Fever of unknown origin: a systematic review of the literature for 1995???2004

Performance and value of 18F‑FDG PET/CT in patients with fever of unknown origin

Fever of unknown origin (FUO) is a common clinical and diagnostic challenge. The main aim of the present study was to evaluate the diagnostic accuracy of 18F-fluorodeoxyglucose (18FDG) positron emission tomography (PET)/CT in patients who present with FUO. Overall, 105 consecutive patients (61 men and 44 women) with a mean age of 51±35 years with FUO underwent 18FDG PET/CT scans. The performance of 18FDG PET/CT in determining the etiology of FUO was assessed. According to the PET/CT results, patients were classified into four groups: Group 1, patients with true-positive results (n=51; 49%), in whom abnormal 18FDG uptake identified the final diagnosis; group 2, patients with false-positive results (n=24; 23%), in whom 18FDG uptake was not consistent with the final diagnosis; group 3, patients with true-negative results (n=10; 9.5%), in whom the 18FDG uptake was normal and no final disease was established; and group 4, patients with false-negative results (n=20; 19%), in whom 18FDG uptake was normal and disease was finally established. Of the 51 patients with true-positive PET/CT results, 51% had infections, 35% had malignancies and 14% had inflammatory processes. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 72, 29, 68, 33 and 58%, respectively. In conclusion, the present results demonstrated that 18FDG PET/CT established the final diagnosis of FUO in the majority of patients (72%). These results support the use of 18FDG PET/CT in the initial evaluation and management of patients with FUO.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Fever of Unknown Origin

Fever of unknown origin in adolescents is a challenging disease state for which potential underlying etiology can include infectious, non-infectious inflammatory, and malignancy processes. Careful and thorough history (including exposure history), serial examination, and targeted laboratory and imaging testing is critical for these patients. In adolescents in which an etiology is discovered, infectious etiology remains the most prevalent, followed by non-infectious inflammatory diseases. In patients with non-diagnostic overall reassuring work up, the prognosis is typically self-limiting and favorable.

Microbial and Host Metabolites at the Backstage of Fever: Current Knowledge about the Co-Ordinate Action of Receptors and Molecules Underlying Pathophysiology and Clinical Implications

Fever represents an elevation of body temperature, that exerts a protective effect against pathogens. Innate immune cells and neurons are implicated in the regulation of body temperature. Pathogen-associated molecular patterns, i.e., lipopolysaccharides from Gram-negative bacteria and peptidoglycan and lipoteichoic acid from Gram-positive bacteria are exogenous pyrogens, that bind to Toll-like receptors on immune and non-immune cells. The subsequent release of pro-inflammatory cytokines [interleukin-1 (IL-1), IL-6 and Tumor necrosis factor-alpha] and their passage through the brain trigger the febrile response. In fact, neurons of the pre-optic area produce prostaglandin E2 (PGE2), that, in turn, bind to the PGE2 receptors; thus, generating fever. Apart from classical non-steroidal anti-inflammatory drugs, i.e., aspirin and acetaminophen, various botanicals are currently used as antipyretic agents and, therefore, their mechanisms of action will be elucidated.

Use of Quantitative Metagenomics Next-Generation Sequencing to Confirm Fever of Unknown Origin and Infectious Disease

A body temperature >38.3°C that lasts ≥3 weeks and lacks a clear diagnosis after 1 week of standard hospital examination and treatment is called "fever of unknown origin" (FUO). The main causes of FUO are infections, hematological diseases, autoimmune diseases, and other non-infectious inflammatory diseases. In recent years, quantitative metagenomics next-generation sequencing (Q-mNGS) has been used widely to detect pathogenic microorganisms, especially in the contribution of rare or new (e.g., severe acute respiratory syndrome-coronavirus-2) pathogens. This review addresses the undetermined cause of fever and its evaluation by Q-mNGS.

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

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

Fever of unknown origin (FUO) on a land on cross-roads between Asia and Europa; a multicentre study from Turkey

AIMS

The differential diagnosis of Fever of Unknown Origin (FUO) is still a major clinical challenge despite the advances in diagnostic procedures. In this multicentre study, we aimed to reveal FUO aetiology and factors influencing the final diagnosis of FUO in Turkey.

METHODS

A total of 214 patients with FUO between the years 2015 and 2019 from 13 tertiary training and research hospitals were retrospectively evaluated.

RESULTS

The etiologic distribution of FUO was infections (44.9%), malignancies (15.42%), autoimmune/inflammatory (11.68%) diseases, miscellaneous diseases (8.41%) and undiagnosed cases (19.62%). Brucellosis (10.25%), extrapulmonary tuberculosis (6.54%) and infective endocarditis (6.54%) were the most frequent three infective causes. Solid malignancies (7.1%) and lymphoma (5.6%), adult-onset still's disease (6.07%) and thyroiditis (5.14%) were other frequent diseases. The aetiological spectrum did not differ in elderly people (P < .05). Infections were less frequent in Western (34.62%) compared with Eastern regions of Turkey (60.71%) (P < .001, OR: 0.31, 95% Cl: 0.19 to 0.60). The ratio of undiagnosed aetiology was significantly higher in elderly people (p: 0.046, OR: 2.34, 95% Cl: 1.00 to 5.48) and significantly lower in Western Turkey (P: .004, OR: 3.07, 95% Cl: 1.39 to 6.71).

CONCLUSIONS

Brucellosis, extrapulmonary tuberculosis and infective endocarditis remain to be the most frequent infective causes of FUO in Turkey. Solid tumours and lymphomas, AOSD and thyroiditis are the other common diseases. The aetiological spectrum did not differ in elderly people, on the other hand, infections were more common in Eastern Turkey. A considerable amount of aetiology remained undiagnosed despite the state-of-the-art technology in healthcare services.

Current Applications for Nuclear Medicine Imaging in Pulmonary Disease

Purpose of Review

The main goal of the article is to familiarize the reader with commonly and uncommonly used nuclear medicine procedures that can significantly contribute to improved patient care. The article presents examples of specific modality utilization in the chest including assessment of lung ventilation and perfusion, imaging options for broad range of infectious and inflammatory processes, and selected aspects of oncologic imaging. In addition, rapidly developing new techniques utilizing molecular imaging are discussed.

Recent Findings

The article describes nuclear medicine imaging modalities including gamma camera, SPECT, PET, and hybrid imaging (SPECT/CT, PET/CT, and PET/MR) in the context of established and emerging clinical applications. Areas of potential future development in nuclear medicine are discussed with emphasis on molecular imaging and implementation of new targeted tracers used in diagnostics and therapeutics (theranostics).

Summary

Nuclear medicine and molecular imaging provide many unique and novel options for the diagnosis and treatment of pulmonary diseases. This article reviews current applications for nuclear medicine and molecular imaging and selected future applications for radiopharmaceuticals and targeted molecular imaging techniques.

Fever of unknown origin (FUO): which are the factors influencing the final diagnosis? A 2005-2015 systematic review

BACKGROUND

The differential diagnosis of Fever of Unknown Origin (FUO) is very extensive, and includes infectious diseases (ID), neoplasms and noninfectious inflammatory diseases (NIID). Many FUO remain undiagnosed. Factors influencing the final diagnosis of FUO are unclear.

METHODS

To identify factors associated with FUO diagnostic categories, we performed a systematic review of classical FUO case-series published in 2005-2015 and including patients from 2000. Moreover, to explore changing over time, we compared these case-series with those published in 1995-2004.

RESULTS

Eighteen case-series, including 3164 patients, were included. ID were diagnosed in 37.8% of patients, NIID in 20.9%, and neoplasm in 11.6%, FUO were undiagnosed in 23.2%. NIIDs significantly increased over time. An association exists between study country income level and ID (increasing when the income decreases) and undiagnosed FUO (increasing when the income increases); even if not significant, the use of a pre-defined Minimal Diagnostic Work-up to qualify a fever as FUO seems to correlate with a lower prevalence of infections and a higher prevalence of undiagnosed FUO. The multivariate regression analysis shows significant association between geographic area, with ID being more frequent in Asia and Europe having the higher prevalence of undiagnosed FUO. Significant associations were found with model of study and FUO defining criteria, also.

CONCLUSIONS

Despite advances in diagnostics, FUO still remains a challenge, with ID still representing the first cause. The main factors influencing the diagnostic categories are the income and the geographic position of the study country.

Seroepidemiological and molecular investigations of infections with Crimean-Congo haemorrhagic fever virus in Kazakhstan

OBJECTIVES

The aim of this study was to detect the seroprevalence of Crimean-Congo haemorrhagic fever virus (CCHFV) in patients with fever of unknown origin (FUO) in endemic (Kyzylorda) and non-endemic (Almaty) oblasts of Kazakhstan.

METHODS

Paired serum samples from 802 patients with FUO were collected. Serum samples were investigated by ELISA to detect IgG and IgM antibodies against CCHFV. Sera with suspected acute infection were further investigated by RT-PCR to detect the viral RNA.

RESULTS

IgG antibodies were detected in 12.7% of the sera from both oblasts. Acute infection was shown by IgM ELISA in four patients from Kyzylorda, with only one developing severe CCHF. Viral RNA was found by RT-PCR in the other three patients' sera. Phylogenetic analysis of partial L and S segments revealed CCHFV genotype Asia 2 and a possible reassortment between the genotypes Asia 1/Asia 2. Animal husbandry, such as working with cattle and horses, was significantly associated with CCHFV seropositivity.

CONCLUSIONS

The antibodies and viral RNA detected in sera indicate that mild or even asymptomatic CCHFV infections are presented in Kazakhstan. This study describes the circulation of CCHFV in the so far non-endemic Almaty oblast for the first time. In conclusion, physicians treating patients with FUO in Kazakhstan should be aware of mild CCHF.

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.

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.

Pyrexia of unknown origin in clinical practice

This article revisits concepts of pyrexia of unknown origin to reflect current clinical practice. It describes the evolution of the term, in line with the changing spectrum and pace of investigations, and introduces key questions that may be used to evaluate a pyrexia of unknown origin.

Fever of Unknown Origin in Childhood

Childhood fever of unknown origin (FUO) is most often related to an underlying infection but can also be associated with a variety of neoplastic, rheumatologic, and inflammatory conditions. Repeated, focused reviews of patient history and physical examination are often helpful in suggesting a likely diagnosis. Diagnostic workup should be staged, usually leaving invasive testing for last. Advances in molecular genetic techniques have increased the importance of these assays in the diagnosis of FUO in children.

Limited diagnostic value of procalcitonin in early diagnosis of adult onset Still's disease

A 17-year-old female patient was referred to the Infectious Diseases Ward because of fever lasting for 14 days. On admission to the hospital the patient was in a generally good state, without any abnormalities on physical examination. Laboratory investigation revealed elevated inflammatory markers. Diagnostic imaging comprising chest X-ray, abdominal ultrasonography, and echocardiography showed no abnormalities. During the hospitalization, there occurred episodes of fever with skin rash and musculoskeletal pain of the lower limbs. Procalcitonin concentrations continued to increase. C-reactive protein concentrations decreased during therapy, starting from 191 mg/l. On the 23^rd day of the disease, edema of the feet, ankles, and knees appeared. On the basis of the clinical picture and after excluding other possible causes of fever, the patient was diagnosed with adult onset Still's disease. The procalcitonin concentration was normalized after 5 days of steroid therapy. The patient was discharged under ambulatory rheumatologic supervision.

Febrile syndrome of unknown origin: Indications for 18F-FDG PET/CT in inflammatory and infectious processes

Fever of unknown origin is defined as a body temperature greater than 38.3°C lasting more than three weeks for which the cause could not be found within one week of hospital admission. More than 200 causes have been reported, and these can be classified into four categories: infections, inflammatory diseases, oncologic processes, and miscellaneous conditions. Noninvasive diagnostic techniques are used in 69.2% of cases and invasive techniques in 30.8%. Structural imaging techniques show the morphological changes from infectious, inflammatory, and tumor-related processes, but they do not allow the detection of the early changes brought about by these processes. The metabolic information provided by ¹⁸F-FDG PET/CT has a promising role in these patients. ¹⁸F-FDG uptake is based on the cells' use of glucose as a source of energy, so it can be observed in infectious, inflammatory, and tumor-related processes. The established non-oncologic indications for ¹⁸F-FDG PET/CT are sarcoidosis, osteomyelitis, spondylodiscitis, fever of unknown origin, and vasculitis, which together account for more than 85% of studies.

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.

[18F]FDG-PET/CT for the diagnosis of patients with fever of unknown origin

BACKGROUND AND AIMS

The diagnosis of patients with fever of unknown origin (FUO) remains a challenging medical problem. We aimed to assess the diagnostic contribution of 18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET)/computed tomography (CT) for the evaluation of FUO.

METHODS

We performed a 4-year retrospective single-center study of all hospitalized patients that underwent FDG-PET/CT for evaluation of FUO. The final diagnosis of the febrile disease was based on clinical, microbiological, radiological and pathological data available at the final follow-up. Predictors for a contributory exam were sought.

RESULTS

One hundred and twelve patients underwent FDG-PET/CT for the investigation of FUO in the years 2008-2012 and were included in the study. A final diagnosis was determined in 83 patients (74%) and included: infectious disease in 49 patients (43%), non-infectious inflammatory disease in 17 patients (16%), malignancies in 15 patients (14%), other diagnoses in 2 patients (1.7%), FUO resolved with no diagnosis and no evidence of disease during a 6-month follow-up in 23 patients (20%), and death with fever and with no diagnosis in 6 patients (5%). Seventy-four FDG-PET/CT studies (66%) were considered clinically helpful and contributory to diagnosis (46% positive contributory value and 20.5% contributory to exclusion of diagnosis). PET/CT had a sensitivity of 72.2%, a specificity of 57.5%, a positive predictive value (PPV) of 74.2% and a negative predictive value (NPV) of 53.5%. On multivariable analysis, significant predictors of a positive PET/CT contributory to diagnosis were a short duration of fever and male gender.

CONCLUSIONS

PET/CT is an important diagnostic tool for patients with FUO.

Sepsis in head and neck cancer patients treated with chemotherapy and radiation: Literature review and consensus

The reporting of infection/sepsis in chemo/radiation-treated head and neck cancer patients is sparse and the problem is underestimated. A multidisciplinary group of head and neck cancer specialists from Italy met with the aim of reaching a consensus on a clinical definition and management of infections and sepsis. The Delphi appropriateness method was used for this consensus. External expert reviewers then evaluated the conclusions carefully according to their area of expertise. The paper contains seven clusters of statements about the clinical definition and management of infections and sepsis in head and neck cancer patients, which had a consensus. Furthermore, it offers a review of recent literature in these topics.

The diagnostic role of 18-fluorodeoxyglucocose-positron emission tomography/computed tomography in occult bacteremia searching underlying primary disease

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 (Fever of unknown origin). However, till today, there are limited studies about the role of FDG PET or PET/CT in evaluation of FUO. Conventional diagnostic methods are still not adequate to reveal underlying reason in approximately 50% of patients with FUO especially in cases presenting with diagnostic challenges i.e. involvement of two or more organ systems with seemingly no correlation. We report a case of two years old Indian female child who presented with fever of one month duration, CT and MRI reported nonspecific findings. She underwent Whole body 18 FDG PET/CT for further evaluation, which revealed FDG avid rim lesion with central photopenic defect suspicious of pyogenic abscess in high parietal cortex along with bilateral lung nodules. This confirmed the diagnosis of a brain abscess secondary to pulmonary infection. We emphasize the utility of 18 FDG PET/CT as imaging modality, highlight the diagnostic difficulties using current serological and radiological measures, and propose managing FUO with 18 FDG PET/CT in cases empirically prior to more invasive measures.

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.

Spectrum of 18F-FDG PET/CT findings in patients presenting with fever of unknown origin

OBJECTIVE

The objective of this article is to provide an illustrative tutorial highlighting the clinical utility of (18)F-FDG PET/CT for imaging patients presenting with fever of unknown origin (FUO).

CONCLUSION

FDG PET/CT is a powerful tool in localizing an inciting source in patients with FUO. The high sensitivity of FDG PET/CT for diagnosing infective, inflammatory, and neoplastic processes can be exploited in this setting because these processes are often the common causes of FUO.

The role of 18F-FDG PET or PET/CT in the detection of fever of unknown origin

Even with the recent advance in diagnostic tools and techniques, fever of unknown origin (FUO) remains a clinical challenge. A wide range of diseases, mainly infections, autoimmune conditions (inflammatory diseases), malignancies and miscellaneous can cause FUO. Positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) scanning makes a great contribution to the diagnosis and differential diagnosis of FUO due to the high sensitivity of pathological accumulation of 18F-FDG. The diagnostic yield of PET/CT is higher than traditional radiographic imaging and other nuclear medicine scanning. Owing to the numerous advantages of PET/CT including high sensitivity and the ability to perform whole-body scans, many rare diseases presenting with FUO can be detected and the spectrum of diseases that can exhibit FUO has been increasing. Recent studies utilizing FUO are discussed in this paper. However, there are limited data available about the role of 18F-FDG PET or PET/CT in evaluation of FUO.

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.

An unusual case of DRESS syndrome

BACKGROUND

DRESS syndrome (drug reaction with eosinophilia and systemic symptoms) is a rare but severe drug reaction.

OBSERVATIONS

A 27-year-old male with paranoid schizophrenia was hospitalized with all three diagnostic criteria of DRESS syndrome: cutaneous drug eruption, hematological abnormalities (presence of atypical lymphocytes on blood smear) and systemic involvement (generalized lymphadenopathy and hepatitis). On hospitalization the patient exhibited an unusual fever pattern of high temperatures in the morning hours and lower temperatures towards evening. In this case of a patient who needs life-long therapy, we demonstrated the value of the IFN-gamma release test, which showed positive reactivity to 3 out of 9 suspicious drugs: paracetamol, phenytoin and dypirone, allowing for more therapeutic options. After therapy, at 6-month follow-up the patient is doing well under haloperidol treatment, laboratory values including liver function tests are normal and his skin condition is good.

CONCLUSION

We suggest that clinicians take the fever pattern of high temperatures in the morning hours and lower temperatures towards evening into account in a patient presenting with a severe cutaneous drug eruption. An interferone-gamma release test may facilitate identification of drugs responsible for the drug reaction.

[Prolonged fever: specific issues in the young adult population]

Early studies on prolonged fever date back to the 1960s. Fifty years later, prolonged unexplained fever remains a diagnostic challenge to the general internists. Although the aetiologies of prolonged fevers have not changed much in the general population, the distribution between the various causes is not the same anymore. A regular decrease in infectious and neoplastic causes is noticed whatever the age. Prolonged fevers related to inflammatory disorders and fevers that remain of unknown origin still represent approximately 30 to 50% of the cases. In the young adult population, as in the older patients, prolonged fevers can be attributed to four groups: infection, inflammation, neoplasic and other aetiologies (including drug-related fevers). In the young adult population, the management of prolonged fever presents some specific issues that are the purpose of this review coupled with our own experience. The prognosis of undiagnosed prolonged fever is usually favourable, as a life-threatening aetiology is exceptionally diagnosed during the follow-up if the initial management was complete and accurate.

C-reactive protein in critically ill cancer patients with sepsis: influence of neutropenia

INTRODUCTION

Several biomarkers have been studied in febrile neutropenia. Our aim was to assess C-reactive protein (CRP) concentration in septic critically ill cancer patients and to compare those with and without neutropenia.

METHODS

A secondary analysis of a matched case-control study conducted at an oncologic medical-surgical intensive care unit (ICU) was performed, segregating patients with severe sepsis/septic shock. The impact of neutropenia on CRP concentrations at admission and during the first week of ICU stay was assessed.

RESULTS

A total of 154 critically ill septic cancer patients, 86 with neutropenia and 68 without, were included in the present study. At ICU admission, the CRP concentration of neutropenic patients was significantly higher than in non-neutropenic patients, 25.9 ± 11.2 mg/dL vs. 19.7 ± 11.4 mg/dL (P = 0.009). Among neutropenic patients, CRP concentrations at ICU admission were not influenced by the severity of neutropenia (< 100/mm3 vs. ≥ 100/mm3 neutrophils), 25.1 ± 11.6 mg/dL vs. 26.9 ± 10.9 mg/dL (P = 0.527). Time dependent analysis of CRP from Day 1 to Day 7 of antibiotic therapy showed an almost parallel decrease in both groups (P = 0.335), though CRP of neutropenic patients was, on average, always higher in comparison to that of non-neutropenic patients.

CONCLUSIONS

In septic critically ill cancer patients CRP concentrations are more elevated in those with neutropenia. However, the CRP course seems to be independent from the presence or absence of neutropenia.

Prevalence of connective tissue diseases in egyptian patients presenting with Fever of unknown origin

OBJECTIVE

To estimate the prevalence of connective tissue diseases in patients presenting with fever of unknown origin (FUO).

PATIENTS AND METHODS

In this study thirty patients diagnosed as FUO (Group 1), in 2008, were included in an observational study and diagnostic workup. Additionally, retrospective analysis of seventy patients' files (Group 2), for patients who presented with prolonged unexplained pyrexia to the same hospital in the previous two years, was performed. Patients were subjected to: full clinical assessment including full history taking, thorough clinical examination, laboratory investigations including the basic investigations for patients with prolonged fever, complete blood count, erythrocytes sedimentation rate, urine analysis and culture, blood culture, sputum culture and plain chest X ray. Further diagnostic work up and/or procedures were requested according to the potential diagnostic clues (PDC) present in every patient.

RESULTS

Out of 100 FUO patients, 50% were found to have infectious diseases, 24% were found to have connective tissue diseases, 8% miscellaneous causes and 7% neoplastic diseases (P < 0.05). In 11 patients no definite cause for FUO could be identified. Connective tissue patients were: eight systemic lupus patients (33.3%), five patients with familial mediterranean fever (20.8%), four patients with rheumatoid arthritis (16.6%), three patients (12.5%) with Still's disease and Rheumatic fever and one patient with Behçet syndrome/Crohn's disease (4.3%), (P < 0.05).

CONCLUSIONS

Despite the advanced technology, FUO remains a challenging medical problem. Infections were the most common cause of FUO in Egypt, confirming the trends found in other parts of the world. There was an increased prevalence of connective tissue patients presented with prolonged unexplained fever. A keen clinical eye, meticulous history taking and repeated physical examination remained the most important diagnostic tools in FUO patients.

The Diagnostic Role of FDG PET/CT in Patients with Fever of Unknown Origin

Objective: Fever of unknown origin (FUO) is a challenge for the physician and needs use of clinical, laboratory, and imaging studies and also invasive and/or non-invasive interventions to detect the etiology. The aim of present study was to assess the role of FDG PET/CT in determining the etiology in patients with FUO.

Material and Methods: Twenty-four patients (median age 52, range 5-77 years, 6 female, 18 male) who were diagnosed with FUO were retrospectively analyzed in this study. Before the FDG PET/CT studies, none of them had a definitive reason for their diseases investigated by conventional radiological or scintigraphic methods, clinical and laboratory observations.

Results: The positive result was achieved in 19 (79.2%) of 24 patients as findings of the FDG PET/CT. However, FDG PET/CT was useful for definitive diagnosis in 12 (63.2%) of 19 positive patients. Malignant diseases were determined to be the underlying cause of FUO in 5 (41.6%) of 12 patients. Noninfectious inflammatory causes were detected in 2 (16.7%) patients, infections were exhibited in 3 (25%) patients, and miscellaneous diseases demonstrated in 2 (16.7%) patients. In 7 patients the detected pathological uptakes on FDG PET/CT were not helpful for the definitive diagnosis. In remaining 5 patients who showed no pathological uptake in the FDG PET/CT, diagnosis could not be established by other methods, as well. The sensitivity, specificity, and positive and negative predictive values for the determination of FUO etiology were 92.3%, 45.4%, 63.1%, and 100% for FDG PET/CT.

Conclusion: Our results demonstrate that FDG PET/CT seems to have considerable contribution to reveal the reason of undiagnosed patients with FUO investigated by conventional diagnostic methods, clinical and laboratory observations.

Conflict of interest:None declared.

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.

Procalcitonin as a marker for the detection of bacteremia and sepsis in the emergency department

Rapid diagnosis of bloodstream infections (BSIs) in the emergency department (ED) is challenging, with turnaround times exceeding the timeline for rapid diagnosis. We studied the usefulness of procalcitonin as a marker of BSI in 367 adults admitted to our ED with symptoms of systemic infection. Serum samples obtained at the same time as blood cultures were available from 295 patients. Procalcitonin levels were compared with blood culture results and other clinical data obtained during the ED visit. Procalcitonin levels of less than 0.1 ng/mL were considered negative; all other levels were considered positive. In 16 patients, there was evidence of BSI by blood culture, and 12 (75%) of 16 patients had a procalcitonin level of more than 0.1 ng/mL. In 186 (63.1%) of 295 samples, procalcitonin values were less than 0.1 ng/mL, and all were culture negative. With a calculated threshold of 0.1475 ng/mL for procalcitonin, sensitivity and specificity for the procalcitonin assay were 75% and 79%, respectively. The positive predictive value was 17% and the negative predictive value 98% compared with blood cultures. Procalcitonin is a useful marker to rule out sepsis and systemic inflammation in the ED.

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.

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.

Inflammation of unknown origin versus fever of unknown origin: two of a kind

OBJECTIVES

A vast literature exists on fever of unknown origin (FUO), characterized by prolonged and perplexing fevers >38.3 degrees C. In contrast, no studies are available to guide the approach to inflammation of unknown origin (IUO), defined as prolonged and perplexing inflammation with temperatures <38.3 degrees C. We aimed to determine the diagnostic yield, the case-mix, and the outcome of patients with IUO, relative to patients with FUO.

METHODS

We matched 57 patients with IUO to 57 patients with FUO of the same gender (54% male) and a similar age (median: 67 years).

RESULTS

A diagnosis was established in 35 patients with IUO (61%) and in 33 patients with FUO (58%) (p=.70). The case-mix did not differ significantly (p=.43). Non-infectious inflammatory disorders were the dominant diagnostic category in the IUO group (16 patients), while in the FUO group, similar numbers of malignancies [10], infections [9], and non-infectious inflammatory diseases [9] were diagnosed. (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scan contributed comparably to the diagnosis in both groups (in 18 of 50, 36%, patients with IUO and in 13 of 40, 33%, patients with FUO) (p=.83). In both groups, 7 patients (12%) died during an average follow-up of 1 year.

CONCLUSION

Diagnostic yield, case-mix, contribution of FDG-PET scan and vital outcome were similar in patients with IUO and FUO. These data suggest that the 38.3 degrees C boundary may be arbitrary and that the diagnostic approaches used in FUO can be applied to IUO.

S100A12 is a novel molecular marker differentiating systemic-onset juvenile idiopathic arthritis from other causes of fever of unknown origin

OBJECTIVE

Fever of unknown origin (FUO) in children presents a diagnostic challenge. The differential diagnosis includes systemic-onset juvenile idiopathic arthritis (JIA), an autoinflammatory syndrome associated with activation of phagocytic cells that, at presentation, is difficult to differentiate from severe systemic infections. The aim of this study was to investigate whether serum concentrations of the phagocytic proinflammatory protein S100A12 may help in deciding whether to treat patients with FUO with antibiotics or immunosuppressive agents.

METHODS

Serum samples were obtained from 45 healthy control subjects and from 240 patients (60 with systemic-onset JIA, 17 with familial Mediterranean fever [FMF], 18 with neonatal-onset multisystem inflammatory disease [NOMID], 17 with Muckle-Wells syndrome [MWS], 40 with acute lymphoblastic leukemia [ALL], 5 with acute myeloblastic leukemia [AML], and 83 with systemic infections). All samples were collected at the time of presentation, before the initiation of any treatment, and concentrations of S100A12 were determined by enzyme-linked immunosorbent assay.

RESULTS

The mean +/- 95% confidence interval serum levels of S100A12 were as follows: in patients with JIA, 7,190 +/- 2,690 ng/ml; in patients with FMF, 6,720 +/- 4,960 ng/ml; in patients with NOMID, 720 +/- 450 ng/ml; in patients with MWS, 150 +/- 60 ng/ml; in patients with infections, 470 +/- 160 ng/ml; in patients with ALL, 130 +/- 80 ng/ml; in patients with AML, 45 +/- 60 ng/ml; in healthy control subjects, 50 +/- 10 ng/ml. The sensitivity and specificity of S100A12 to distinguish between systemic-onset JIA and infections were 66% and 94%, respectively.

CONCLUSION

S100A12, a marker of granulocyte activation, is highly overexpressed in patients with systemic-onset JIA or FMF, which may point to as-yet unknown common inflammatory mechanisms in these diseases. The measurement of S100A12 serum levels may provide a valuable diagnostic tool in the evaluation of FUO.

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.