration of FDG PET/CT in the diagnosis of PUO.

Performance of [18F]FDG PET/CT in Diagnosing Cyst Infections in Patients with Autosomal Dominant Polycystic Kidney Disease: A Systematic Review and a Bivariate Meta-Analysis

BACKGROUND

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) has been suggested as a useful imaging method for diagnosing cyst infections in patients with autosomal dominant polycystic kidney disease (ADPKD). The aim of this article is to provide evidence-based data in this setting.

METHODS

A systematic literature review (exploring several bibliographic databases) and a bivariate meta-analysis were carried out to calculate the pooled diagnostic performance of [18F]FDG PET/CT in diagnosing probable cyst infection in ADPKD.

RESULTS

Ten studies (282 PET/CT scans and 249 patients) were included in the analysis. The pooled sensitivity and specificity of [18F]FDG PET/CT in this setting were 84.6% (95% confidence interval: 75.4-90.7) and 94.9% (95% confidence interval: 72.6-99.2), respectively, without statistical heterogeneity or significant publication bias. [18F]FDG PET/CT significantly changed patient management in more than half of ADPKD patients with suspected cyst infection.

CONCLUSIONS

[18F]FDG PET/CT has high performance in diagnosing probable cyst infections in ADPKD patients with an impact on management in the majority of patients. Although more studies are warranted, the provided evidence-based data are an important step towards the integration of [18F]FDG PET/CT in clinical and diagnostic guidelines on probable cyst infection in ADPKD patients.

EANM consensus document on the use of [18F]FDG PET/CT in fever and inflammation of unknown origin

PURPOSE

Patients with fever and inflammation of unknown origin (FUO/IUO) are clinically challenging due to variable clinical presentations with nonspecific symptoms and many differential diagnoses. Positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is increasingly used in FUO and IUO, but the optimal diagnostic strategy remains controversial. This consensus document aims to assist clinicians and nuclear medicine specialists in the appropriate use of [18F]FDG-PET/CT in FUO and IUO based on current evidence.

METHODS

A working group created by the EANM infection and inflammation committee performed a systematic literature search based on PICOs with "patients with FUO/IUO" as population, "[18F]FDG-PET/CT" as intervention, and several outcomes including pre-scan characteristics, scan protocol, diagnostic yield, impact on management, prognosis, and cost-effectiveness.

RESULTS

We included 68 articles published from 2001 to 2023: 9 systematic reviews, 49 original papers on general adult populations, and 10 original papers on specific populations. All papers were analysed and included in the evidence-based recommendations.

CONCLUSION

FUO and IUO remains a clinical challenge and [18F]FDG PET/CT has a definite role in the diagnostic pathway with an overall diagnostic yield or helpfulness in 50-60% of patients. A positive scan is often contributory by directly guiding treatment or subsequent diagnostic procedure. However, a negative scan may be equally important by excluding focal disease and predicting a favorable prognosis. Similar results are obtained in specific populations such as ICU-patients, children and HIV-patients.

Comparison of diagnostic spectrum between inflammation of unknown origin and fever of unknown origin: A systematic review and meta-analysis

BACKGROUND

Patients with inflammation of unknown origin (IUO) and fever of unknown origin (FUO) are commonly considered a single population. Differences in underlying causes between both groups may steer the diagnostic work-up.

METHODS

PubMed, Embase, Web of Science, and ClinicalTrials.gov were searched from July 2009 through December 2023. Studies including both FUO and IUO patients with a sample size of ≥20 were considered. The primary outcome was the difference in the rate of patients affected by predefined diagnostic categories according to meeting FUO or IUO criteria. Data were pooled using random-effects models.

RESULTS

A total of 8 studies met criteria for inclusion, with a total of 1452 patients (466 with IUO and 986 with FUO). The median rate of IUO patients among the included studies was 32 % (range 25-39 %). Patients with IUO had a lower likelihood of infection (OR 0.59 [95 % CI; 0.36-0.95]; I2 0 %). There were no significant differences in the rate of noninfectious inflammatory disorders, malignancies, miscellaneous disorders, or remaining undiagnosed. Comparison of diagnostic subgroups revealed that IUO patients were less likely to have systemic autoinflammatory disorders (OR 0.17 [95 % CI, 0.05-0.58]; I2 42 %) and more likely to have vasculitis (OR 2.04 [95 % CI, 1.23-3.38]; I2 21 %) and rheumatoid arthritis or spondylarthritis (OR 3.52 [95 % CI, 1.16-10.69]; I2 0 %).

CONCLUSION

Based on our findings, there is little reason to assume that FUO and IUO patients would benefit from a different initial diagnostic approach.

Nuclear Medicine Imaging Tools in Fever of Unknown Origin: Time for a Revisit and Appropriate Use Criteria

Fever of unknown origin (FUO) is a clinical conundrum for patients and clinicians alike, and imaging studies are often performed as part of the diagnostic workup of these patients. Recently, the Society of Nuclear Medicine and Molecular Imaging convened and approved a guideline on the use of nuclear medicine tools for FUO. The guidelines support the use of 2-18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) in adults and children with FUO. 18F-FDG PET/CT allows detection and localization of foci of hypermetabolic lesions with high sensitivity because of the 18F-FDG uptake in glycolytically active cells that may represent inflammation, infection, or neoplasia. Clinicians should consider and insurers should cover 18F-FDG PET/CT when evaluating patients with FUO, particularly when other clinical clues and preliminary studies are unrevealing.

[Inflammatory syndrome of unknown origin and PET/CT: Economic and iatrogenic impacts of false positive]

INTRODUCTION

PET/CT is regularly used to investigate inflammatory syndrome of unknown origin (IUO), but hypermetabolisms found are not always consistent with the final diagnosis. The objective of the study was to assess the cost attributed to the diagnostic work-up for these false positives.

MATERIALS AND METHODS

We conducted an ancillary study on a previous retrospective cohort from the internal medicine department at Amiens university hospital in patients who had a PET/CT scan between October 2004 and April 2017. Patients were included if PET/CT had been prescribed to investigate IUO. Among the 763 PET/CT performed, 144 met the inclusion criteria and a false-positive rate of 17.4% (n=25) was reported.

RESULTS

Among these 25 patients, 21 underwent further investigations. The most frequently found hypermetabolic territories were digestive (n=12, mean SUVmax 8 [±4.33]) and osteoarticular (n=11, mean SUVmax 4.33 [±1.15]). The total cost of the 13 prescribed consultations was €390, the total cost of the 40 additional tests was €4,476 (mainly digestive endoscopies and radiological tests) and the total cost of medical transport was €572. The total cost of the 35 days of hospitalization specifically required to investigate these false positives was €22,952. In 23.8% (n=5), these investigations led to the incidental discovery of tumor lesions.

CONCLUSION

The economic impact of false-positive PET/CT results does not appear to be negligible and merits a genuine prospective medico-economic study.

FDG-PET/CT for investigation of pyrexia of unknown origin: a cost of illness analysis

BACKGROUND

Our study aims to explore the current utilisation of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the diagnostic pathway of pyrexia of unknown origin (PUO) and associated cost of illness in a large tertiary teaching hospital in Australia.

METHOD

1257 febrile patients between June 2016 and September 2022 were retrospectively reviewed. There were 57 patients who met the inclusion criteria of "classical PUO", of which FDG-PET/CT was performed in 31 inpatients, 15 outpatients and 11 inpatients did not have an FDG-PET/CT scan. The patient demographics, clinical characteristics and inpatient cost were analysed, together with the diagnostic performance of FDG-PET/CT and impact on clinical management.

RESULT

The mean age, length of stay and total cost of admission were higher for inpatients who received FDG-PET/CT versus those who did not. The median cost per patient-bed-day did not differ between the two groups. Inpatients who received earlier FDG-PET/CTs (≤ 7 days from admission) had shorter length of stays and lower total cost compared to those who received a later scan. A negative FDG-PET/CT scan, demonstrating no serious or life-threatening abnormalities resulted in subsequent discharge from hospital or outpatient clinic in 7/10 (70%) patients. There were 11/40 (28%) scans where ancillary abnormalities were identified, requiring further evaluation.

CONCLUSION

FDG-PET/CT showed high diagnostic accuracy and significant impact on patient management in patients with PUO. FDG-PET/CT performed earlier in admission for PUO was associated with shorter length of stay and lower total cost.

Update on imaging in fever and inflammation of unknown origin: focus on infectious disorders

BACKGROUND

Fever of unknown origin (FUO) and inflammation of unknown origin (IUO) are diagnostic challenges that often require an extensive work-up. When first-line tests do not provide any or only misleading clues, second-line investigations such as specialized imaging techniques are often warranted.

OBJECTIVES

To provide an overview of the diagnostic value of imaging techniques that are commonly used in patients with FUO/IUO.

SOURCES

MEDLINE database was searched to identify the most relevant studies, trials, reviews, or meta-analyses until 31 March 2023.

CONTENT

The most important types of second-line imaging tests for FUO and IUO are outlined, including [67Ga]-citrate single-photon emission computed tomography/computed tomography (CT), labelled leukocyte imaging, [18F]-fluorodeoxyglucose positron emission tomography CT ([18F]-FDG-PET), and whole-body magnetic resonance imaging. This review summarizes the diagnostic yield, extends on potential future imaging techniques (pathogen-specific bacterial imaging and [18F]-FDG-PET/magnetic resonance imaging), discusses cost-effectiveness, highlights practical implications and pitfalls, and addresses future perspectives. Where applicable, we provide additional data specifically for the infection subgroup.

IMPLICATIONS

Although many imaging examinations are proven to be useful in FUO and IUO, [18F]-FDG-PET/CT is the preferred second-line test when available as it provides a high diagnostic yield in a presumably cost-effective way.

Development of a Consensus-Based List of Potential Quality Indicators for Fever and Inflammation of Unknown Origin

With a growing emphasis on value-based reimbursement, developing quality indicators for infectious diseases has gained attention. Quality indicators for fever of unknown origin and inflammation of unknown origin are lacking. An assembled group of international experts developed 12 quality measures for these conditions, which could be validated with additional study.

FDG PET in Evaluation of Patients With Fever of Unknown Origin: AJR Expert Panel Narrative Review

Fever of unknown origin (FUO) is a diagnostic challenge, with its cause remaining undiagnosed in approximately half of patients. Nuclear medicine tests typically are performed after a negative or inconclusive initial workup. Gallium-67 citrate and labeled leukocytes were previous mainstays of radionuclide imaging for FUO, although they had limited diagnostic performance. FDG PET/CT has subsequently emerged as the nuclear medicine imaging test of choice, supported by a growing volume of evidence. A positive FDG PET/CT result contributes useful information by identifying potential causes of fever, localizing sites for further evaluation, and guiding further management; a negative result contributes useful information by excluding focal disease as the cause of fever and predicts a favorable prognosis. In 2021, CMS rescinded a prior national noncoverage determination for FDG PET for infection and inflammation, leading to increasing national utilization of FDG PET/CT for FUO workup. This article reviews the current status of the role of FDG PET/CT in the evaluation of patients with FUO. The literature reporting the diagnostic performance and yield of FDG PET/CT in FUO workup is summarized, with comparison with historically used nuclear medicine tests included. Attention is also given to the test's clinical impact; protocol, cost, and radiation considerations; and application in children.

Optimal use of the FDG-PET/CT in the diagnostic process of fever of unknown origin (FUO): a comprehensive review

Numerous studies have clarified the usefulness of ¹⁸F-fluorodeoxyglucose (FDG)-PET/CT (positron emission tomography) for diagnosing the cause of fever of unknown origin (FUO). Various types of disease can cause FUO, but the cause remains unknown in a certain proportion of FUO, even when the advanced diagnostic methodologies are used. FDG-PET/CT is regarded as a second-line modality in the diagnostic process of FUO, and its potential to identify the cause of FUO will be maximized when the appropriate clinical considerations are understood. Accordingly, this review presents basic knowledge regarding FUO, and reports the current status of FDG-PET/CT applied to diagnosing the cause of FUO, including diagnostic performance, test protocols, possible factors influencing the diagnostic result, outcomes, and cost-effectiveness. This knowledge will enable effective future use of FDG-PET/CT to improve outcomes in patients with FUO.

The Diagnostic Value of Fluoro-18 Fluorodeoxyglucose (F-18 FDG) PET/CT in Fever or Inflammation of Unknown Origin: A Retrospective Study at a Rheumatology Clinic

Introduction Further diagnostic procedures are necessary for patients with fever of unknown origin (FUO) and unknown cause of inflammation (inflammation of unknown origin - IUO) for the identification of the definitive diagnosis. The aim of this study was to evaluate the contribution and roles of F-18 FDG PET/CT (fluoro-18 fluorodeoxyglucose-positron emission tomography/computed tomography) in the diagnostic process of patients with FUO/IUO. Methods The data of 58 patients who had F-18 FDG PET/CT scans for FUO/IUO were re-evaluated retrospectively. The relationships between definitive diagnosis and fluorodeoxyglucose uptake and SUVmax (maximum standardized uptake value) were examined. Results  Rheumatic disease was diagnosed in 26 patients (44.5%), malignancy in 20 patients (34.5%), and infectious diseases in six patients (10.3%). The most prevalent rheumatic disease in patients with FUO/IUO was systemic vasculitis (n:10, 17.2%), especially large vessel vasculitis. There were 37 patients (63.7%) with clinically significant true positive fluorodeoxyglucose uptake. True positive fluorodeoxyglucose uptake was significantly higher in patients diagnosed with malignancy (85%, 17/20 patients) compared to other diagnoses. Fluorodeoxyglucose uptake above physiological levels was determined in 15 of the 26 patients (57.6%) diagnosed with rheumatic diseases. Conclusion The results of this study showed that F-18 FDG PET/CT is a useful imaging modality in FUO/IUO patients, who present a challenging diagnostic process for clinicians. In addition to malignancies, the presence of chronic inflammatory diseases, especially early period systemic vasculitis, were diagnosed in these patients.