Fever of Unknown Origin: An Evidence-Based Review

Neutrophil-to-ferritin ratio can predict hematological causes of fever of unknown origin

Despite advancements in diagnostic modalities, delineating the etiology of fever of unknown origin (FUO) remains a significant challenge for clinicians. Notably, cases with hematological malignancies often have a poor prognosis due to delayed diagnosis. This study investigated the potential of readily obtainable laboratory markers to differentiate hematological causes from other etiologies during the early stages of FUO. A retrospective analysis was conducted on the medical records of 100 patients who fulfilled the modified FUO criteria between January 2010 and April 2023. Hematological etiologies were identified in 26 of the 100 patients. Peripheral blood neutrophil, lymphocyte, platelet counts, and the systemic immune inflammation (SII) index, were significantly lower in the hematological group compared to the non-hematological group. Conversely, serum ferritin levels were demonstrably higher in the hematological group. ROC analysis identified a neutrophil-to-ferritin ratio (NFR) cutoff value of < 8.53 as optimal for predicting hematological etiology. Subsequent multivariate analysis demonstrated that the NFR was the sole independent predictor of hematological etiology (p = 0.013).This study proposes a novel approach for early diagnosis of a potentially life-threatening subset of FUO patients. The NFR presents as an inexpensive and readily available marker for predicting hematological etiology in FUO cases.

Infectious causes of fever of unknown origin in developing countries: An international ID-IRI study

Background

Fever of unknown origin (FUO) in developing countries is an important dilemma and further research is needed to elucidate the infectious causes of FUO.

Methods

A multi-center study for infectious causes of FUO in lower middle-income countries (LMIC) and low-income countries (LIC) was conducted between January 1, 2018 and January 1, 2023. In total, 15 participating centers from seven different countries provided the data, which were collected through the Infectious Diseases-International Research Initiative platform. Only adult patients with confirmed infection as the cause of FUO were included in the study. The severity parameters were quick Sequential Organ Failure Assessment (qSOFA) ≥2, intensive care unit (ICU) admission, vasopressor use, and invasive mechanical ventilation (IMV).

Results

A total of 160 patients with infectious FUO were included in the study. Overall, 148 (92.5%) patients had community-acquired infections and 12 (7.5%) had hospital-acquired infections. The most common infectious syndromes were tuberculosis (TB) (n=27, 16.9%), infective endocarditis (n=25, 15.6%), malaria (n=21, 13.1%), brucellosis (n=15, 9.4%), and typhoid fever (n=9, 5.6%). Plasmodium falciparum, Mycobacterium tuberculosis, Brucellae, Staphylococcus aureus, Salmonella typhi, and Rickettsiae were the leading infectious agents in this study. A total of 56 (35.0%) cases had invasive procedures for diagnosis. The mean qSOFA score was 0.76±0.94 {median (interquartile range [IQR]): 0 (0-1)}. ICU admission (n=26, 16.2%), vasopressor use (n=14, 8.8%), and IMV (n=10, 6.3%) were not rare. Overall, 38 (23.8%) patients had at least one of the severity parameters. The mortality rate was 15 (9.4%), and the mortality was attributable to the infection causing FUO in 12 (7.5%) patients.

Conclusions

In LMIC and LIC, tuberculosis and cardiac infections were the most severe and the leading infections causing FUO.

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

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

Fever of Unknown Origin: The Workup and Diagnosis of Pel-Ebstein Fever

The clinical and diagnostic workup of fever of unknown origin (FUO) is key in the treatment of patients on the internal medicine service. In this article, the authors present a case of fever of unknown origin, walk through the differential diagnosis, explain the laboratory testing ordered in the workup of the patient as well as the resulting values of said testing, and discuss the pathophysiology and diagnostic criteria for the diagnosis of Pel-Ebstein fever. The authors also discuss a clinical pearl when working with electronic health records to ensure that the needs of the patient in question are met.

Application of Machine Learning for the Prediction of Etiological Types of Classic Fever of Unknown Origin

Background: The etiology of fever of unknown origin (FUO) is complex and remains a major challenge for clinicians. This study aims to investigate the distribution of the etiology of classic FUO and the differences in clinical indicators in patients with different etiologies of classic FUO and to establish a machine learning (ML) model based on clinical data. Methods: The clinical data and final diagnosis results of 527 patients with classic FUO admitted to 7 medical institutions in Chongqing from January 2012 to August 2021 and who met the classic FUO diagnostic criteria were collected. Three hundred seventy-three patients with final diagnosis were divided into 4 groups according to 4 different etiological types of classical FUO, and statistical analysis was carried out to screen out the indicators with statistical differences under different etiological types. On the basis of these indicators, five kinds of ML models, i.e., random forest (RF), support vector machine (SVM), Light Gradient Boosting Machine (LightGBM), artificial neural network (ANN), and naive Bayes (NB) models, were used to evaluate all datasets using 5-fold cross-validation, and the performance of the models were evaluated using micro-F1 scores. Results: The 373 patients were divided into the infectious disease group (n = 277), non-infectious inflammatory disease group (n = 51), neoplastic disease group (n = 31), and other diseases group (n = 14) according to 4 different etiological types. Another 154 patients were classified as undetermined group because the cause of fever was still unclear at discharge. There were significant differences in gender, age, and 18 other indicators among the four groups of patients with classic FUO with different etiological types (P < 0.05). The micro-F1 score for LightGBM was 75.8%, which was higher than that for the other four ML models, and the LightGBM prediction model had the best performance. Conclusions: Infectious diseases are still the main etiological type of classic FUO. Based on 18 statistically significant clinical indicators such as gender and age, we constructed and evaluated five ML models. LightGBM model has a good effect on predicting the etiological type of classic FUO, which will play a good auxiliary decision-making function.

Usefulness of 18FDG-PET/CT and MRI in an immunocompetent patient with fever of unknown origin and following diagnosis of skeletal tuberculosis

INTRODUCTION

Fever of unknown origin (FUO) is one of the most difficult diagnostic dilemmas in current medicine. The main causes of FUO in developed countries are non-infectious inflammatory diseases, while infections are predominant in developing countries. Among infections, Mycobacterium Tuberculosis (TB) is the most frequent cause and it can involve multiple tissues and organs.

CASE AND OUTCOMES

We report a case of FUO in an immunocompetent patient with fever of unknown origin, finally diagnosed with skeletal TB thanks to a multidisciplinary approach, using FDG-PET/CT, MRI, and biopsy. PET/CT findings were non-specific (infection or inflammation versus malignancy); therefore, hip Magnetic Resonance Imaging (MRI) was performed and infection was suspected on basis of MRI findings, so a bone biopsy was then performed and skeletal TB was diagnosed.

DISCUSSION

A successful diagnostic workup of FUO has to take into account detailed medical history, physical examination, laboratory tests, blood and urine cultures, and standard imaging (Ultrasonography, CT, or MRI). However, this combination of clinical evaluation, standardized laboratory tests and simple imaging procedures often do not lead to a definite diagnosis; ⁸F-FDG-PET-CT could be performed to help in diagnosis and also to guide additional diagnostic tests such as MRI and biopsy.

CONCLUSION

This case demonstrates the importance of the integration of different imaging modalities, in particular, MRI and FDG-PET/CT in patients with FUO. Skeletal TB should always be included in the diagnostic hypothesis of FUO, even in immunocompetent patients of non-endemic countries.

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.

111In-Labeled White Blood Cell Uptake in the Urinary Bladder in Occult Urinary Tract Infection

ABSTRACT

A 55-year-old woman with multiple medical problems, including anuric, dialysis-dependent, end-stage renal disease, presented with persistent fever of unknown origin. Despite extensive workup with cross-sectional imaging and panculture, the etiology was not found. Eventually, an 111In-labeled WBC scan was performed to evaluate for occult infection, which revealed intense heterogeneous uptake in the urinary bladder. Subsequent bladder catheterization showed pus and blood, which grew Klebsiella pneumoniae. The fevers resolved with adjustment of the therapy. Although urinary analysis and culture are standard practice in the workup of fever of unknown origin, anuria may obscure this common source of infection.

Gallium citrate-67 single-photon emission computed tomography/computed tomography for localizing the foci of classic fever and inflammation of unknown origin: A retrospective study of diagnostic yield

OBJECTIVES

Only few studies have assessed the use of gallium citrate-67 single-photon emission computed tomography/computed tomography (67Ga-SPECT/CT) for localizing the foci of classic fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Hence, the current study aimed to assess the diagnostic contribution of 67Ga-SPECT/CT in a tertiary referral setting where nuclear imaging tests are performed after an unsuccessful comprehensive primary diagnostic workup.

METHODS

We retrospectively assessed the medical records of 27 adult patients with FUO/IUO who had an unsuccessful diagnostic workup and who underwent 67Ga-SPECT/CT for the localization of FUO/IUO foci in our university hospital between 2013 and 2019. The primary outcome was diagnostic yield. The secondary outcomes were overall clinical efficacy and spontaneous remission of FUO/IUO symptoms in patients with a negative 67Ga-SPECT/CT finding.

RESULTS

Almost all patients completed the recommended diagnostic workup, except for urine culture and abdominal ultrasonography. Moreover, prior to 67Ga-SPECT/CT, all patients underwent thoraco-abdominopelvic CT scan, which was a non-diagnostic procedure. After a median follow-up of 843 days, the cause was identified in 16 (59%) patients. 67Ga-SPECT/CT successfully localized the FUO/IUO foci in eight patients (diagnostic yield = 30%; 95% confidence interval [CI]: 14%-50%). However, the causes remained unknown during follow-up in 11 (41%) patients. Among them, five experienced spontaneous regression of symptoms. 67Ga-SPECT/CT was negative in four of the five patients with spontaneous regression in symptoms without a definite cause. Considering this an important event, the overall clinical efficacy of 67Ga-SPECT/CT increased to 44% (95% CI: 25%-65%).

CONCLUSION

67Ga-SPECT/CT had an acceptable diagnostic yield for the localization of FUO/IUO foci, which are challenging to diagnose, in a contemporary tertiary referral care setting. In patients who experienced spontaneous regression in symptoms with an unexplained cause, the absence of abnormal uptake might indicate prospective spontaneous remission. Thus, 67Ga-SPECT/CT could be an active first-line nuclear imaging modality in settings where fluorine-18-fluorodeoxy glucose positron emission tomography and computed tomography is not available for the assessment of FUO/IUO causes.

Hospital based serological evidence of rickettsial diseases and assessment diagnostic tests of pyrexia of unknown origin

The present study examined hospital-based serological tests of rickettsial infections and assessment for diagnosis of pyrexia of unknown origin (PUO). Blood samples were tested for Weil Felix antigens, ELISA for scrub typhus group and polymerase chain reaction (PCR) to detect the presence of DNA of spotted and scrub typhus group with the help of specific oligonucleotide. We tested 450 patient samples and found 101 Weil Felix-positive with 15 having ≥320 titres. IgM ELISA identified 32 (7.1%) positive cases. Positive PCR was seen in 13 (2.9%) samples, being only 40.1% of those testing positive for ELISA. Rickettsial infection is predominantly diagnosed through serological evidence in combination with molecular techniques. The Weil Felix test has a number of disadvantages and tends to provide false-positive results in a number of scenarios, especially where scrub typhus and spotted fever are widely distributed.

A case of fever of unknown origin and recurrent hospital admissions in a cardiac patient: emergence of Enterobacter cloacae

A 72-year-old gentleman with significant cardiac history and a pacemaker in situ initially presented to the emergency department 5 days after he had his pacemaker-unit batteries changed. He had deranged vital signs, productive cough and fever. His chest plain radiograph did not show evidence of infection; however, he had right basal crackles on auscultation, which suggested a lower respiratory tract infection. He was treated with intravenous co-amoxiclav and supportive therapy, which led to his improvement. The patient was discharged but had to be readmitted a total of four times over the span of 4 months due to recurrent fever and associated symptoms. Transthoracic and transoesophageal echocardiograms and CT of the neck/thorax/abdomen/pelvis were done to look for endocarditis, pacemaker-unit infection and other sources of infection. However, these did not show any evidence of infection. He did have persistent raised inflammatory markers and two blood cultures growing Enterobacter cloacae. A fluorodeoxyglucose positron emission tomography scan was done, which showed evidence of pacemaker lead infection. His pacemaker unit was removed, which led to cessation of his symptoms and normalisation of his inflammatory markers. He had no further hospital admissions to date and has been regularly followed up in an outpatient cardiology clinic.

The impact of global budgeting in Taiwan on inpatients with unexplained fever

Unexplained fever is one of the most common and difficult diagnostic problems faced daily by clinicians. This study evaluated the differences in health service utilization, health care expenditures, and quality of care provided to patients with unexplained fever before and after global budget (GB) implementation in Taiwan.The National Health Insurance Research Database was used for analyzing the health care expenditures and quality of care before and after implementation of the GB system. Patients diagnosed as having unexplained fever during 2000-2001 were recruited; their 2000-2001 and 2004-2005 data were considered baseline and postintervention data, respectively.Data of 259 patients with unexplained fever were analyzed. The mean lengths of stay (LOSs) before and after GB system implementation were 4.22 ± 0.35 days and 5.29 ± 0.70 days, respectively. The mean costs of different health care expenditures before and after implementation of the GB system were as follows: the mean diagnostic, drug, therapy, and total costs increased respectively from New Taiwan Dollar (NT$) 1440.05 ± NT$97.43, NT$3249.90 ± NT$1108.27, NT$421.03 ± NT$100.03, and NT$13,866.77 ± NT$2,114.95 before GB system implementation to NT$2224.34 ± NT$238.36, NT$4272.31 ± NT$1466.90, NT$2217.03 ± NT$672.20, and NT$22,856.41 ± NT$4,196.28 after implementation. The mean rates of revisiting the emergency department within 3 days and readmission within 14 days increased respectively from 10.5% ± 2.7% and 8.3% ± 2.4% before implementation to 6.3% ± 2.2% and 4.0% ± 1.7% after implementation.GB significantly increased LOS and incremental total costs for patients with unexplained fever; but improved the quality of care.

A Diagnostic Tool for Identification of Etiologies of Fever of Unknown Origin in Adult Patients

The diagnosis and treatment of fever of unknown origin (FUO) are huge challenges to clinicians. Separating the etiologies of FUO into infectious and non-infectious disease is conducive to clinical physicians not only on making decisions rapidly concerning the prescription of suitable antibiotics but also on further analysis of the final diagnosis. In order to develop and validate a diagnostic tool to efficiently distinguish the etiologies of adult FUO patients as infectious or non-infectious disease, FUO patients from the departments of infectious disease and internal medicine in three Chinese tertiary hospitals were enrolled retrospectively and prospectively. By using polynomial logistic regression analysis, the diagnostic formula and the associated scoring system were developed. The variables included in this diagnostic formula were from clinical evaluations and common laboratory examinations. The proposed tool could discriminate infectious and non-infectious causes of FUO with an area under receiver operating characteristic curve (AUC) of 0.83, sensitivity of 0.80 and specificity of 0.75. This diagnosis tool could predict the infectious and non-infectious causes of FUO in the validation cohort with an AUC of 0.79, sensitivity of 0.79 and specificity of 0.70. The results suggested that this diagnostic tool could be a reliable tool to discriminate between infectious and non-infectious causes of FUO.

Undifferentiated epithelioid sarcoma presenting as a fever of unknown origin: a case report

Background

Fever of unknown origin is often a diagnostic dilemma for clinicians due to its extremely broad differential. One of the rarer categories of disease causing fever of unknown origin is malignancies; of these, soft tissue sarcoma is one of the least common. Soft tissue sarcomas make up < 1% of all adult malignancies and often do not present with any systemic manifestations or neoplastic fevers.

Case presentation

A 73-year-old Caucasian woman presented with a 2-week history of fever and profound fatigue. The only other symptom she endorsed was a transient history of left knee pain, initially thought to be unrelated. There was no clear cause on initial examination and routine investigations, but her C-reactive protein was significantly elevated at 207 mg/L. Blood cultures and a urine culture were drawn. She was admitted to hospital for further investigation and placed on empiric antibiotics. Her blood cultures were negative, but she had one further fever in hospital. Computed tomography scans did not yield a cause of her fever. No vegetations were seen on echocardiography. Antibiotics were stopped as she did not seem to have an acute infectious cause of her fever. No new symptoms developed. She felt well enough to proceed with out-patient follow up and was discharged after 8 days in hospital. At 1-month post-discharge: no resolution of symptoms, but she endorsed a recurrence of her left knee pain. Ultrasound and magnetic resonance imaging revealed a 4.5 × 6.8 × 11.6 cm soft tissue mass, identified as a sarcoma on biopsy. She subsequently underwent a distal femur resection. Final staging was pT2bN0M0. She underwent adjuvant radiation therapy, but was found to have developed metastatic disease.

Conclusion

This case revealed an atypical presentation of a rare soft tissue sarcoma as the cause of the illness. The etiology behind a fever of unknown origin can be difficult to elucidate, making the approach to investigation particularly important. Repeated history-taking and serial physical examinations can be crucial in guiding investigations and ultimately arriving at a diagnosis. In addition, we believe this case highlights the adage that no seemingly innocuous symptom should be left out when working up a condition with such an extensive and complex differential.

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

Background

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

Methods

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

Results

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

Conclusion

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

67-Gallium SPECT/CT in febrile syndromes of unknown origin

INTRODUCTION AND OBJECTIVE

Febrile syndromes of unknown origin (FSUO) are complex processes in hospital practice. Their management includes an exhaustive medical history and examination, as well as an extensive number of biochemical tests. If these are inconclusive, diagnostic imaging techniques such as SPECT/CT with ⁶⁷-Gallium Citrate (⁶⁷Ga-SPECT/CT) could play an important role. We evaluated its role in the management of FSUO in our healthcare area.

MATERIAL AND METHODS

We reviewed 57 patients who underwent a ⁶⁷Ga-SPECT/CT due to a FSUO (32 women and 25 men, age range: 32-83 years old) obtaining scintigraphic findings, previous treatments and final diagnosis. Values of sensitivity, specificity, positive predictive values (VPP) and negative values (NPV) were obtained and compared with the results for PET/CT with ¹⁸Fluor-deoxy-glucose (¹⁸F-FDG PET/CT) found in the literature.

RESULTS

The diagnoses found were: infection in 27/57 (47%), inflammatory disease in 15/57 (26%), neoplasm in 1/57 (1.75%) and patients without final diagnosis in 14/57 (24%). The statistical values of ⁶⁷Ga-SPECT/CT were: sensitivity, specificity, PPV and NPV of 67%, 93%, 97% y 48%, respectively which were slightly lower than those found for the ¹⁸F-FDG PET/CT (86%, 52%, 70% and 92%, respectively). The diagnostic yield was 73% which increased to 80% in the patients who lacked empirical treatment.

CONCLUSION

Despite the better results of ¹⁸F-FDG PET/CT, ⁶⁷Ga-SPECT/CT behaved as a useful technique in the management of FSUO. It is advisable to use it if ¹⁸F-FDG PET/CT is not available.

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

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

Cost-benefit analysis of introducing next-generation sequencing (metagenomic) pathogen testing in the setting of pyrexia of unknown origin

Pyrexia of unknown origin (PUO) is defined as a temperature of >38.3°C that lasts for >3 weeks, where no cause can be found despite appropriate investigation. Existing protocols for the work-up of PUO can be extensive and costly, motivating the application of recent advances in molecular diagnostics to pathogen testing. There have been many reports describing various analytical methods and performance of metagenomic pathogen testing in clinical samples but the economics of it has been less well studied. This study pragmatically evaluates the feasibility of introducing metagenomic testing in this setting by assessing the relative cost of clinically-relevant strategies employing this investigative tool under various cost and performance scenarios using Singapore as a demonstration case, and assessing the price and performance benchmarks, which would need to be achieved for metagenomic testing to be potentially considered financially viable relative to the current diagnostic standard. This study has some important limitations: we examined only impact of introducing the metagenomic test to the overall diagnostic cost and excluded costs associated with hospitalization and makes assumptions about the performance of the routine diagnostic tests, limiting the cost of metagenomic test, and the lack of further work-up after positive pathogen detection by the metagenomic test. However, these assumptions were necessary to keep the model within reasonable limits. In spite of these, the simplified presentation lends itself to the illustration of the key insights of our paper. In general, we find the use of metagenomic testing as second-line investigation is effectively dominated, and that use of metagenomic testing at first-line would typically require higher rates of detection or lower cost than currently available in order to be justifiable purely as a cost-saving measure. We conclude that current conditions do not warrant a widespread rush to deploy metagenomic testing to resolve any and all uncertainty, but rather as a front-line technology that should be used in specific contexts, as a supplement to rather than a replacement for careful clinical judgement.

Empiric Antibiotic Therapy of Nosocomial Bacterial Infections

Broad-spectrum antibiotics are commonly used by physicians to treat various infections. The source of infection and causative organisms are not always apparent during the initial evaluation of the patient, and antibiotics are often given empirically to patients with suspected sepsis. Fear of attempting cephalosporins and carbapenems in penicillin-allergic septic patients may result in significant decrease in the spectrum of antimicrobial coverage. Empiric antibiotic therapy should sufficiently cover all the suspected pathogens, guided by the bacteriologic susceptibilities of the medical center. It is important to understand the major pharmacokinetic properties of antibacterial agents for proper use and to minimize the development of resistance. In several septic patients, negative cultures do not exclude active infection and positive cultures may not represent the actual infection. This article will review the important differences in the spectrum of commonly used antibiotics for nosocomial bacterial infections with a particular emphasis on culture-negative sepsis and colonization.

Fever of unknown origin revealed to be primary splenic lymphoma: A rare case report with review of the literature

Fever is a common clinical presentation of a number of diseases. A sustained unexplained fever >38.3°C lasting for >3 weeks without an established diagnosis despite intensive diagnostic evaluation is referred to as fever of unknown origin (FUO). FUO remains a clinical challenge for physicians, as it may be attributed to a wide range of disorders, mainly infections, malignancies, non-infectious inflammatory diseases and miscellaneous diseases. We herein report the case of a 59-year-old male patient who presented with prolonged unexplained fever and was found to have a diffusely enlarged hypermetabolic spleen, as shown on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography examination. Following splenectomy, histopathological examination revealed primary splenic lymphoma (PSL) of B-cell origin. The patient received 6 courses of systemic chemotherapy with rituximab, etoposide, cyclophosphamide, doxorubicin, vincristine and prednisone (R-ECHOP regimen) and responded well to treatment. Thus, in patients with FUO and splenomegaly, the possibility of PSL should be taken into consideration.

Chronic Epstein Barr virus infection leading to classical Hodgkin lymphoma

Background

Chronic Epstein Barr virus (EBV) infection in an immunocompetent host has been described however it is not a common entity. It has been linked to many lymphoproliferative disorders and achieves such via many molecular mechanisms, some of which are poorly understood. In addition to infectious mononucleosis, the EBV is linked to various other hematological pathologies and autoimmune disorders.

Case presentation

We describe the case of an elderly immunocompetent female who presented with non-specific symptomatology, lymphadenopathy, cytopenias, elevated autoantibody titers and a crescent EBV viral load that were suggestive of a multisystemic inflammatory disease related to EBV. Extensive work up including multiple bone marrow biopsy and lymphoid tissue procedures ultimately led to the diagnosis of Hodgkin lymphoma.

Conclusion

EBV-related lymphomagenesis is complex and through the utilization of its nuclear antigens and latent membrane proteins the virus is able to shape the microenvironment to promote the various pathologies seen. Moreover, the diagnosis of EBV-associated lymphoproliferative disorders might be challenging when they present in immunocompetent individuals. Our case also represents an emphatic reminder for clinicians that spontaneous regression of lymphadenopathy is not exclusive of low-grade lymphoid malignancies.

Clinical Features of Infection in Older Adults

The impact of infectious diseases on older adults is far greater than on younger adults because of significantly higher morbidity and mortality caused by infection. The reasons for this greater impact include factors such as lower physiologic reserve due to age and chronic disease, age-related changes in host defenses, loss of mobility, higher risk for polypharmacy and adverse drug reactions, and being on drugs that increase the risk for infection (e.g., anticholinergic and other sedating medications increase the risk for pneumonia).

Leiomyosarcoma of the Broad Ligament With Fever Presentation: A Case Report and Review of Literature

Introduction

Leiomyosarcoma is a rare gynecologic malignancy that accounts for less than 1% of gynecological malignancies. Leiomyosarcoma of the broad ligament is an even rarer condition. According to Gardner’s criteria, the diagnosis is made when the mass is completely separated from the uterus and adnexa. So far, 23 cases of primary leiomyosarcoma of the broad ligament have been reported in the literature published in English.

Case Presentation

In September 2014, a 55-year-old, gravida 3, para 3 woman with a BMI of 30 and a chief complaint of fever and dizziness was admitted to the infectious-diseases ward of the Pars general hospital affiliated with Iran University of Medical Sciences in Tehran, Iran. Her symptoms had begun two weeks before. The results of a fever workup and examination for infectious, metabolic, and immunologic problems were all negative. Imaging modalities revealed an endometrial polyp, two calcified myoma in the body of the uterus, and a solid, heterogeneous 70-mm mass in the right para-cervical space, posterior to the broad ligament, and far from the ovary. After surgery, a histologic report revealed leiomyosarcoma.

Conclusions

Although a leiomyosarcoma of the broad ligament is rare, practitioners should consider it when dealing with masses in the region of the broad ligament. If there is any suspicion of malignancy, especially in the presence of fever, it is recommended to avoid morcellation during laparoscopy.

Fever of unknown origin in cancer patients

Fever of unknown origin (FUO) remains a challenging clinical problem, namely in patients with cancer. In cancer patients, FUO may be due to the cancer itself, as it is the case of hematological malignancies; digestive tumors (colon cancer, liver metastases) are significantly associated with FUO and infection can be demonstrated in some cases. Prevention with G-CSF and empirical antimicrobial therapy are essential approaches for the management of FUO in cancer patients. New diagnostic approaches, such as PET imaging, should be further evaluated in cancer patients with FUO.

Fever in Children and Fever of Unknown Origin

Fever is the most common symptom in children and can be classified as fever with or without focus. Fever without focus can be less than 7 d and is subclassified as fever without localizing signs and fever of unknown origin (FUO). FUO is defined as a temperature greater than 38.3 °C, for more than 3 wk or failure to reach a diagnosis after 1 wk of inpatient investigations. The most common causes of FUO in children are infections, connective tissue disorders and neoplasms. Infectious diseases most commonly implicated in children with FUO are salmonellosis, tuberculosis, malaria and rickettsial diseases. Juvenile rheumatic arthritis is the connective tissue disease frequently associated with FUO. Malignancy is the third largest group responsible for FUO in children. Diagnostic approach of FUO includes detailed history and examination supported with investigations. Age, history of contact, exposure to wild animals and medications should be noted. Examination should include, apart from general appearance, presence of sweating, rashes, tonsillitis, sinusitis and lymph node enlargement. Other signs such as abdominal tenderness and hepatosplenomegly should be looked for. The muscles and bones should be carefully examined for connective tissue disorders. Complete blood count, blood smear examination and level of acute phase reactants should be part of initial investigations. Radiological imaging is useful aid in diagnosing FUO. Trials of antimicrobial agents should not be given as they can obscure the diagnosis of the disease in FUO.

Solving the fever mystery: Fever and tonsillar ulcer in an elderly patient

Pyrexia of unknown origin in the elderly is not an uncommon clinical problem. In day to day clinical practice, it has been observed that antibiotics are often empirically escalated to ‘treat fever’ in an otherwise well patient. However, this may not be warranted. It is more important that a comprehensive history, detailed physical examination and a systematic evaluation be undertaken to identify the cause so that definitive therapy may be administered. Apart from infection, neoplastic and connective tissue disorders are other common causes of pyrexia of unknown origin which should be considered. We describe our approach for evaluating an 80-year-old man who presented with fever and sore throat.

[Neuroleptic malignant syndrome : Rare cause of fever of unknown origin]

Neuroleptic malignant syndrome (NMS) is a possible cause of fever of unknown origin (FUO) and is a potentially fatal adverse effect of various drugs, especially of neuroleptics. First generation antipsychotics, such as received by the patient described in this article, are more likely to cause NMS than second generation antipsychotics. The key symptoms are the development of severe muscle rigidity and elevated temperature associated with the use of neuroleptic medication. Malignant catatonia (MC) is an important differential diagnosis of NMS. While neuroleptics can trigger NMS and must be immediately discontinued if NMS occurs, neuroleptic therapy represents the first line treatment for MC. This article describes the case of a patient with schizoaffective disorder where initially the diagnosis of NMS was not clear. Eventually, fever and a markedly elevated serum creatine kinase (CK) led to the correct diagnosis and the appropriate therapy with dantrolene, bromocriptine and amantadine. Furthermore, a thorough review of the currently available literature on NMS is provided.

Chronic granulomatous disease presenting as hemophagocytic lymphohistiocytosis: a case report

Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by recurrent infections and a dysregulated inflammatory response. Infection-triggered hemophagocytic lymphohistiocytosis (HLH), which manifests itself as pathologic hyperactive inflammation, has been observed in subjects with CGD. However, there have been no reports of HLH as the initial presentation with subsequent diagnosis of CGD. Furthermore, the primary therapeutic strategy for HLH focuses on immunosuppressive therapies, which limits immune-mediated tissue damage. With immunodeficiency, this therapeutic strategy may worsen the outcome. This article discusses an 8-week-old Hispanic male who presented with fever of unknown origin. The initial diagnostic evaluation demonstrated pathologic hyperactive inflammation, meeting the HLH-2004 diagnostic criteria without an identified infectious etiology. Immunosuppressive therapy was initiated, with subsequent disseminated candida septic shock and sepsis-induced multisystem organ failure. Additional evaluations ultimately established the diagnosis of CGD. We transitioned to an immune-enhancing strategy with granulocyte and immunoglobulin infusions, and intensified antifungal therapies. These interventions ultimately led to the clearance of the fungal infection and the resolution of the hyperactive inflammatory state. This case represents the first reported case of HLH as the presenting finding leading to the subsequent diagnosis of CGD. It serves as a reminder that both immunodeficiency and inflammatory disorders may share features of pathologic hyperactive inflammation and highlights the conundrum that clinicians face when treating HLH in the setting of an unresolved infection. In this case report, we demonstrate that immune-enhancing therapies may aid in the control and the clearance of the infection, thus paradoxically decreasing the pathologic hyperactive inflammatory response.

Fever of unknown origin in a very old patient: beware of the kidney!

ANCA-associated vasculitis affects more than 20 per million of the population per year and prevails in the elderly. Renal involvement, either isolated or in the context of systemic vasculitis, is common. We report the case of an 86-year-old patient who presented with a histologically proven renal limited vasculitis and with fever and fatigue but with normal renal function and urine analysis. Serum creatinine increased and microscopic hematuria became evident only 3 weeks after symptoms onset, whereas ANCA positivity was the only early key to the diagnosis. This case shows that in the elderly an ANCA-related pauci-immune glomerulonephritis in its earliest stages should be suspected in the presence of a fever of unknown origin even if serum and urine analyses are normal.

Diagnosing unexplained fever: can quick diagnosis units replace inpatient hospitalization?

BACKGROUND

Outpatient quick diagnosis units (QDUs) have become an increasingly recognized alternative to hospitalization for the diagnosis of a number of potentially serious diseases. No study has prospectively evaluated the usefulness of QDU for the diagnosis of unexplained fever.

MATERIALS AND METHODS

We prospectively assessed patients referred to QDU due to fever of uncertain nature (FUN), defined as a temperature > 38 °C during at least 1 week and no diagnosis after a previous evaluation. We also evaluated consecutive patients with FUN who were hospitalized during the same period. QDU and hospital costs were analysed by micro-costing techniques.

RESULTS

We evaluated 176 QDU patients and 168 controls. QDU patients were younger and required fewer investigations than controls. QDU patients had higher prevalence of viral infections (36% vs. 8%, P < 0·001) and lower prevalence of bacterial infections (6% vs. 46%, P < 0·001) and malignancies (2% vs. 14%, P < 0·001). While time-to-diagnosis of QDU patients was longer than length-of-stay of controls (25·82 vs.12·89 days, P < 0·001), 56% of QDU patients only required up to two visits. Cost per QDU patient was €644·59, while it was €4404·64 per hospitalized patient.

CONCLUSIONS

QDU patients with FUN were younger and had less serious diseases than controls including more viral and less bacterial infections and fewer malignancies. Mainly owing to untimely diagnostic reports, time-to-diagnosis was longer in QDU patients. Cost-savings in QDU were substantial. Using objective tools to evaluate the condition severity and general health status of FUN patients could help decide the most appropriate setting for their diagnostic study.

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.

[Fever of unknown origin. Infectious causes]

Infectious diseases remain one of the most important causes of fever of unexplained origin (FUO). We review the spectrum of infectious diseases in the different clinical situations of patients with FUO, namely in classical FUO, in patients with HIV infection, in health care-associated or nosocomial FUO, and in immunocompromised patients with FUO. The most important question is which clinical features make a specific disease a candidate to cause FUO.

[Fever of unknown origin]

Fever of unknown origin (FUO) is defined as sustained unexplained fever despite intensive diagnostic evaluation and represents a particular diagnostic challenge. It can be classified into different categories, e.g. classical, nosocomial, neutropenic and HIV-associated FUO, which is based on the patient-specific clinical and immunological situation. Infections, malignant diseases and non-infectious inflammatory diseases have to be considered as the most important causes of FUO; however, no definitive diagnosis can be established in a substantial number of FUO patients despite an extensive diagnostic work-up. The present review focuses on the important diagnostic aspects as well as therapeutic options in FUO patients.

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.