A prospective multi-centre study of the value of FDG-PET as part of a structured diagnostic protocol in patients with fever of unknown origin

Clinical characteristics of lymphoma patients presenting with fever of unknown origin misdiagnosed with connective tissue diseases

Recognizing and diagnosing lymphoma in patients with fever of unknown origin (FUO) can be challenging, and misdiagnosis is not uncommon. To improve understanding of the clinical characteristics of lymphoma patients presenting with FUO who were misdiagnosed with autoimmune diseases. A retrospective, observational study of 140 consecutive patients with FUO and lymphoma presenting to a tertiary center between January 2017 and December 2023. Patients were divided into those who were correctly diagnosed and those misdiagnosed as connective tissue diseases (CTD) and the clinical features compared. Of 140 lymphoma patients with FUO, 21 patients (15.0%) were misdiagnosed as CTD. The median time between symptom onset and diagnosis was significantly longer in the misdiagnosed group than in the non-misdiagnosed group (11.0 (IQR 6.0, 22.5) months vs. 4.0 (2.5, 9.0) months; p = 0.001). The misdiagnosed group had significantly less lymph node and bone marrow involvement and more skin rashes than the non-misdiagnosed group (47.6% vs. 70.6%, p = 0.039; 23.8% vs. 47.9%, p = 0.040; 47.6% vs. 25.2%, p = 0.036), as well as significantly lower ESR (p = 0.026) and hsCRP (p = 0.049). The misdiagnosed group had higher frequency of ANA/ANCA (57.1% vs. 27.7%; p = 0.008) and anti-phospholipid antibody (42.9% vs. 6.1%; p = 0.008) positivity. The distribution of lymphoma subtypes was different between groups (p = 0.058). Lymphoma patients with an atypical presentation and FUO suggesting inflammatory systemic disease are easily misdiagnosed. Autoantibody positivity is not rare in lymphoma patients with an atypical presentation and FUO, so close follow-up and repeated histopathological examination may be helpful to establishing a correct diagnosis.

Metagenomic next-generation sequencing in patients with fever of unknown origin: A comprehensive systematic literature review and meta-analysis

Metagenomic Next-Generation Sequencing (mNGS) holds promise in diagnosing fever of unknown origin (FUO) by detecting diverse pathogens. We systematically reviewed the literature to evaluate mNGS's accuracy, clinical efficacy, and limitations in FUO diagnosis. Nine studies revealed mNGS's positivity rate ranging from 66.7% to 93.5% for bacterial bloodstream infections and systemic infections. Meta-analysis of three studies involving 857 patients, including 354 with FUO, showed a sensitivity of 0.91 (95% CI: 0.87-0.93) and specificity of 0.64 (95% CI: 0.58-0.70). Despite lower specificity, mNGS demonstrated a higher Diagnostic Odds Ratio (DOR) of 17.0 (95% CI: 4.5-63.4) compared to conventional microbiological tests (CMTs) at 4.7 (95% CI: 2.9-7.6). While mNGS offers high sensitivity but low specificity in identifying causative pathogens for FUO, its superior DOR suggests potential for more accurate diagnoses and targeted interventions. Further research is warranted to optimize its clinical application in FUO management.

The Contribution of 18F FDG PET-CT for the Investigation of Fever of Unknown Origin and Inflammation of Unknown Origin

BACKGROUND

Fever of unknown origin and inflammation of unknown origin are highly challenging diagnostic conditions. The current practice for evaluating patients is to conduct a positron emission tomography-computed tomography (PET-CT) scan as either a first- or a second-line modality. We aimed to assess the contributory effect of PET-CT to the diagnosis and compare it with the contributory effect of CT alone.

METHODS

We performed a systematic review and meta-analysis. We included all cohorts that examined the contribution of PET-CT to the investigation of classical fever of unknown origin and inflammation of unknown origin. The primary outcome was the contribution of PET-CT to the final diagnosis. Secondary outcomes were sensitivity and specificity of PET-CT and CT scans, and contribution of a CT scan. We pooled the results of all studies and calculated the pooled contributory effect of PET-CT.

RESULT

Thirty-six studies (3516 patients) were included in the systematic review. The pooled contribution of PET-CT was 75.4%. The compiled sensitivity and specificity values for all studies were 85.9% and 59.5%, respectively. Five studies (405 patients) compared between the PET-CT component and the total body CT component. The pooled contribution of a CT scan was 68%. The summed sensitivity and specificity values of a CT scan for all studies were 63.1% and 84.4%, respectively.

CONCLUSIONS

PET-CT has a contributory effect of 75% for the diagnosis of fever of unknown origin and inflammation of unknown origin. PET-CT had superior sensitivity and inferior specificity vs the CT scan.

Recurrent (or episodic) fever of unknown origin (FUO) as a variant subgroup of classical FUO: A French multicentre retrospective study of 170 patients

BACKGROUND

Recurrent FUO (fever of unknown origin) is a rare subtype of FUO for which diagnostic procedures are ill-defined and outcome data are lacking.

METHODS

We performed a retrospective multicentre study of patients with recurrent FUO between 1995 and 2018. By multivariate analysis, we identified epidemiological, clinical and prognostic variables independently associated with final diagnosis and mortality.

RESULTS

Of 170 patients, 74 (44%) had a final diagnosis. Being ≥ 65 years of age (OR = 5.2; p < 0.001), contributory history (OR = 10.4; p < 0.001), and abnormal clinical examination (OR = 4.0; p = 0.015) independently increased the likelihood of reaching a diagnosis, whereas lymph node and/or spleen enlargement decreased it (OR = 0.2; p = 0.004). The overall prognosis was good; 58% of patients recovered (70% of those with a diagnosis). Twelve (7%) patients died; patients without a diagnosis had a fatality rate of 2%. Being ≥ 65 years of age (OR = 41.3; p < 0.001) and presence of skin signs (OR = 9.5; p = 0.005) significantly increased the risk of death.

CONCLUSION

This study extends the known yield of recurrent FUO and highlights the importance of repeated complete clinical examinations to discover potential diagnostic clues during follow-up. Moreover, their overall prognosis is excellent.

Pulmonary and Urologic Sarcoidosis as a Cause of Intermittent Fever of Unknown Origin

Diagnosing fever of unknown origin (FUO) presents a substantial challenge due to its potential association with various diseases affecting different organs. In 1961, Petersdorf and Beeson initially defined FUO as a condition characterized by a temperature exceeding 38.3 °C on at least three occasions over a minimum three-week period. Despite a week of inpatient investigation, a definitive diagnosis remains unclear.  Sarcoidosis, a granulomatous disease impacting multiple systems, is among the causes of FUO. While the lungs are commonly affected, any organ can be involved, leading to diverse manifestations and clinical courses. Diagnosis relies on clinicopathologic findings and the exclusion of alternative causes of granulomatous disease. The hallmark of sarcoidosis is the development of granulomas in affected organs. Here, we present the case of a 61-year-old man with a history of recurrent spontaneous periurethral abscesses who underwent multiple urological interventions. He developed FUO during hospitalization following treatment for the infectious condition.

B-Cell Lymphoma With Prominent Presentation of Lactic Acidosis: A Case Report and Brief Review of the Literature

Lactic acidosis is a rare but severe complication of B-cell lymphoma, often associated with rapid disease progression and poor prognosis. We present a case of a 60-year-old male admitted with fever, splenomegaly, hemophagocytic tendencies, and lactic acidosis. The patient underwent several dialysis sessions before bone marrow flow cytometry finally confirmed B-cell lymphoma. However, hyperlactatemia persisted and recurred. The case underscores the challenges in diagnosing lymphomas with atypical presentations and emphasizes the critical role of timely bone marrow analysis. Additionally, the paper discusses the association between B-cell lymphoma and lactic acidosis, highlighting the importance of early recognition and intervention.

Differential diagnosis of lymphoma with 18F-FDG PET/CT in patients with fever of unknown origin accompanied by lymphadenopathy

PURPOSE

To investigate the value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the differential diagnosis of lymphoma in patients with fever of unknown origin (FUO) accompanied by lymphadenopathy and to develop a simple scoring system to distinguish lymphoma from other etiologies.

METHODS

A prospective study was conducted on patients with classic FUO accompanied by lymphadenopathy. After standard diagnostic procedures, including PET/CT scan and lymph-node biopsy, 163 patients were enrolled and divided into lymphoma and benign groups according to the etiology. The diagnostic utility of PET/CT imaging was evaluated, and beneficial parameters that could improve diagnostic effectiveness were identified.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PET/CT in diagnosing lymphoma in patients with FUO accompanied by lymphadenopathy were 81.0, 47.6, 59.3, and 72.7%, respectively. The lymphoma prediction model combining high SUVmax of the "hottest" lesion, high SUVmax of the retroperitoneal lymph nodes, old age, low platelet count, and low ESR had an area under the curve of 0.93 (0.89-0.97), a sensitivity of 84.8%, a specificity of 92.9%, a PPV of 91.8%, and an NPV of 86.7%. There was a lower probability of lymphoma for patients with a score < 4 points.

CONCLUSIONS

PET/CT scans show moderate sensitivity and low specificity in diagnosing lymphoma in patients with FUO accompanied by lymphadenopathy. The scoring system based on PET/CT and clinical parameters performs well in differentiating lymphoma and benign causes and can be used as a reliable noninvasive tool.

REGISTRATION NUMBER

This study on FUO was registered on http://www.

CLINICALTRIALS

gov on January 14, 2014, with registration number NCT02035670.

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.

Predictors for spontaneous resolution of classical FUO in patients undergoing PET-CT

Spontaneous resolution is common in patients with classic fever of unknown origin (FUO). Identifying predictors of spontaneous resolution could reduce the usage of unnecessary, invasive tests or empirical therapy, and furthermore reduce patient anxiety. Identify predictors associated with spontaneous resolution of FUO. A single center, retrospective, cohort study. All hospitalized patients who underwent an ^[18F] FDG PET-CT scan for the investigation of classical FUO between 1/2012 and 1/2020 were included. We compared patients with spontaneous resolution of fever and clinical symptoms, to those who were diagnosed with a specific etiology of FUO (subdivided to infectious diseases, non-infectious inflammatory diseases (NIID), and malignancies). Epidemiologic characteristics as well as laboratory and PETCT study results were compared. Variables that were found to be associated with spontaneous resolution of FUO on univariate analysis (p < 0.1) were entered into a multivariable regression analysis. The results are reported as odds ratios (OR) and 95% confidence intervals (CI). A total of 303 patients were hospitalized for the investigation of classical FUO and underwent complete assessment. Fever resolved without a diagnosis in 84/303 patients (28%). Variables that were associated with spontaneous resolution of FUO on multivariable analysis included: no anemia, no hypoalbuminemia and no pathological FDG uptake on PET-CT. In 17.8% (15/84) of studies, PET-CT yielded false-positive results that led to additional unnecessary, invasive investigation. Patients without anemia or hypoalbuminemia, and those without uptake on PET-CT are more likely to have spontaneous resolution of classical FUO.

Diagnostic models for fever of unknown origin based on 18F-FDG PET/CT: a prospective study in China

Background

This study aims to analyze the 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) characteristics of different causes of fever of unknown origin (FUO) and identify independent predictors to develop a suitable diagnostic model for distinguishing between these causes. A total of 524 patients with classical FUO who underwent standard diagnostic procedures and PET/CT were prospectively studied. The diagnostic performance of PET/CT imaging was analyzed, and relevant clinical parameters that could improve diagnostic efficacy were identified. The model was established using the data of 369 patients and the other 155 patients comprised the validation cohort for verifying the diagnostic performance of the model.

Results

The metabolic characteristics of the “hottest” lesion, the spleen, bone marrow, and lymph nodes varied for various causes. PET/CT combined with clinical parameters achieved better discrimination in the differential diagnosis of FUO. The etiological diagnostic models included the following factors: multisite metabolic characteristics, blood cell counts, inflammatory indicators (erythrocyte sedimentation rate, C-reactive protein, serum ferritin, and lactate dehydrogenase), immunological indicators (interferon gamma release assay, antinuclear antibody, and anti-neutrophil cytoplasm antibody), specific signs (weight loss, rash, and splenomegaly), and age. In the testing cohort, the AUCs of the infection prediction model, the malignancy diagnostic model, and the noninfectious inflammatory disease prediction model were 0.89 (95% CI 0.86–0.92), 0.94 (95% CI 0.92–0.97), and 0.95 (95% CI 0.93–0.97), respectively. The corresponding AUCs for the validation cohort were 0.88 (95% CI 0.82–0.93), 0.93 (95% CI 0.89–0.98), and 0.95 (95% CI 0.92–0.99), respectively.

Conclusions

18F-FDG PET/CT has a certain level of sensitivity and accuracy in diagnosing FUO, which can be further improved by combining it with clinical parameters. Diagnostic models based on PET/CT show excellent performance and can be used as reliable tools to discriminate the cause of FUO.

Trial registration This study (a two-step method apparently improved the physicians’ level of diagnosis decision-making for adult patients with FUO) was registered on the website http://www.clinical-trials.gov on January 14, 2014, with registration number NCT02035670.

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.

Fever of unknown origin (FUO) in children: a single-centre experience from Beijing, China

OBJECTIVE

To date, there is no standard diagnostic practice to identify the underlying disease-causing mechanism for paediatric patients suffering from chronic fever without any specific diagnosis, which is one of the leading causes of death in paediatric patients. Therefore, we aimed this retrospective study to analyse medical records of paediatric patients with fever of unknown origin (FUO) to provide a preliminary basis for improving the diagnostic categories and facilitate the treatment outcomes.

DESIGN

A retrospective study.

SETTING

Beijing Children's Hospital.

PARTICIPANTS

Clinical data were collected from 1288 children between 1 month and 18 years of age diagnosed with FUO at Beijing Children's Hospital between January 2010 and December 2017.

INTERVENTIONS

According to the aetiological composition, age, duration of fever and laboratory examination results, the diagnostic strategies were analysed and formulated.

PRIMARY AND SECONDARY OUTCOME MEASURES

The statistical analyses were carried out using SPSS V.24.0 platform along with the χ² test and analysis of variance (p<0.05).

RESULTS

The duration of fever ranged from 2 weeks to 2 years, with an average of 6 weeks. There were 656 cases (50.9%) of infectious diseases, 63 cases (4.9%) of non-infectious inflammatory diseases (NIIDs), 86 cases (6.7%) of neoplastic diseases, 343 cases (26.6%) caused by miscellaneous diseases and 140 cases (10.9%) were undiagnosed. With increasing age, the proportion of FUO from infectious diseases gradually decreased from 73.53% to 44.21%. NIID was more common in children over 3 years old, and neoplastic diseases mainly occurred from 1 to 6 years of age. Among miscellaneous diseases, the age distribution was mainly in school-aged children over 6 years. Respiratory tract infection was the most common cause of FUO in children, followed by bloodstream infections. Bacterial infection was the most common cause in children with less than 1 year old, while the virus was the main pathogen in children over 1 year old.

CONCLUSIONS

The diagnosis of neoplastic diseases and miscellaneous diseases-related diseases still depends mainly on invasive examination. According to our clinical experience, the diagnostic process was formulated based on fever duration and the type of disease. This process can provide a guide for the diagnosis and treatment of paediatric FUO in the future.

Diagnostic Value of 18F-FDG PET/CT vs. Chest-Abdomen-Pelvis CT Scan in Management of Patients with Fever of Unknown Origin, Inflammation of Unknown Origin or Episodic Fever of Unknown Origin: A Comparative Multicentre Prospective Study

Fluorodesoxyglucose Positron Emission Tomography (PET/CT) has never been compared to Chest-Abdomen-Pelvis CT (CAPCT) in patients with a fever of unknown origin (FUO), inflammation of unknown origin (IUO) and episodic fever of unknown origin (EFUO) through a prospective and multicentre study. In this study, we investigated the diagnostic value of PET/CT compared to CAPCT in these patients. The trial was performed between 1 May 2008 through 28 February 2013 with 7 French University Hospital centres. Patients who fulfilled the FUO, IUO or EFUO criteria were included. Diagnostic orientation (DO), diagnostic contribution (DC) and time for diagnosis of both imaging resources were evaluated. One hundred and three patients were included with 35 FUO, 35 IUO and 33 EFUO patients. PET/CT showed both a higher DO (28.2% vs. 7.8%, p < 0.001) and DC (19.4% vs. 5.8%, p < 0.001) than CAPCT and reduced the time for diagnosis in patients (3.8 vs. 17.6 months, p = 0.02). Arthralgia (OR 4.90, p = 0.0012), DO of PET/CT (OR 4.09, p = 0.016), CRP > 30 mg/L (OR 3.70, p = 0.033), and chills (OR 3.06, p = 0.0248) were associated with the achievement of a diagnosis (Se: 89.1%, Sp: 56.8%). PET/CT both orients and contributes to diagnoses at a higher rate than CAPCT, especially in patients with FUO and IUO, and reduces the time for diagnosis.

The yield of F18 FDG PET-CT for the investigation of fever of unknown origin, compared with diagnostic CT

BACKGROUND

18F-Fluoro-2-deoxy-D-glucose (FDG) positron emission tomography, with contrast enhanced CT (PET-CT), is recommended as a first or a second-line imaging method for the evaluation of patients with fever of unknown origin (FUO). We evaluated the yield of PET-CT vs. contrast enhanced CT (alone) for the diagnosis of classical FUO.

METHODS

A single center, 8-year retrospective cohort study. All hospitalized patients who underwent PET-CT for the investigation of classical FUO between 1/2012-1/2020 were included. The final diagnosis, based on clinical, microbiological, radiological and pathological data available at the latest follow-up, at least six months after discharge, was determined. For each case, we determined whether the diagnosis would have been reached based on the CT scan alone, or based on the PET-CT (thus, defining PET-CT as necessary). We compared the overall sensitivity and specificity results for both PET-CT and CT scan. Variables that were found to be significantly associated with PET-CT necessity on univariable analysis were entered into a multivariable logistic regression analysis. The results of the regression model were reported in odds ratios (OR) and 95% confidence intervals (CI).

RESULT

A total of 303 patients with classical FUO were referred for PET-CT. The final diagnoses included infectious diseases in 111/303 patients (36.5%), malignancies in 56/303 patients (18.4%) and non-infectious inflammatory conditions in 52/303 patients (17.1%). FUO resolved without diagnosis in 84/303 patients (28%). The overall sensitivity and specificity of the PET-CT scans were 88.7% and 80.9%, respectively, and for the CT scans were 75.2% and 90.2%, respectively. PET-CT had superior sensitivity vs CT (p=0.00) for all subgroups, with generally decreased specificity than CT for infections and inflammatory conditions. PET-CT was determined as necessary in 26% (79/303) of the patients. Endovascular infection, hematological malignancy and large vessel vasculitis were the only factors associated with PET-CT necessity on multivariable analysis.

CONCLUSIONS

PET-CT offers superior sensitivity with slightly decreased specificity for the diagnosis of classical FUO compared to diagnostic CT. We recommend PET-CT as the imaging modality of choice for patients with classical FUO, when endovascular infection, hematological malignancy or large vessel vasculitis are suspected.

Disseminated Coccidioidomycosis Presenting as Fever of Unknown Origin and Erythema Nodosum in a 3-Year-Old Child

Disseminated coccidioidomycosis is a disease caused by Coccidioides species, fungi endemic to the southwestern United States. We present here an uncommon case of a young child with erythema nodosum and fever of unknown origin, found to have the infection. While more common in adults, coccidioidomycosis should be considered in all patients with erythema nodosum.

PET/MRI in paediatric disease

Nuclear medicine and molecular imaging have a small but growing role in the management of paediatric and neonatal diseases. During the past decade, combined PET/MRI has emerged as a clinically important hybrid imaging modality in paediatric medicine due to diagnostic advantages and reduced radiation exposure compared to alternative techniques. The applications for nuclear medicine, radiopharmaceuticals and combined PET/MRI in paediatric diagnosis is broadly similar to adults, however there are some key differences. There are a variety of clinical applications for PET/MRI imaging in children including, but not limited to, oncology, neurology, cardiovascular, infection and chronic inflammatory diseases, and in renal-urological disorders. In this article, we review the applications of PET/MRI in paediatric and neonatal imaging, its current role, advantages and disadvantages over other hybrid imaging techniques such as PET/CT, and its future applications. Overall, PET/MRI is a powerful imaging technology in diagnostic medicine and paediatric diseases. Higher soft tissue contrasts and lower radiation dose of the MRI makes it the superior technology compared to other conventional techniques such as PET/CT or scintigraphy. However, this relatively new hybrid imaging has also some limitations. MRI based attenuation correction remains a challenge and although methodologies have improved significantly in the last decades, most remain under development.

Place of the 18F-FDG-PET/CT in the Diagnostic Workup in Patients with Classical Fever of Unknown Origin (FUO)

Objective: To explore the diagnostic contribution of the ¹⁸F-FDG-PET/CT in a population of patients with classical fever of unknown origin (FUO), to pinpoint its place in the diagnostic decision tree in a real-life setting, and to identify the factors associated with a diagnostic ¹⁸F-FDG-PET/CT. Method: All adult patients (aged ≥ 18 years) with a diagnosis of classical FUO who underwent an ¹⁸F-FDG-PET/CT in the University Hospital of Montpellier (France) between April 2012 and December 2017 were included. True positive ¹⁸F-FDG-PET/CT, which evidenced a specific disease causing FUO, were considered to be contributive. Results: Forty-four patients with FUO have been included (20 males, 24 females; mean age 57.5 ± 17.1 years). Diagnoses were obtained in 31 patients (70.5%), of whom 17 (38.6%) had non-infectious inflammatory diseases, 9 had infections (20.5%), and 3 had malignancies (6.8%). ¹⁸F-FDG-PET/CT was helpful for making a final diagnosis (true positive) in 43.6% of all patients. Sensitivity and specificity levels were 85% and 37%, respectively. A total of 135 investigations were performed before ¹⁸F-FDG-PET/CT, mostly CT scans (93.2%) and echocardiography (59.1%), and 108 after ¹⁸F-FDG-PET/CT, mostly biopsies (including the biopsy of a temporal artery) (25%) and MRIs (34%). In multivariate analysis, the hemoglobin level was significantly associated with a helpful ¹⁸F-FDG-PET/CT (p = 0.019, OR 0.41; 95% CI (0.20–0.87)), while the CRP level was not associated with a contributive ¹⁸F-FDG-PET/CT. Conclusion: ¹⁸F-FDG-PET/CT may be proposed as a routine initial non-invasive procedure in the diagnostic workup of FUO, especially in anemic patients who could be more likely to benefit from ¹⁸F-FDG-PET/CT.

The diagnostic value of 18F-FDG PET/CT in identifying the causes of fever of unknown origin

BACKGROUND

This study investigated the clinical significance of ¹⁸F-fluorodeoxyglucose positron emission tomography / computed tomography (¹⁸F-FDG PET/CT) in identifying the causes of fever of unknown origin (FUO).

METHODS

Patients with a fever who received an ¹⁸F-FDG PET/CT examination were retrospectively selected. The means of the two groups were compared using an independent-samples t-test.

RESULTS

Among the 89 included patients, 66 were diagnosed using ¹⁸F-FDG PET/CT. The sensitivity, specificity and diagnostic accuracy of ¹⁸F-FDG PET/CT for the diagnosis of patients with FUO were 84.5%, 25.8%, and 64.0%, respectively. The detection rates of ¹⁸F-FDG PET/CT for neoplastic diseases, infectious diseases and non-infectious inflammatory diseases were 100%, 61.3%, and 75%, respectively. The difference in C-reactive protein (CRP) levels between the two groups was statistically significant.

CONCLUSIONS

¹⁸F-FDG PET/CT has great clinical importance in diagnosing and identifying causes of FUO and improves the accuracy of FUO diagnosis when combined with serum CRP levels.

Diagnostic Splenectomy: Characteristics, Pre-Operative Investigations, and Identified Pathologies for 20 Patients

Splenectomy is indicated in cases of trauma to the spleen or hematological and immunological diseases (hereditary spherocytosis, autoimmune cytopenia). Less frequently, splenectomy is performed for diagnostic purposes to complement unsuccessful prior etiological investigations. The splenectomy remains a surgery at risk of complications and should be considered as a last-resort procedure to make the diagnosis and to be able to treat patients. We studied the medical files of 142 patients who underwent a splenectomy for any reason over a 10-year period and identified 20 diagnostic splenectomies. Diagnostic splenectomies were mainly performed to explore unexplained splenomegaly for 13 patients and fever of unknown origin for 10. The other patients had surgery for other causes (cytopenia, abdominal symptoms, suspicion of relapsing malignant hemopathies). Splenectomy contributed to the final diagnosis in 19 of 20 cases, corresponding mostly to lymphoid hemopathies (14/20). The most frequent disease was diffuse large B-cell lymphoma (8/20). Splenectomy did not reveal any infectious disease. The most relevant pre-operative procedures to aid the diagnosis were ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) and immuno-hematological examinations. Diagnostic splenectomy is useful and necessary in certain difficult diagnostic situations. Highlights: Diagnostic splenectomy is still useful in 2020 to diagnose unexplained splenomegaly or fever of unknown origin. Lymphoma was the most common final diagnosis. FDG PET/CT was the most useful tool to aid in the diagnosis.

Multidisciplinary Management of a Frequent Attender With Pyrexia of Unknown Origin and Psychotic Symptoms

This case report details the multidisciplinary management of a frequent attender in his early 50s with no fixed abode who presented with pyrexia of unknown origin, complicated by his noncooperation with intervention and treatment because of the development of psychotic symptoms. The case required the involvement of liaison psychiatry, anesthesia, cardiology, radiology, gastroenterology, rheumatology, respiratory, hematology, and social services, highlighting not just multidisciplinary intervention but the benefits of working with a multispeciality team. The patient had previously presented to the emergency department 47 times over an 18-month period. The management during his most recent inpatient stay resulted in the patient living independently and presenting to the hospital only once over the ensuing 7 months.

FDG-PET/CT in Fever of Unknown Origin, Bacteremia, and Febrile Neutropenia

Fever of unknown origin, bacteremia, and febrile neutropenia are diagnostic challenges. FDG-PET/CT is a well-established modality in infection imaging and the literature increasingly supports its use in these settings. In fever of unknown origin, FDG-PET/CT is helpful, but diagnostic yield depends on patient selection and inflammatory markers. In bacteremia, FDG-PET/CT is cost-effective, reduces morbidity and mortality, and impacts treatment strategy. Although use of FDG-PET/CT in these domains is not established as part of a definitive diagnostic strategy, FDG-PET/CT may help establish final diagnosis in a difficult population and should be considered early in the diagnostic process.

Diagnostic Value of 18F-FDG-PET/CT in Patients with FUO

Conventional diagnostic imaging is often ineffective in revealing the underlying cause in a considerable proportion of patients with fever of unknown origin (FUO). The aim of this study was to assess the diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) in patients with FUO. We retrospectively reviewed ¹⁸F-FDG-PET/CT scans performed on 50 consecutive adult patients referred to our department for further investigation of classic FUO. Final diagnosis was based on histopathological and microbiological findings, clinical criteria, or clinical follow-up. Final diagnosis was established in 39/50 (78%) of the patients. The cause of FUO was infection in 20/50 (40%), noninfectious inflammatory diseases in 11/50 (22%), and malignancy in 8/50 (16%) patients. Fever remained unexplained in 11/50 (22%) patients. ¹⁸F-FDG-PET/CT scan substantially contributed to the diagnosis in 70% of the patients, either by identifying the underlying cause of FUO or by directing to the most appropriate site for biopsy. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of ¹⁸F-FDG-PET/CT for active disease detection in patients with FUO were 94.7%, 50.0%, 84.0%, 85.7%, and 75.0%, respectively. In conclusion, whole-body ¹⁸F-FDG-PET/CT is a highly sensitive method for detection of the underlining cause of FUO or for correctly targeting suspicious lesions for further evaluation.

Classic fever of unknown origin: analysis of a cohort of 87 patients according to the definition with qualitative study criterion

OBJECTIVES

The aim of this study was to evaluate the characteristics of fever of unknown origin (FUO) according to the definition with qualitative study criterion and of patients without diagnosis.

MATERIALS AND METHODS

Prospective observational study performed from 2009 to 2017 of all patients who were diagnosed with FUO according to the extended definition with qualitative study criterion. Demographic, clinical, diagnostic and evolving variables were evaluated.

RESULTS

Of the 87 patients registered, 17.3% presented criteria of inflammation of unknown origin (IUO). The diagnoses were: non-infectious inflammatory diseases (NIID) in 19 patients (21.8%), infections in 15 (17.2%), miscellaneous in 14 (16.1%), malignant diseases in 13 (15%) and without diagnosis in 26 (29.9%). In 17.6% of the cases, a potentially diagnostic clue (PDC) was identified. The patients without diagnosis were characterized by a lower number of total PDC (5.9±3.3 vs. 8.7±3.4; P=.000), fewer clinical signs (.4±.6 vs. .9±.8; P=.001), a smaller number of tests in the previous study (2.7±2.1 vs. 4.6±2; P=.000), a shorter diagnostic interval (14.6±7.7 days vs. 21.4±9.5 days; P=.029) and less alteration of erythrocyte sedimentation rate (52.3±41.3mm/h vs. 89.8±42.7mm/h; P=.000), haemoglobin (12.9±1.7g/dl vs. 11.7±1.6g/dl; P=.003) and albumin (36.9±6.4g/l vs. 33.2±7.2g/l; P=.025). ¹⁸F-fluorodeoxyglucose positron-emission tomography combined with computed tomography (¹⁸F-FDG-PET/TC) proved to be helpful in 37% of the cases. Mortality was 6.8%.

CONCLUSIONS

The definition of FUO with qualitative study criterion incorporates a diagnostic protocol that provides clear benefits in terms of cost-effectiveness.

Diagnostic accuracy of 18F-FDG-PET in abdominal sepsis in rats

Purpose

The objective of this study was to investigate the accuracy of 18F-FDG-PET in the diagnosis of multibacterial abdominal sepsis by cecum ligation and puncture (CLP) in rats.

Methods

Adult Wistar rats ( Rattus norvegicus ), weighing 227±35g, were allocated into a sepsis group by CLP (n=10) and sham group (n=10). 18F-FDG-PET using microPET was performed on all rats after 24 hours.

Results

All animals survived for postoperative 24h. The abdomen/liver ratio of the standardized uptake value (SUV) percentage was significantly higher in the sepsis group than in the sham (p=0.004). The ROC curve showed an accuracy of 18F-FDG-PET to detect abdominal sepsis of 88.9% (p=0.001), sensitivity of 90% and specificity of 88.9%. When a cut-off point of 79% of the ratio between the SUV on the abdominal region and liver was established, the sensitivity was 90%, specificity of 88.9%; positive and negative predictive values of 90.0% and 88.9%, respectively.

Conclusions

The diagnostic accuracy of 18F-FDG-PET in rats with abdominal sepsis was significantly high. It was also demonstrated the predictive ability of the abdomen/liver SUV ratio to diagnose abdominal sepsis. These findings may have implications for the clinical setting, locating septic foci with PETscan.

Retrospective analysis of 1,641 cases of classic fever of unknown origin

Background

Fever of unknown origin (FUO) is commonly defined as fever higher than 38.3 °C on several occasions during at least 3 weeks with uncertain diagnosis after a number of obligatory investigations. It is a special type of fever and a common disease in internal medicine. However, due to its complex etiology, lack of characteristic clinical manifestations, and insufficient laboratory examination indicators, it often baffles clinicians in diagnosis. We herein present a study of the etiological factors and clinical features of classic fever of unknown origin (FUO) to provide help for related clinical diagnosis and treatment.

Methods

A total of 1,641 cases of patients with classic FUO hospitalized in West China Hospital of Sichuan University between January 1, 2011 and December 31, 2017, were collected, and the etiological factors of classic FUO were analyzed. A special effort was made to explore and screen the laboratory indicators related to infectious diseases, and the above data were compared with the clinical features of tuberculosis and lymphoma, which are difficult to diagnose.

Results

Among the 1,641 patients, 1,504 were finally diagnosed through various types of examination or diagnostic methods, and the diagnosis rate was 91.65%. Among all the causes of the 1,641 cases of FUO, 48.69% [799] were infectious diseases, of which tuberculosis was the most common, accounting for 19.50% [320]. Connective tissue diseases were responsible for 19.26% [316] of cases, of which adult-onset Still's disease (AOSD) was the most common, comprising 89 (5.42%) of the cases; 16.94% [278] were neoplastic diseases, and lymphoma (143, 8.71%) cases, was the most common malignant tumor; 6.76% [111] were other diseases; and in 8.35% [137] of cases, the cause was unclear. Through comparative analysis of tuberculosis and lymphoma, no significant differences were found between the symptoms, signs, and non-specific routine examination results of the two diseases. The diagnosis of these diseases was more dependent on tuberculosis-related examinations and pathological examinations.

Conclusions

Infectious diseases are the principal cause of classic FUO, in which tuberculosis accounts for a large proportion. Non-infectious diseases that cause FUO are mainly connective tissue diseases and malignant tumors. Of the various causes of classic FUO, tuberculosis and lymphoma are relatively difficult to diagnose. In most cases, the causes of classic FUO can be ascertained.

Bilateral End-Organ Endophthalmitis in Setting of Serratia marcescens Urosepsis on 18F-FDG PET/CT

Endogenous endophthalmitis is an uncommon infection of the internal tissues of the eye resulting from a bloodborne infection. We present the case of an 89-year-old man with Serratia marcescens urosepsis with multifocal end-organ infection on F-FDG PET/CT including aortitis, splenic abscess, septic arthritis, thoracolumbar discitis-osteomyelitis, and culture-confirmed bilateral endogenous endophthalmitis. Endophthalmitis-related intraconal ocular space uptake was clearly distinguishable from normal conal space extraocular muscle activity. Although sepsis responded to treatment, endophthalmitis led to complete vision loss. This case report presents PET/CT description of a rare and difficult-to-treat Serratia marcescens endogenous endophthalmitis, which usually has a poor visual outcome.

Fever of unknown origin: a retrospective review of pediatric patients from an urban, tertiary care center in Washington, DC

BACKGROUND

Fever of unknown origin (FUO) continues to challenge clinicians to determine an etiology and the need for treatment. This study explored the most common etiologies, characteristics, and average cost of hospitalization for FUO in a pediatric population at an urban, tertiary care hospital in Washington, DC.

METHODS

Records from patients admitted to Children's National Health System between September 2008 and April 2014 with an admission ICD-9 code for fever (780.6) were reviewed. The charts of patients 2-18 years of age with no underlying diagnosis and a temperature greater than 38.3 ºC for 7 days or more at time of hospitalization were included. Final diagnoses, features of admission, and total hospital charges were abstracted.

RESULTS

110 patients qualified for this study. The majority of patients (n = 42, 38.2%) were discharged without a diagnosis. This was followed closely by infection, accounting for 37.2% (n = 41) of patients. Rheumatologic disease was next (n = 16, 14.5%), followed by miscellaneous (n = 6, 5.4%) and oncologic diagnoses (n = 5, 4.5%). The average cost of hospitalization was 40,295 US dollars.

CONCLUSIONS

This study aligns with some of the most recent publications which report undiagnosed cases as the most common outcome in patients hospitalized with FUO. Understanding that, often no diagnosis is found may reassure patients, families, and clinicians. The cost associated with hospitalization for FUO may cause clinicians to reconsider inpatient admission for diagnostic work-up of fever, particularly given the evidence demonstrating that many patients are discharged without a diagnosis.

Combined clinical parameters improve the diagnostic efficacy of 18F-FDG PET/CT in patients with fever of unknown origin (FUO) and inflammation of unknown origin (IUO): A prospective study in China

OBJECTIVES

To improve the diagnostic efficacy of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for Chinese patients with fever of unknown origin (FUO) and inflammation of unknown origin (IUO), with combined clinical parameters.

MATERIALS AND METHODS

FUO/IUO patients who underwent a standard diagnostic work-up and ¹⁸F-FDG PET/CT scanning were enrolled and divided into a local uptake lesion subgroup and a non-specific abnormal uptake subgroup. Beneficial clinical parameters for improving the diagnostic efficacy of PET/CT were identified.

RESULTS

From January 2014 to January 2019, 253 FUO/IUO patients were studied. In total, 147 patients had local uptake lesions and 106 patients had non-specific abnormal uptake. In the local uptake lesion group, the positioning accuracy of PET/CT was 37.2% in grades 1 and 2, and 66.3% in grades 3 and 4. With the following combination of clinical parameters, the positioning accuracy increased to 75.0% and 90.0%, respectively: time from admission to performing PET/CT scanning <6.5 days and C-reactive protein level >95 mg/l. In the non-specific abnormal uptake group, the combination of sex (male), bicytopenia, and lactic dehydrogenase improved the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for diagnosing malignancy from 64.3%, 69%, 60%, and 72.7%, respectively, to 83.3%, 81%, 81.4%, and 82.9%, respectively. With the combination of sex (male), white blood count, serum ferritin level, and hepatosplenomegaly, the infection prediction model had a sensitivity, specificity, PPV, and NPV of 78%, 76.2%, 76.6%, and 77.6%, respectively.

CONCLUSIONS

Combined clinical parameters improved the localization diagnostic value of ¹⁸F-FDG PET/CT in the local uptake lesion subgroup and the etiological diagnostic value in the non-specific abnormal uptake subgroup.

Prolonged Fever, Diarrhea, Abdominal Pain, and Joint Pain in a 9-Year- Old Boy

A 9-year-old African American boy was admitted to hospital with a 12-day history of fevers, diarrhea, abdominal pain and a 1-day history of joint pain. His abdominal pain and diarrhea resolved within the first few days of admission, but he continued with high-grade fevers and intermittent joint pain. The joints affected included the right first interphalangeal joint, right wrist, right elbow, and left knee joint. His initial laboratory tests revealed normal complete blood count, comprehensive metabolic panel, and C-reactive protein. Consequently, he developed fatigue, lower back pain, and bicytopenias. After 19 days of fevers, a multispecialty collaborative evaluation arrived at a final diagnosis and treatment plan. In this article, we discuss the child's hospital course and our clinical thought process. Written consent was obtained from the family.

Fever of unknown origin - a literature review

Fever of undetermined origin (FUO) is a challenging entity with a striking presence in hospitals around the world and can be associated with a myriad of differential diagnoses. It is defined as axillary temperature ≥ 37.8 ° C on several occasions, lasting ≥ three weeks, in the absence of diagnosis after three days of hospital investigation or three outpatient visits. The main etiologies are: infectious, neoplastic, and rheumatic. The diagnosis is based on the detailed clinical history and physical examination of these patients, in order to direct the specific complementary tests to be performed in each case. Empirical therapy is not recommended (with few exceptions) in patients with prolonged fever, as it may disguise and delay the diagnosis and conduct to treat the specific etiology. The prognosis encompasses mortality of 12% - 35%, varying according to the underlying etiology. In this sense, the objective of this study is to review the main topics about fever of undetermined origin, bringing historical and scientific aspects, national and international.

PET/CT Imaging in Soft Tissue Infection and Inflammation-An Update

Nuclear medicine procedures, including Ga-67 and labeled leucocyte SPECT/CT as well as PET/CT using 18F-FDG and recently Ga-68 tracers, have found extensive applications in the assessment of infectious and inflammatory processes in general and in soft tissues in particular. Recent published data focus on summarizing the available imaging information with the purpose of providing the referring clinicians with optimized evidence based results. Guidelines and/or recommendations of clinical societies have incorporated nuclear medicine tests (using both labeled leucocytes and FDG) in their suggested work-up for evaluation of infective endocarditis and in certain patients with suspected vascular graft infections. Joint guidelines of the European and American nuclear medicine societies include fever of unknown origin, sarcoidosis, and vasculitis among the major clinical indications that will benefit from nuclear medicine procedures, specifically from FDG PET/CT. Limitations and pitfalls for the use of radiotracers in assessment of infection and inflammation can be related to patient conditions (eg, diabetes mellitus), or to the biodistribution of a specific radiopharmaceutical. Limited presently available data on the use of functional and/or metabolic monitoring of response to infectious and inflammatory processes to treatment and with respect to the effect of drugs such as antibiotics and glucocorticoids on the imaging patterns of these patients need further confirmation.

Optimal use of [18F]FDG-PET/CT in patients with fever or inflammation of unknown origin

BACKGROUND

[¹⁸F]FDG-PET/CT is one of the most important diagnostic techniques in the work-up of patients with fever of unknown origin (FUO)/inflammation of unknown origin (IUO). Little is known on how to optimize the diagnostic value of [¹⁸F]FDG-PET/CT in patients with FUO/IUO.

METHODS

Retrospective study in all patients who underwent [¹⁸F]FDG-PET/CT during the work-up of FUO/IUO in a tertiary expert center between 2005 and 2014. Data were extracted from medical records.

RESULTS

One hundred and four patients were identified, of whom 68 had a final diagnosis (65.4%). Mainly infections (30.8%) and non-infectious inflammatory diseases (30.8%). [¹⁸F]FDG-PET/CT contributed to the final diagnosis in 47 of the 68 patients (69.1%). In 21 patients [¹⁸F]FDG-PET/CT did not help making a diagnosis. In ten of these patients [¹⁸F]FDG-PET/CT was performed while body temperature, CRP and ESR were normal or unknown. Sixteen of 104 patients underwent repeated [¹⁸F]FDG-PET/CT. The second scan contributed to the final diagnosis in five of these patients. In two of these patients, the first scan retrospectively was truly non-contributory. In both patients the first [¹⁸F]FDG-PET/CT was made while CRP/ESR was low and fever was not present or not measured. A third or fourth scan never contributed to the final diagnosis when the second one did not.

CONCLUSIONS

[¹⁸F]FDG-PET/CT contributed to the final diagnosis in 45.2% of patients, but never contributed when both inflammatory parameters and body temperature were normal. Repeating [¹⁸F]FDG-PET/CT should only be done in patients with a non-contributory [¹⁸F]FDG-PET/CT when new symptoms or signs appear, or when the first scan was made in absence of fever or elevated inflammatory parameters.

Contribution of 18F-FDG PET/CT in a case-mix of fever of unknown origin and inflammation of unknown origin: a meta-analysis

BACKGROUND

Fever of unknown origin (FUO) and inflammation of unknown origin (IUO) are challenging medical problems. Previous studies have shown that 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) plays an important role in the diagnosis of FUO, but few studies have explored this diagnostic technique in relation to IUO.

PURPOSE

To systematically review and perform a meta-analysis of published data on the diagnostic performance of PET/CT in the diagnosis of FUO and IUO.

MATERIAL AND METHODS

A comprehensive literature search was performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines published in March 2018. Meta-analysis of diagnostic performance was performed using STATA 12.0 software. Subgroup analysis was performed by stratification based on study design, number of patients, geographic area, and final diagnosis based on 18F-FDG PET/CT. Meta-regression analyses were performed to recognize heterogeneity.

RESULTS

Our meta-analysis included 23 studies, comprising a total sample size of 1927 patients. The pooled diagnosis performance was calculated with a per-patient-based analysis: sensitivity = 0.84 (95% confidence interval [CI] = 0.79-0.89), specificity = 0.63 (95% CI = 0.49-0.75), positive likelihood ratio = 2.3 (95% CI = 1.5-3.4), negative likelihood ratio = 0.25 (95% CI = 0.16-0.38), diagnostic odds ratio = 9 (95% CI = 4.0-20), and AUC = 0.84 (95% CI = 0.81-0.87).

CONCLUSION

In patients with non-specific symptoms and signs, 18F-FDG PET/CT is very helpful for recognizing and excluding diseases, directing further diagnostic decisions, and avoiding unnecessary invasive examinations. We recommend that 18F-FDG PET/CT should be considered among the first-line diagnostic tools for patients with FUO and IUO.

Delayed diagnosis of extrapulmonary tuberculosis presenting as fever of unknown origin in an intermediate-burden country

Background

Tuberculosis (TB), especially extrapulmonary tuberculosis (EPTB), is an important cause of fever of unknown origin (FUO) in TB-burdened areas. Little information is known about patients with EPTB with clinical features presenting as FUO and about the factor of delaying the diagnosis.

Methods

We retrospectively analyzed EPTB patients who were referred with FUO at 3 university-affiliated hospitals over 8 years (2010–2017). The subjects were assigned to groups of early diagnosis and delayed diagnosis within 3 days of an initial comprehensive evaluation from the referral. Clinical and laboratory variables were compared between the groups.

Results

A total of 95 patients with febrile EPTB were included. Localizing symptoms and/or signs suggestive of anatomy were identified in 62.1% of the patients. Concurrent lung involvement by TB was presented by 49.5% (47/95) of the patients, and only 23.4% of them showed typical findings of pulmonary TB on simple chest X-ray. Most of the patients showed abnormal lesions on cross-sectional CT (98.9%) and MRI (100%). The clinical variables and blood test results of patients were not significantly different between the two groups. The less typical imaging finding of EPTB on CT (38.5% vs. 79.0%) and MRI (37.5% vs. 79.0%) in the delayed diagnosis group was a risk factor for delayed diagnosis.

Conclusion

Febrile EPTB referred as FUO showed nonspecific clinical manifestations. The active application of cross-sectional imaging tests according to clinical clues or randomly in the absence of local manifestations, combined with invasive diagnostic approaches even for atypical presentations may lead to an earlier diagnosis of febrile EPTB.

18F-FDGPET/CT in fever of unknown origin and inflammation of unknown origin: a Chinese multi-center study

PURPOSE

To evaluate the clinical value of ¹⁸F-FDG-PET/CT for the diagnosis of fever of unknown origin (FUO) and inflammation of unknown origin (IUO) in Chinese population, as well as the characteristics of PET/CT in different category of etiological disease.

METHODS

A total of 376 consecutive patients with FUO/IUO who underwent FDG-PET/CT at 12 hospitals were retrospectively studied. FDG uptake was quantitatively and visually evaluated, by using SUV_max and a 4-grade scale respectively. A questionnaire survey to the clinicians was used to evaluate the significance of PET/CT in diagnosing of FUO/IUO. Data analysis included the etiological distribution in the study population, image characteristics in different category of diseases, and clinical significance of PET/CT.

RESULTS

In 376 studied patients, the infectious diseases accounted for 33.0% of patients, rheumatologic diseases for 32.4%, malignancies for 19.1%, miscellaneous causes for 6.6%, and cause unknown for 8.8%. However, the etiological distribution among hospitals was varied. In addition, the etiological disease composition ratio has changed over time in China. On PET/CT examinations, 358 (95.2%) of the patients had a positive finding. Within them, local high uptake lesion was found in 219 cases, and nonspecific abnormal uptake (NAU) was found in 187 cases. FDG uptake in malignant diseases was significantly higher than in other category diseases both on SUV_max and visual scores (t-value range from 4.098 to 5.612, all P value < 0.001). Based on a clinical questionnaire survey, PET/CT provided additional diagnostic information for 77.4% of patients, and 89.6% of patients benefited from PET/CT examination.

CONCLUSIONS

FDG PET/CT is a valuable tool for clinical diagnosis of FUO/IUO, and it is of great significance in further investigating the usefulness of PET/CT in non-neoplastic diseases.

Clinical analysis of 215 consecutive cases with fever of unknown origin: A cohort study

Fever of unknown origin (FUO) is a frequently observed phenomenon in clinical practice. The present study was aimed to investigate potential causes of FUO, thereby improving clinical diagnosis of this disorder.In this retrospective study, clinical data were collected from 215 patients who were diagnosed with FUO between January 2009 and December 2010, and an 18 to 36 months follow-up visit was also performed for these patients.Among these FUO cases, the most common causes of the disease were infectious diseases (IDs) (42.3%), followed by connective tissue diseases (CTDs) (32.1%), miscellaneous (Mi) (10.7%) and neoplasm (N) (6.5%), while the causes for the other 18 cases (8.4%) were still unknown. The most common types of ID, CTD, and N were tuberculosis (16/91, 17.6%), adult onset Still disease (AOSD) (37/69, 53.6%) and non-Hodgkin lymphoma (6/14, 42.9%), respectively.IDs still represent the most common causes of FUO. Regularly intermittent fever with urinary infections and irregularly intermittent fever with infective endocarditis may be regarded as some signs in clinical diagnosis of FUO.

Pyrexia of unknown origin

The syndrome of pyrexia of unknown origin (PUO) was first defined in 1961 but remains a clinical challenge for many physicians. Different subgroups with PUO have been suggested, each requiring different investigative strategies: classical, nosocomial, neutropenic and HIV-related. This could be expanded to include the elderly as a fifth group. The causes are broadly divided into four groups: infective, inflammatory, neoplastic and miscellaneous. Increasing early use of positron emission tomography-computed tomography (PET-CT) and the development of new molecular and serological tests for infection have improved diagnostic capability, but up to 50% of patients still have no cause found despite adequate investigations. Reassuringly, the cohort of undiagnosed patients has a good prognosis. In this article we review the possible aetiologies of PUO and present a systematic clinical approach to investigation and management of patients, recommending potential second-line investigations when the aetiology is unclear.

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.

Fever of Unknown Origin: the Value of FDG-PET/CT

Fever of unknown origin (FUO) is commonly defined as fever higher than 38.3°C on several occasions during at least 3 weeks with uncertain diagnosis after a number of obligatory investigations. The differential diagnosis of FUO can be subdivided in four categories: infections, malignancies, noninfectious inflammatory diseases, and miscellaneous causes. In most cases of FUO, there is an uncommon presentation of a common disease. FDG-PET/CT is a sensitive diagnostic technique for the evaluation of FUO by facilitating anatomical localization of focally increased FDG uptake, thereby guiding further diagnostic tests to achieve a final diagnosis. FDG-PET/CT should become a routine procedure in the workup of FUO when diagnostic clues are absent. FDG-PET/CT appears to be a cost-effective routine imaging technique in FUO by avoiding unnecessary investigations and reducing the duration of hospitalization.

[Not Available]

Zusammenfassung. Wir berichten über einen 58-jährigen Patienten mit seit Monaten bestehender B-Symptomatik, rezidivierenden Fieberschüben begleitet von Kopfschmerzen und erhöhten Entzündungsparametern. In der Erstlinienabklärung ergaben sich keine eindeutigen Hinweise auf eine infektiologische oder rheumatologische Ursache, auffällig war lediglich eine mediastinale und hiläre Lymphadenopathie. Zum Ausschluss eines Malignoms wurde eine PET-CT durchgeführt, in der sich eine FDG-Aufnahme im Bereich der grossen Gefässe zeigte, passend zu einer Riesenzellarteritis. Bei eindeutigem Befund konnte auf einen Temporalarterienbiopsie verzichtet und eine Therapie mit Glukokortikoiden begonnen werden.