Fever of unknown origin (FUO). II. Diagnostic procedures in a prospective multicenter study of 167 patients. The Netherlands FUO Study Group

Recommendations for Updating Fever and Inflammation of Unknown Origin From a Modified Delphi Consensus Panel

Background

Fever of unknown origin (FUO) and inflammation of unknown origin (IUO) are syndromes commonly used as medical diagnoses. Since the existing literature has a mixture of diagnostic approaches, developing consensus-based recommendations would be helpful for clinicians, researchers, and patients.

Methods

A modified Delphi process was performed from October 2022 to July 2023, involving 4 rounds of online surveys and 2 live video conferences. The panel comprised international experts recruited based on peer-reviewed published publications and studies.

Results

Among 50 invited experts, 26 (52.0%) agreed to participate. Twenty-three panelists completed round 1 of the survey, 21 completed rounds 2 and 3, 20 completed round 4, and 7 participated in round 5 live video discussions. Of the participants, 18 (78.3%) were academic-based clinicians and researchers, 5 (21.7%) practiced in a community-based hospital, and 6 (26.1%) were female. Consensus was reached on 5 themes: (1) incorporating epidemiologic factors, such as geographic location and travel history; (2) updated criteria for classifying FUO or IUO; (3) initial evaluation approaches; (4) a classification system for diagnoses; and (5) recommendations for judicious limitation of empiric therapies. Experts strongly disagreed with using 2-deoxy-2-[18F] fluoro-D-glucose positron emission tomography/computed tomography as part of the diagnostic criteria for FUO. There were mixed opinions about the importance of the temperature measurement site, the 3-week minimum illness criterion, the need for a standard definition of relapsing fevers, and the use of similar evaluation strategies for FUO and IUO.

Conclusions

These Delphi-generated consensus-based recommendations offer potential improvements compared with earlier definitions and a guide for clinical practice and future research.

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.

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.

Geographic Upon Noninfectious Diseases Accounting for Fever of Unknown Origin (FUO): A Systematic Review and Meta-analysis

Background

Diagnostic outcomes for fever of unknown origin (FUO) remain with notable numbers of undiagnosed cases. A recent systemic review and meta-analysis of studies reported geographic variation in FUO-related infectious diseases. Whether geography influences types of FUO noninfectious diagnoses deserves examination.

Methods

Medline (PubMed), Embase, Scopus, and Web of Science databases were searched systematically using medical subject headings published from January 1, 1997, to March 31, 2021. Prospective clinical studies investigating participants meeting adult FUO defining criteria were selected if they assessed final diagnoses. Meta-analyses were based on the random-effects model according to World Health Organization (WHO) geographical regions.

Results

Nineteen studies with significant heterogeneity were analyzed, totaling 2,667 participants. Noninfectious inflammatory disorders had a pooled estimate at 20.0% (95%CI: 17.0-23.0%). Undiagnosed illness had a pooled estimate of 20.0% (95%CI: 14.0-26.0%). The pooled estimate for cancer was 15.0% (95%CI: 12.0-18.0%). Miscellaneous conditions had a pooled estimate of 6.0% (95%CI: 4.0-8.0%). Noninfectious inflammatory disorders and miscellaneous conditions were most prevalent in the Western Pacific region with a 27.0% pooled estimate (95%CI: 20.0-34.0%) and 9.0% (95%CI: 7.0-11.0%), respectively. The highest pooled estimated for cancer was in the Eastern Mediterranean region at 25.0% (95%CI: 18.0-32.0%). Adult-onset Still’s disease (114 [58.5%]), systemic lupus (52 [26.7%]), and giant-cell arteritis (40 [68.9%]) predominated among the noninfectious inflammatory group. Lymphoma (164 [70.1%]) was the most common diagnosis in the cancer group.

Conclusions

In this systematic review and meta-analysis, noninfectious disease diagnostic outcomes varied among WHO-defined geographies. Evaluation of FUO should consider local variations in disease prevalence.

Prospective Studies Comparing Structured vs Nonstructured Diagnostic Protocol Evaluations Among Patients With Fever of Unknown Origin: A Systematic Review and Meta-analysis

Importance

Patients meeting the criteria for fever of unknown origin (FUO) can be evaluated with structured or nonstructured approaches, but the optimal diagnostic method is unresolved.

Objective

To analyze differences in diagnostic outcomes among patients undergoing structured or nonstructured diagnostic methods applied to prospective clinical studies.

Data Sources

PubMed, Embase, Scopus, and Web of Science databases with librarian-generated query strings for FUO, PUO, fever or pyrexia of unknown origin, clinical trial, and prospective studies identified from January 1, 1997, to March 31, 2021.

Study Selection

Prospective studies meeting any adult FUO definition were included. Articles were excluded if patients did not precisely fit any existing adult FUO definition or studies were not classified as prospective.

Data Extraction and Synthesis

Abstracted data included years of publication and study period, country, setting (eg, university vs community hospital), defining criteria and category outcome, structured or nonstructured diagnostic protocol evaluation, sex, temperature threshold and measurement, duration of fever and hospitalization before final diagnoses, and contribution of potential diagnostic clues, biochemical and immunological serologic studies, microbiology cultures, histologic analysis, and imaging studies. Structured protocols compared with nonstructured diagnostic methods were analyzed using regression models.

Main Outcomes and Measures

Overall diagnostic yield was the primary outcome.

Results

Among the 19 prospective trials with 2627 unique patients included in the analysis (range of patient ages, 10-94 years; 21.0%-55.3% female), diagnoses among FUO series varied across and within World Health Organization (WHO) geographic regions. Use of a structured diagnostic protocol was not significantly associated with higher odds of yielding a diagnosis compared with nonstructured protocols in aggregate (odds ratio [OR], 0.98; 95% CI, 0.65-1.49) or between Western Europe (Belgium, France, the Netherlands, and Spain) (OR, 0.95; 95% CI, 0.49-1.86) and Eastern Europe (Turkey and Romania) (OR, 0.83; 95% CI, 0.41-1.69). Despite the limited number of studies in some regions, analyses based on the 6 WHO geographic areas found differences in the diagnostic yield. Western European studies had the lowest percentage of achieving a diagnosis. Southeast Asia led with infections at 49.0%. Noninfectious inflammatory conditions were most prevalent in the Western Pacific region (34.0%), whereas the Eastern Mediterranean region had the highest proportion of oncologic explanations (24.0%).

Conclusions and Relevance

In this systematic review and meta-analysis, diagnostic yield varied among WHO regions. Available evidence from prospective studies did not support that structured diagnostic protocols had a significantly better rate of achieving a diagnosis than nonstructured protocols. Clinicians worldwide should incorporate geographical disease prevalence in their evaluation of patients with FUO.

Geographic Variation of Infectious Disease Diagnoses Among Patients with Fever of Unknown Origin (FUO) – A Systematic Review and Meta-analysis

Background

Fever of unknown origin (FUO) investigations yield a substantial number of patients with infectious diseases. This systematic review and meta-analysis aimed to quantify more common FUO infectious diseases etiologies and to underscore geographic variation.

Methods

Four databases (PubMed, Embase, Scopus, and Web of Science) were searched for prospective studies reporting FUO rates among adult patients from 1 January 1997 to 31 March 2021. The pooled proportion for infectious diseases etiology was estimated using the random-effects meta-analysis model.

Results

Nineteen prospective studies were included with 2667 total cases. No studies were available for Africa or the Americas. Overall, 37.0% (95.0% confidence interval [CI], 30.0%–44.0%) of FUO patients had an infectious disease etiology. Infections were more likely from Southeastern Asia (pooled proportion, 0.49 [95% CI, .43–.55]) than from Europe (pooled proportion, 0.31 [95% CI, .22–.41]). Among specifically reported infectious diseases (n = 832), Mycobacterium tuberculosis complex predominated across all geographic regions (n = 285 [34.3%]), followed by brucellosis (n = 81 [9.7%]), endocarditis (n = 62 [7.5%]), abscesses (n = 61 [7.3%]), herpesvirus (eg, cytomegalovirus and Epstein-Barr virus) infections (n = 60 [7.2%]), pneumonia (n = 54 [6.5%]), urinary tract infections (n = 54 [6.5%]), and enteric fever (n = 40 [4.8%]).

Conclusions

FUO patients from Southeastern Asia were more likely to have an infectious diseases etiology when compared to other regions. The predominant factor for this finding appears to be differences in disease prevalence among various geographical locations or other factors such as access to timely care and diagnosis. Noting epidemiological disease factors in FUO investigations could improve diagnostic yields and clinical outcomes.

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.

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.

Usefulness of computed tomography for hospitalized adult patients with fever to investigate cause of fever: single-center, retrospective cohort study

Purpose

To verify that physicians’ presumptive diagnosis is the most significant factor for finding any signs related to the cause of fever on computed tomography (CT) images.

Materials and methods

This single-center retrospective cohort study included patients (age ≥ 16 years) who underwent CT to investigate the cause of fever between January 1, 2014, and August 31, 2016. Patients who underwent surgical procedures were excluded. The primary outcome was the presence of suspicious CT findings related to the cause of fever. We performed univariate and multivariate logistic regression analyses, adjusted for CT contrast agent use, quick sequential organ failure assessment score > 1, and C-reactive protein level.

Results

We enrolled 171 patients, of which 57 had CT findings, and 114 did not. Multivariate logistic regression analyses demonstrated a significant difference for the presence of a presumptive diagnosis by the attending physician (odds ratio, 4.99; 95% confidence interval 2.31–10.76; p < 0.01), but not for other covariates, including C-reactive protein.

Conclusions

In hospitalized patients with fever, an attending physicians’ presumptive diagnosis is associated with the presence of fever-related CT findings. Improving the quality of the diagnostic assessment before the CT scan may lead to more appropriate CT imaging use.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11604-021-01117-5.

Imaging a Fever-Redefining the Role of 2-deoxy-2-[18F]Fluoro-D-Glucose-Positron Emission Tomography/Computed Tomography in Fever of Unknown Origin Investigations

Growing evidence suggests that 2-deoxy-2-[18F]fluoro-D-glucose (18FDG)-positron emission tomography/computed tomography (PET/CT) is a useful imaging technique for the evaluation of fever of unknown origin (FUO). This imaging technique allows for accurate localization of foci of hypermetabolism based on 18FDG uptake in glycolytically active cells that may represent inflammation, infection, or neoplasia. The presence of abnormal uptake can help direct further investigation that may yield a final diagnosis. A lack of abnormal uptake can be reasonably reassuring that these conditions are not present, thereby avoiding unnecessary additional testing. Insurers have not routinely covered outpatient 18FDG-PET/CT for the indication of FUO in the United States. However, data published since 2007 suggest early use in FUO diagnostic evaluations improves diagnostic efficiency and reduces costs. Clinicians and insurers should consider 18FDG-PET/CT as a useful tool when preliminary studies are unrevealing.

Progress Report: Next-Generation Sequencing (NGS), Multiplex Polymerase Chain Reaction (PCR), and Broad-Range Molecular Assays as Diagnostic Tools for Fever of Unknown Origin (FUO) Investigations in Adults

Even well into the 21st century, infectious diseases still account for most causes of fever of unknown origin (FUO). Advances in molecular technologies, including broad-range PCR of the 16S rRNA gene followed by Sanger sequencing, multiplex PCR assays, and more recently, next-generation sequencing (NGS) applications, have transitioned from research methods to more commonplace in some clinical microbiology laboratories. They have the potential to supplant traditional microbial identification methods and antimicrobial susceptibility testing. Despite the remaining challenges with these technologies, publications in the past decade justify excitement about the potential to transform FUO investigations. We discuss available evidence using these molecular methods for FUO evaluations, including potential cost-benefits and future directions.

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.

Fever and Fever of Unknown Origin: Review, Recent Advances, and Lingering Dogma

Fever has preoccupied physicians since the earliest days of clinical medicine. It has been the subject of scrutiny in recent decades. Historical convention has mostly determined that 37.0°C (98.6°F) should be regarded as normal body temperature, and more modern evidence suggests that fever is a complex physiological response involving the innate immune system and should not be characterized merely as a temperature above this threshold. Fever of unknown origin (FUO) was first defined in 1961 by Petersdorf and Beeson and continues to be a clinical challenge for physicians. Although clinicians may have some understanding of the history of clinical thermometry, how average body temperatures were established, thermoregulation, and pathophysiology of fever, new concepts are emerging. While FUO subgroups and etiologic classifications have remained unchanged since 1991 revisions, the spectrum of diseases, clinical approach to diagnosis, and management are changing. This review considers how newer data should influence both definitions and lingering dogmatic principles. Despite recent advances and newer imaging techniques such as 18-fluorodeoxyglucose-positron emission tomography, clinical judgment remains an essential component of care.

The changing pattern of fever of unknown origin in the Republic of North Macedonia

INTRODUCTION

The study aimed to compare the etiologic spectrum of diseases causing fever of unknown origin (FUO) and methods for definitive diagnosis in a tertiary care hospital in the Republic of North Macedonia during two different time periods.

PATIENTS AND METHODS

There were analysed retrospectively the causes for FUO and final diagnostic approaches in 185 patients with classic FUO that were treated at the University Hospital for Infectious Diseases in Skopje during two time periods. Seventy nine patients were treated during 1991 to 1995 and 106 patients during 2011 to 2015.

RESULTS

When comparing these two periods, infections were present in 46.8% and 29.2% (p = 0.014), non-infective inflammatory disorders in 22.8% and 25.5% (p = 0.674), neoplasms in 10.1% and 13.2% (p = 0.522), miscellaneous in 8.9% and 12.3% (p = 0.461) and undiagnosed cases in 11.4% and 19.8% (p = 0.124), respectively. The most common causes for FUO during the first period were abscesses (8.9%), tuberculosis and systemic lupus erythematosus (7.6% each), whereas in the second period the commonest causes were adult onset Still disease and solid organ neoplasm (7.6% each), polymyalgia rheumatica, abscesses and visceral leishmaniasis (5.7% each). The newer imaging techniques and clinical course evaluation had superior diagnostic significance during the second period.

CONCLUSION

A changing pattern of diseases causing FUO during the examined periods was evident. Infections continue to be the most common cause but with decreasing incidence when compared to 20 years ago. Even nowadays clinical evaluation and follow-up still remain the vital diagnostic tools in determining the etiology of FUO.

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.

Radionuclide Imaging of Infection and Inflammation in Children: a Review

With the exception of radiolabeled monoclonal antibodies, antibody fragments and radiolabeled peptides which have seen little application in the pediatric population, the nuclear medicine imaging procedures used in the evaluation of infection and inflammation are the same for both adults and children. These procedures include (1) either a two- or a three-phase bone scan using technetium-99m methylene diphosphonate; (2) Gallium 67-citrate; (3) in vitro radiolabeled white blood cell imaging (using ¹¹¹Indium-oxine or ^99mTechnetium hexamethyl-propylene-amine-oxime-labeled white blood cells); and (4) hybrid imaging with ¹⁸F-FDG. But children are not just small adults. Not only are the disease processes encountered in children different from those in adults, but there are developmental variants that can mimic, but should not be confused with, pathology. This article discusses some of the differences between adults and children with osteomyelitis, illustrates several of the common developmental variants that can mimic disease, and, finally, focuses on the increasing use of ¹⁸F-FDG PET/CT in the diagnosis and response monitoring of children with infectious and inflammatory processes. The value of and need for pediatric specific imaging protocols are reviewed.

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.

The efficacy of 18F-FDG PET/CT and 67Ga SPECT/CT in diagnosing fever of unknown origin

OBJECTIVE

Fever of unknown origin (FUO) is a diagnostic challenge. This study aimed to assess the efficacy of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and gallium-67 single-photon emission computed tomography/computed tomography (⁶⁷Ga SPECT/CT) in diagnosing FUO.

METHODS

A total of 68 patients with FUO underwent ¹⁸F-FDG PET/CT and ⁶⁷Ga SPECT/CT from January 2013 through May 2016. Images were read independently. The imaging results were compared with the final diagnosis and categorized as helpful for diagnosis or non-contributory to diagnosis in the clinical setting. Associations between categorical variables were evaluated with the chi-square test or Fisher's exact test.

RESULTS

Ten of the 68 patients were excluded. An infectious underlying disease was found in 23 patients. A malignant disorder was the cause of FUO in 10 patients. Non-infectious inflammatory disease was found in 11 patients. Adrenal insufficiency was the cause of FUO in two patients. The cause of FUO was not found for 12 patients. A high false-positive rate of 44% (7/16) was observed for ¹⁸F-FDG PET/CT, while a high false-negative rate of 55% (23/42) was observed for ⁶⁷Ga SPECT/CT. ¹⁸F-FDG PET/CT studies depicted all ⁶⁷Ga-avid lesions. The sensitivity (79% vs. 45%) and clinical contribution (72% vs. 55%) of ¹⁸F-FDG PET/CT in diagnosing FUO were significantly higher than those of ⁶⁷Ga SPECT/CT (p<0.05).

CONCLUSIONS

On the basis of this study, the diagnostic performance of ¹⁸F-FDG PET/CT is superior to ⁶⁷Ga SPECT/CT in the work-up of patients with FUO. With its rapid results and superior sensitivity, ¹⁸F-FDG PET/CT may replace ⁶⁷Ga SPECT/CT where this technique is available.

Key diagnostic features of fever of unknown origin: Medical history and physical findings

Background

Fever of unknown origin (FUO) has many possible causes, so detailed history taking and physical examination are required. We identified key diagnostic features of medical history and physical findings for an efficient diagnosis of FUO.

Methods

A total of 42 consecutive patients (mean age: 50.6±20.3 years) with classic FUO were retrospectively recruited from January 2010 to March 2012. Key diagnostic features were identified from among diagnostic criteria for underlying diseases, indicators for diagnostic tests, and more useful factors for differential diagnosis.

Results

The mean number of abnormal findings per patient was 5.8 from taking the history and 2.0 from performing physical examination. In addition, the mean number of key diagnostic features identified was 0.7 (14.0%) from history taking and 0.6 (35.0%) from physical examination. The most relevant key diagnostic feature was arthritis, followed by cervical lymphadenopathy, dyspnea (with hypoxia), and ocular symptoms.

Conclusion

The usefulness of certain features of medical history and physical findings for diagnosing FUO was determined. Focusing on arthritis, cervical lymphadenopathy, dyspnea with hypoxia, and ocular symptoms might improve diagnostic efficiency in patients with FUO.

Fever of unknown origin (FUO) revised

Fever of unknown origin (FUO) was originally characterised in 1961 by Petersdorf and Beeson as a disease condition of temperature exceeding 38.3 °C on at least three occasions over a period of at least three weeks, with no diagnosis made despite one week of inpatient investigation. However, since underlying diseases are often reported for classical FUO, these presentations may not be considered to be of “unknown origin”. Rather, the aetiology of prolonged fever may resolve, or not resolve. The definition of fever with unresolved cause (true FUO) is difficult, as it is a moving target, given the constant advancement of imaging and biomarker analysis. Therefore, the prevalence of fever with unresolved cause (FUO) is unknown.

In this review, we report such a case of prolonged fever, which initially has presented as classical FUO, and discuss current literature. Furthermore, we will give an outlook, how a prospective study on FUO will allow to solve outstanding issues like the utility of different diagnostic investigations, and the types and prevalence of various underlying diseases.

Diagnosis and management of undifferentiated fever in children

The incidence and likely causes of fever of unknown origin (FUO) have changed over the last few decades, largely because enhanced capabilities of laboratory testing and imaging have helped confirm earlier diagnoses. History and examination are still of paramount importance for cryptogenic infections. Adolescents who have persisting nonspecific complaints of fatigue sometimes are referred to Pediatric Infectious Diseases consultants for FUO because the problem began with an acute febrile illness or measured temperatures are misidentified as "fevers". A thorough history that reveals myriad symptoms when juxtaposed against normal findings on examination and simple laboratory testing can suggest a diagnosis of "fatigue of deconditioning". "Treatment" is forced return to school, and reconditioning. The management of patients with acute onset of fever without an obvious source or focus of infection is dependent on age. Infants under one month of age are at risk for serious and rapidly progressive bacterial and viral infections, and yet initially can have fever without other observable abnormalities. Urgent investigation and pre-emptive therapies usually are prudent. By two months of age, clinical judgment best guides management. Between one and two months of age, a decision to investigate or not depends on considerations of the height and duration of fever, the patient's observable behavior/interaction, knowledge of concurrent family illnesses, and likelihood of close observation and follow up. Children 6 months-36 months of age with acute onset of fever who appear well and have no observable focus of infection can be evaluated clinically, without laboratory investigation or antibiotic therapy, unless risk factors elevate the likelihood of urinary tract infection.

Fever of unknown origin: a clinical approach

Fevers of unknown origin remain one of the most difficult diagnostic challenges in medicine. Because fever of unknown origin may be caused by over 200 malignant/neoplastic, infectious, rheumatic/inflammatory, and miscellaneous disorders, clinicians often order non-clue-based imaging and specific testing early in the fever of unknown origin work-up, which may be inefficient/misleading. Unlike most other fever-of-unknown-origin reviews, this article presents a clinical approach. Characteristic history and physical examination findings together with key nonspecific test abnormalities are the basis for a focused clue-directed fever of unknown origin work-up.

Fever of unknown origin

More than 50 years after the first definition of fever of unknown origin (FUO), it still remains a diagnostic challenge. Evaluation starts with the identification of potential diagnostic clues (PDCs), which should guide further investigations. In the absence of PDCs a standardised diagnostic protocol should be followed with PET-CT as the imaging technique of first choice. Even with a standardised protocol, in a large proportion of patients from western countries the cause for FUO cannot be identified. The treatment of FUO is guided by the final diagnosis, but when no cause is found, antipyretic drugs can be prescribed. Corticosteroids should be avoided in the absence of a diagnosis, especially at an early stage. The prognosis of FUO is determined by the underlying cause. The majority of patients with unexplained FUO will eventually show spontaneous remission of fever. We describe the definition, diagnostic workup, causes and treatment of FUO.

30 years hids-Travels between bedside and bench

In this paper I describe more than 30 years of investigations of the autoinflammatory syndrome hyper-IgD syndrome (HIDS). In the first paper after the recognition of the syndrome published in 1984, we described the characteristics of this periodic fever syndrome. The hypotheses regarding the pathogenesis of the fever and the acute phase response in these patients prompted us to study interleukin-1 (IL-1), the cytokine formerly described as endogenous pyrogen and lymphocyte activating factor. Although we were unable to find elevated concentrations of IL-1 in the circulation, we discovered that white blood cells spontaneously produced elevated amounts of IL-1b. A major next discovery was the identification of the gene defect by us and others in 1999: quite unexpectedly the mevalonate kinase, an enzyme in the cholesterol synthesis pathway was found to be mutated. We were able to describe a founder effect and a phenotypic continuum with the classical mevalonate aciduria in the years to follow. A major step forward was the finding that recombinant interleukin-1 receptor antagonist (anakinra) was an effective treatment for the majority of patients. Thus, research over a period of three decades after the first recognition of the syndrome, has yielded much insight into the pathogenesis as well as an effective therapy for HIDS.

[Diagnostic approach of recurrent fevers of unknown origin in adults]

Recurrent fever of unknown origin is probably the most difficult to diagnose subtype of fever of unknown origin. It represents between 18 and 42% of the cases in large series of patients with fever of unknown origin. The limited literature data do not allow one to construct a diagnostic algorithm. However, the diagnostic strategy is different from classic fever of unknown origin. The spectrum of causative disorders is different from continuous fever with less infections and tumors. Among systemic inflammatory diseases, adult-onset Still's disease is the most common cause. More than 50% of the cases remain unexplained. Hereditary recurrent fevers, the prototype of autoinflammatory diseases, are now more easily discuss in a young adult.

Clinical utility of indium 111-labeled white blood cell scintigraphy for evaluation of suspected infection

We assessed the clinical utility of indium 111–labeled white blood cell scans at our tertiary referral center from 2005 to 2011. Overall, scans meaningfully impacted clinical care <50% of the time. Scan utility was greater for suspected vascular graft infections or osteomyelitis.

Background

 We sought to characterize the clinical utility of indium 111 (¹¹¹In)–labeled white blood cell (WBC) scans by indication, to identify patient populations who might benefit most from this imaging modality.

Methods

 Medical records for all patients who underwent ¹¹¹In-labeled WBC scans at our tertiary referral center from 2005 to 2011 were reviewed. Scan indication, results, and final diagnosis were assessed independently by 2 infectious disease physicians. Reviewers also categorized the clinical utility of each scan as helpful vs not helpful with diagnosis and/or management according to prespecified criteria. Cases for which clinical utility could not be determined were excluded from the utility assessment.

Results

 One hundred thirty-seven scans were included in this analysis; clinical utility could be determined in 132 (96%) cases. The annual number of scans decreased throughout the study period, from 26 in 2005 to 13 in 2011. Forty-one (30%) scans were positive, and 85 (62%) patients were ultimately determined to have an infection. Of the evaluable scans, 63 (48%) scans were deemed clinically useful. Clinical utility varied by scan indication: ¹¹¹In-labeled WBC scans were more helpful for indications of osteomyelitis (35/50, 70% useful) or vascular access infection (10/15, 67% useful), and less helpful for evaluation of fever of unknown origin (12/35, 34% useful).

Conclusions

 ¹¹¹In-labeled WBC scans were useful for patient care less than half of the time at our center. Targeted ordering of these scans for indications in which they have greater utility, such as suspected osteomyelitis and vascular access infections, may optimize test utilization.

The management and the diagnosis of fever of unknown origin

Prolonged fever presents a challenge for the patient and the physician. Fever with a temperature higher than 38.3°C on several occasions that lasts for at least 3 weeks and lacks a clear diagnosis after 1 week of study in the hospital is called a fever of unknown origin (FUO). More than 200 diseases can cause FUO, and the information gathered from history taking, physical examination, laboratory and imaging studies should be evaluated with care. History taking and physical examination may provide some localizing signs and symptoms pointing toward a diagnosis. Infection, cancers, noninfectious inflammatory diseases and some miscellaneous diseases are the main etiologies, and some patients remain undiagnosed despite investigations. Tuberculosis, lymphoma and adult-onset Still's disease are the main diseases. Fluorodeoxyglucose PET is a promising imaging modality in FUO. Establishing a uniform algorithm for FUO management is difficult. Every patient should be carefully evaluated individually considering the previous FUO management experience.

Persistent hypertransaminasemia in asymptomatic children: A stepwise approach

We aimed to examine the major causes of isolated chronic hypertransaminasemia in asymptomatic children and develop a comprehensive diagnostic flow diagram. A MEDLINE search inclusive of publications throughout August 2012 was performed. We found only a small number of publications that had comprehensively investigated this topic. Consequently, it was difficult to construct a diagnostic flowchart similar to those already available for adults. In children, a “retesting panel” prescription, including gamma-glutamyl transpeptidase and creatine kinase in addition to aminotransferases, is considered a reasonable approach for proficiently confirming the persistence of the abnormality, ruling out cholestatic hepatopathies and myopathies, and guiding the subsequent diagnostic steps. If re-evaluation of physical and historical findings suggests specific etiologies, then these should be evaluated in the initial enzyme retesting panel. A simple multi-step diagnostic algorithm incorporating a large number of possible pediatric scenarios, in addition to the few common to adults, is available. Accurately classifying a child with asymptomatic persistent hypertransaminasemia may be a difficult task, but the results are critical for preventing the progression of an underlying, possibly occult, condition later in childhood or during transition. Given the high benefit/cost ratio of preventing hepatic deterioration, no effort should be spared in diagnosing and properly treating each case of persistent hypertransaminasemia in pediatric patients.

Unexplained recurrent fever: when is autoinflammation the explanation?

Recurrent fever can be the sole or leading manifestation of a variety of diseases including malignancies, autoimmune diseases and infections. Because the differential diagnoses are manifold, no formal guidelines for the approach of patients with recurrent fever exists. The newly recognized group of autoinflammatory diseases are often accompanied by repetitive fever attacks. As these episodes are frequently associated by a variety of divergent presentations, the differentiation of other causes for febrile illnesses can be difficult. In this article, we first review disease entities, which frequently present with the symptom of recurrent fever. In a next step, we summarize their characteristic pattern of disease presentation. Finally, we analyse key features of autoinflammatory diseases, which are helpful to distinguish this group of diseases from the other causes of recurrent fever. Recognizing these symptom patterns can provide the crucial clues and, thus, lead to the initiation of targeted specific diagnostic tests and therapies.

A Rationale for the Use of F18-FDG PET/CT in Fever and Inflammation of Unknown Origin

This review focuses on the diagnostic value of hybrid F18-FDG Positron Emission Tomography/Computerized tomography (PET/CT) in fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Due to the wide range of possible causes both FUO and IUO remain a clinical challenge for both patients and physicians. In addition, the aetiology of IUO shows the same variation in diseases as the FUO spectrum and probably requires the same diagnostic approach as FUO. There are numerous historically used diagnostic approaches incorporating invasive and non-invasive, and imaging techniques, all with relative high specificity but limited sensitivity. This hampers the generalization of these diagnostic approaches. However, recently published reports show that F18-FDG PET/CT in FUO and IUO has a high sensitivity and a relative non-specificity for malignancy, infection and inflammation. This makes F18-FDG PET/CT an ideal diagnostic tool to start the diagnostic process and to guide subsequent focused diagnostic approaches with higher specificity. In addition, F18-FDG PET/CT has a relative high negative predictive value. Therefore F18 FDG PET/CT should be incorporated in the routine diagnostic work-up of patients with FUO and IUO, preferably at an early stage in the diagnostic process.

The role of invasive and non-invasive procedures in diagnosing fever of unknown origin

BACKGROUND

The etiology of fever of unknown origin has changed because of the recent advances in and widespread use of invasive and non-invasive diagnostic tools. However, undiagnosed patients still constitute a significant number.

OBJECTIVE

To determine the etiological distribution and role of non-invasive and invasive diagnostic tools in the diagnosis of fever of unknown origin.

MATERIALS & METHODS

One hundred patients who were hospitalized between June 2001 and 2009 with a fever of unknown origin were included in this study. Clinical and laboratory data were collected from the patients' medical records retrospectively.

RESULTS

Fifty three percent of the patients were male, with a mean age of 45 years. The etiology of fever was determined to be infectious diseases in 26, collagen vascular diseases in 38, neoplastic diseases in 14, miscellaneous in 2 and undiagnosed in 20 patients. When the etiologic distribution was analyzed over time, it was noted that the rate of infectious diseases decreased, whereas the rate of rheumatological and undiagnosed diseases relatively increased because of the advances in imaging and microbiological studies. Seventy patients had a definitive diagnosis, whereas 10 patients had a possible diagnosis. The diagnoses were established based on clinical features and non-invasive tests for 61% of the patients and diagnostic benefit was obtained for 49% of the patients undergoing invasive tests. Biopsy procedures contributed a rate of 42% to diagnoses in patients who received biopsies.

CONCLUSION

Clinical features (such as detailed medical history-taking and physical examination) may contribute to diagnoses, particularly in cases of collagen vascular diseases. Imaging studies exhibit certain pathologies that guide invasive studies. Biopsy procedures contribute greatly to diagnoses, particularly for malignancies and infectious diseases that are not diagnosed by non-invasive procedures.

[Analysis of cost-effectiveness in the diagnosis of fever of unknown origin and the role of (18)F-FDG PET-CT: a proposal of diagnostic algorithm]

AIM

To analyze the costs of Fever of Unknown Origin (FUO) prior to the PET-CT study. To determine the effectiveness of PET-CT in the diagnosis of FUO. A proposal of diagnostic algorithm.

MATERIAL AND METHODS

A retrospective study was performed that included 20 patients who had been studied between January 2007 and January 2011, with a mean age of 57.75 years and FUO diagnosis. All underwent a PET-CT study with (18)F-FDG. Individual and mean costs of FUO in these patients were assessed, including hospitalization days and complementary tests prior to the PET-CT study. The effectiveness of the PET-CT study in the diagnosis of FUO was analyzed. Costs of the FUO process were determined, including those of the PET-CT study, and if it had been done earlier in the diagnostic process.

RESULTS

Mean hospital stay per patient until the PET-CT study was 28 days. The cost per hospitalization day was 342 €. Average cost per patient in complementary tests was 1395 €. Total cost of the FUO process until the PET-CT study was around 11167 € per patient. The PET-CT study showed a 78% sensitivity, 83% specificity, 92% PPV and 62% NPV. If PET-CT had been performed earlier in the FUO process, assuming the same effectiveness, 5471 € per patient would have been saved.

CONCLUSION

The PET-CT study could be cost-effective in the FUO process if used at an early stage, helping to establish an early diagnosis, reducing hospitalization days due to diagnostic purposes and the repetition of unnecessary tests.

Functional imaging of infection: conventional nuclear medicine agents and the expanding role of 18-F-FDG PET

A growing body of literature suggests that 18-fluorine fluorodeoxyglucose positron emission tomography ((18)F-FDG PET), particularly when combined with CT, is a useful tool for the detection of infectious and inflammatory disease processes. This article will briefly review the data to date on the use of FDG PET in diagnosing musculoskeletal infections and fever of unknown origin, comparing it to conventional scintigraphic techniques in both adults and, when available, in children.

FDG-PET or PET/CT in Fever of Unknown Origin: The Diagnostic Role of Underlying Primary Disease

Fever of unknown origin (FUO) is generally defined as a fever greater than 38.3°C on several occasions during a period longer than 3 weeks for which the etiology behind cannot be diagnosed at the end of at least 1 week hospital stay. Conventional diagnostic methods are still not adequate to reveal underlying reason in approximately 50% of patients with FUO. In patients with certain diagnosis, three major categories are infections, malignancies, and noninfectious inflammatory diseases. Fluoro-18-fluoro-2-deoxy-D-glucose (FDG) is a structural analog of 2-deoxyglucose and accumulates in malignant tissues but also at sites of infection and inflammation. For this reason, FDG PET or PET/CT has great advantage in understanding of underlying pathology in assessment of FUO. However, till today, there are limited studies about the role of FDG PET or PET/CT in evaluation of FUO. In this paper, the impact of FDG PET or PET/CT in the diagnostic work-up of FUO is described by data obtained from literature review.

Fever of unknown origin: discrimination between infectious and non-infectious causes

OBJECTIVE

The present study aimed to develop and evaluate a simple diagnostic model that could aid physicians to discriminate between infectious and non-infectious causes of fever of unknown origin (FUO).

DESIGN/SETTING/SUBJECTS

Patients with classical FUO were studied in two distinct, prospective, observational phases. In the derivation phase that lasted from 1992 to 2000, 33 variables regarding demographic characteristics, history, symptoms, signs, and laboratory profile were recorded and considered in a logistic regression analysis using the diagnosis of infection as a dependent variable. In the validation phase, the discriminatory capacity of a score based on the derived predictors of infection was calculated for FUO patients assessed from 2001 to 2007.

RESULTS

Data from 112 individuals (mean age 56.5+/-11.2 years) were analyzed in the derivation cohort. The final diagnoses included infections, malignancies, non-infectious inflammatory diseases, and miscellaneous conditions in 30.4%, 10.7%, 33% and 5.4% of subjects, whereas 20.5% of cases remained undiagnosed. C-reactive protein>60 mg/L (odds ratio 6.0 [95% confidence intervals 2.5, 9.8]), eosinophils<40/mm(3) (4.1 [2.0, 7.3]) and ferritin<500 microg/L (2.5 [1.3, 5.2]) were independently associated with diagnosis of infection. Among the 100 patients of the validation cohort, the presence of > or =2 of the above factors predicted infection with sensitivity, specificity, and positive and negative predictive values of 91.4%, 92.3%, 86.5%, and 95.2%, respectively.

CONCLUSIONS

The combination of C-reactive protein, ferritin and eosinophil count may be useful in discriminating infectious from non-infectious causes in patients hospitalised for classical FUO.