Fever of unknown origin in a Mediterranean survey from a division of internal medicine: report of 91 cases during a 12-year-period (1991-2002)

Rheumatic disorders among patients with fever of unknown origin: A systematic review and meta-analysis

OBJECTIVES

To conduct a systematic literature review and meta-analysis to estimate the proportion of fever of unknown origin (FUO) and inflammation of unknown origin (IUO) cases that are due to rheumatic disorders and the relative frequency of specific entities associated with FUO/IUO.

METHODS

We searched PubMed and EMBASE between January 1, 2002, and December 31, 2021, for studies with ≥50 patients reporting on causes of FUO/IUO. The primary outcome was the proportion of FUO/IUO patients with rheumatic disease. Secondary outcomes include the association between study and patient characteristics and the proportion of rheumatic disease in addition to the relative frequency of rheumatic disorders within this group. Proportion estimates were calculated using random-effects models.

RESULTS

The included studies represented 16884 patients with FUO/IUO. Rheumatic disease explained 22.2% (95%CI 19.6 - 25.0%) of cases. Adult-onset Still's disease (22.8% [95%CI 18.4-27.9%]), giant cell arteritis (11.4% [95%CI 8.0-16.3%]), and systemic lupus erythematosus (11.1% [95%CI 9.0-13.8%]) were the most frequent disorders. The proportion of rheumatic disorders was significantly higher in high-income countries (25.9% [95%CI 21.5 - 30.8%]) versus middle-income countries (19.5% [95%CI 16.7 - 22.7%]) and in prospective studies (27.0% [95%CI 21.9-32.8%]) versus retrospective studies (20.6% [95%CI 18.1-24.0%]). Multivariable meta-regression analysis demonstrated that rheumatic disease was associated with the fever duration (0.011 [95%CI 0.003-0.021]; P=0.01) and with the fraction of patients with IUO (1.05 [95%CI 0.41-1.68]; P=0.002).

CONCLUSION

Rheumatic disorders are a common cause of FUO/IUO. The care of patients with FUO/IUO should involve physicians who are familiar with the diagnostic workup of rheumatic disease.

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.

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.

Pyrexia of unknown origin associated with a non-infected vaginal shelf pessary

An 82-year-old female was admitted with pyrexia and rigors. Bloods showed a raised C-reactive protein and she was commenced on empirical intravenous antibiotics. Chest X-ray, urine microscopy and computed tomography scan of the patient's abdomen and pelvis did not demonstrate a source of infection, and blood cultures did not grow a microorganism. A collateral history was taken from the patient's husband who raised concerns regarding her vaginal shelf pessary and it was therefore removed. Subsequently the patient's fever subsided, her inflammatory markers improved and she was discharged 2 days later. We believe this is the first reported case of pyrexia secondary to a non-infected vaginal pessary, and may provide clinicians with an additional line of enquiry when presented with patients with pyrexia of unknown origin.

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.

Clinical features and outcomes of patients with fever of unknown origin: a retrospective study

BACKGROUND

Few studies have reported the long-term clinical outcome of patients discharged with undiagnosed fever of unknown origin (FUO). In this study, the clinical features and outcomes of patients with unexplained fever were explored to improve our understanding of FUO.

METHOD

Patients diagnosed with FUO at admission and discharged without final diagnoses after systematic examination in the department of infectious diseases at Peking Union Medical College Hospital between 2004 and 2010 were followed up by telephone. Medical records were reviewed, and the clinical features and outcomes of patients for whom follow-up data were available were summarized.

RESULTS

Between 2004 and 2010, 58 patients with follow-up data, who were diagnosed with FUO at admission and did not have a final diagnosis at discharge, were enrolled in this study. The median duration of follow-up was 518 (0.4-830) weeks, and the fever duration was 24.6 (6.7-763.2) weeks. Final diagnoses were established in 11 cases (19%), and the diagnostic methods included clinical diagnosis, diagnostic therapy, genetic screening and biopsy pathology. The fever in 35 patients (60%) subsided during hospitalization or after discharge. Their condition was stable and self-limited after long-term follow-up, and they were ultimately thought to be cured. Two patients had periodic fever during prolonged observation: one patient needed intermittent use of nonsteroidal antiinflammatory drugs (NSAIDs), and the other needed intermittent use of NSAIDs and a steroid. Ten patients died during follow-up, with 9 deaths being caused by severe and worsening conditions related to the febrile illness.

CONCLUSIONS

Long-term follow-up should be performed for patients with undiagnosed FUO. Some patients can obtain a definitive diagnosis by repeated multiple invasive examinations and diagnostic treatment. Most patients have a self-limited illness, and their prognosis is good.

Referral of patients with fever of unknown origin to an expertise center has high diagnostic and therapeutic value

BACKGROUND

up to 50% of patients with fever of unknown origin (FUO) remain undiagnosed despite extensive evaluation. In expertise centers, at least 25-63% of these patients are referred after evaluation in another hospital. The diagnostic and therapeutic yields of referral to an expertise center are currently unknown.

AIM

To determine the diagnostic and therapeutic yield of referral of patients with fever of unknown origin (FUO) that remain undiagnosed in non-expertise hospitals.

DESIGN

Data on workup, outcome, treatment and prognosis were extracted from medical records of all 236 patients referred to the Radboud university medical center's department of internal medicine because of FUO between January 2005 and June 2014.

RESULTS

A final diagnosis could be made in 110 of 192 tertiary referred FUO patients. The rate of diagnosis did not differ between patients referred for first opinion or after tertiary referral (68.2 vs. 57.3%, P = 0.234). Over half of undiagnosed tertiary referred patients were treated, and fever resolved in half of these patients. Of 96 undiagnosed patients, two died (2.1)% and in both death was considered unrelated to the febrile disease.

CONCLUSION

The diagnostic rate in patients with FUO does not differ between patients that are tertiary referred and patients that have not been previously evaluated in another hospital. With a total diagnostic value of 57.3% and an additional therapeutic yield of 10.9% in undiagnosed patients, tertiary referral should therefore be considered in patients that remain undiagnosed in a non-expertise center.

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.

67Ga-labeled deferoxamine derivatives for imaging bacterial infection: Preparation and screening of functionalized siderophore complexes

INTRODUCTION

Deferoxamine (DFO) is a siderophore that bacteria use to scavenge iron and could serve as a targeting vector to image bacterial infection where current techniques have critical limitations. [⁶⁷Ga]-DFO, which is a mimetic of the corresponding iron complex, is taken up by bacteria in culture, however in vivo it clears too rapidly to allow for imaging of infection. In response, we developed several new DFO derivatives to identify those that accumulate in bacteria, and at sites of infection, and that could potentially have improved pharmacokinetics.

METHODS

A library of DFO derivatives was synthesized by functionalizing the terminal amine group of DFO using three different carbamate-forming reactions. Uptake of [⁶⁷Ga]-DFO and the ⁶⁷Ga-labeled derivatives by bacteria and the biodistribution of lead compounds were studied.

RESULTS

⁶⁷Ga-labeled DFO derivatives were prepared and isolated in >90% radiochemical yield and >95% radiochemical purity. The derivatives had significant but slower uptake rates in Staphylococcus aureus than [⁶⁷Ga]-DFO (6% to 60% of the control rate), with no uptake for the most lipophilic derivatives. Biodistribution studies in mice with a S. aureus infection in one thigh revealed that the ethyl carbamate derivative had an excellent infected-to-non-infected ratio (11:1), but high non-specific localization in the gall bladder, liver and small intestine.

CONCLUSIONS

The work reported shows that it is possible to functionalize DFO-type siderophores and retain active uptake of the ⁶⁷Ga-labeled complexes by bacteria. Novel ⁶⁷Ga-labeled DFO derivatives were specifically taken up by S. aureus and selected derivatives demonstrated in vivo localization at sites of infection. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: ⁶⁷Ga-labeled DFO derivatives were actively transported by bacteria using the iron-siderophore pathway, suggesting that it is possible to develop siderophore-based radiopharmaceuticals for imaging bacterial infection.

A roadmap for fever of unknown origin in children

Fever of unknown origin (FUO) in adults is conventionally defined by the occurrence of body temperatures above 38.3 degrees C (101 degrees F) for a period of 3 weeks without any identified etiology after a period of 1-week hospitalization. The issue of FUO in pediatrics is rather hazy and still represents a challenging diagnostic dilemma. Most of the available data are limited to nationwide cohorts of patients of any age. The major difficulty in establishing a diagnosis is that the characteristic features rendering specific disorders clinically recognizable are absent or subtle, hence only a painstaking questioning on family background may elicit the correct investigative path. No diagnostic algorithms are actually available and clinicians must rely on a very careful step-by-step evaluation of the single patient. The need for invasive diagnostic techniques should be closely taken into consideration when laboratory tests or simple imaging procedures fail to discern the origin of FUO. Fevers with no reasonable explanation and no localizing signs often conceal different common diseases in children, which tend to display an unusual or atypical pattern. The principal causes behind FUO in pediatric age remain infections, followed by collagen vascular diseases and neoplastic disorders, although most children with malignancies present other systemic signs or suggestive laboratory abnormalities. The possibility of autoinflammatory syndromes, drug fever, and factitious fever should also be taken into account.

Low-grade fever: how to distinguish organic from non-organic forms

BACKGROUND AND AIM

Low-grade fever (LGF) is defined as a body temperature between 37.5 and 38.3 degrees C, which is below the classical value reported for fever of unknown origin (FUO). We attempted to characterise its epidemiology, aetiology and clinical aspects to improve the methodological approach to diagnosis.

DESIGN AND METHODS

We reviewed and evaluated a survey of patients with LGF, followed as outpatients of our Department, a tertiary referral centre from 1997 to 2008. The same classifications were applied for classical FUO, and in the patients diagnosed with LGF, we also investigated for habitual hyperthermia (HH).

RESULTS

Seventy-three patients were selected and divided into two groups: group A included 32 patients classified with organic fever and group B included 41 patients with HH. Aetiology of organic LGF was: infectious disease 59%; neoplasm 3.1%; inflammatory non-infectious disease 6.2%; miscellaneous 18.7%; undiagnosed 12.5%. Mean age was significantly higher in the organic fever than in the HH group (p < 0.02). Splenomegaly and loss of weight were significantly associated with organic fever (p < 0.05), while dizziness and general malaise were associated with HH. Lack of any pathological signs at physical examination was significantly more frequent in HH (p < 0.0001). Among the biochemical tests, white blood cells and C-reactive protein were more frequently above normal limits in group A than in group B (p < 0.05).

CONCLUSIONS

In our experience, LGF requires the same methodological diagnostic approach as FUO, because there is no relationship between body temperature values and the severity of the underlying diseases, and the aetiological spectrum is also the same.

Fever of unknown origin: the role of 18F-FDG PET/CT

Fever of unknown origin (FUO) is a challenging diagnostic problem. Timely identification and precise localization of the causing process are critical for appropriate patient management. The present prospective study evaluates the role of PET/CT using (18)F-FDG in the investigation of FUO.

METHODS

A total of 48 consecutive patients (25 men, 23 women; age range, 24-82 y) with FUO underwent (18)F-FDG PET/CT scans. FUO was defined as a fever of more than 38.3 degrees C that lasted for more than 3 wk and failure to reach diagnosis after more than 1 wk of inpatient investigation. The performance of PET/CT for identifying the etiology of FUO was assessed. Final diagnosis was based on histopathology, microbiologic assays, or clinical and imaging follow-up.

RESULTS

PET/CT detected suggestive foci of increased (18)F-FDG uptake in 27 patients. In 22 of these 27 positive studies (81%), PET/CT identified the underlying disease and diagnosed infection in 9 patients, an inflammatory process in 10 patients, and malignancy in 3 patients. (18)F-FDG PET/CT was negative in 21 patients. All these patients were diagnosed as having systemic nonfocal infection or drug-induced fever or showed spontaneous resolution of the febrile state with no further evidence of a localized inflammatory, infectious, or malignant process for a clinical follow-up period of 12-36 mo.

CONCLUSION

(18)F-FDG PET/CT identified the underlying cause of the fever in 46% of the present study population and contributed to the diagnosis or exclusion of a focal pathologic etiology of the febrile state in 90% of patients. (18)F-FDG PET/CT has a high negative predictive value (100%) for assessment of FUO. If confirmed by further studies, (18)F-FDG PET/CT may be used in the future as an initial noninvasive diagnostic modality for assessment of this group of patients.