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

Nuclear Medicine Imaging Tools in Fever of Unknown Origin: Time for a Revisit and Appropriate Use Criteria

Fever of unknown origin (FUO) is a clinical conundrum for patients and clinicians alike, and imaging studies are often performed as part of the diagnostic workup of these patients. Recently, the Society of Nuclear Medicine and Molecular Imaging convened and approved a guideline on the use of nuclear medicine tools for FUO. The guidelines support the use of 2-18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) in adults and children with FUO. 18F-FDG PET/CT allows detection and localization of foci of hypermetabolic lesions with high sensitivity because of the 18F-FDG uptake in glycolytically active cells that may represent inflammation, infection, or neoplasia. Clinicians should consider and insurers should cover 18F-FDG PET/CT when evaluating patients with FUO, particularly when other clinical clues and preliminary studies are unrevealing.

Ammonia detection: A pathway towards potential point-of-care diagnostics

Invasive methods such as blood collection and biopsy are commonly used for testing liver and kidney function, which are painful, time-consuming, require trained personnel, and may not be easily accessible to people for their routine checkup. Early diagnosis of liver and kidney diseases can prevent severe symptoms and ensure better management of these patients. Emerging approaches such as breath and sweat analysis have shown potential as non-invasive methods for disease diagnosis. Among the many markers, ammonia is often used as a biomarker for the monitoring of liver and kidney functions. In this review we provide an insight into the production and expulsion of ammonia gas in the human body, the different diseases that could potentially use ammonia as biomarker and analytical devices such as chemiresistive gas sensors for non-invasive monitoring of this gas. The review also provides an understanding into the different materials, doping agents and substrates used to develop such multifunctional sensors. Finally, the current challenges and the possible future trends have been discussed.

Structured diagnostic scheme clinical experience sharing: a prospective study of 320 cases of fever of unknown origin in a tertiary hospital in North China

BACKGROUND

There has been little research on the long-term clinical outcomes of patients discharged due to undiagnosed fevers of unknown origin (FUO). The purpose of this study was to determine how fever of unknown origin (FUO) evolves over time and to determine the prognosis of patients in order to guide clinical diagnosis and treatment decisions.

METHODS

Based on FUO structured diagnosis scheme, prospectively included 320 patients who hospitalized at the Department of Infectious Diseases of the Second Hospital of Hebei Medical University from March 15, 2016 to December 31,2019 with FUO, to analysis the cause of FUO, pathogenetic distribution and prognosis, and to compare the etiological distribution of FUO between different years, genders, ages, and duration of fever.

RESULTS

Among the 320 patients, 279 were finally diagnosed through various types of examination or diagnostic methods, and the diagnosis rate was 87.2%. Among all the causes of FUO, 69.3% were infectious diseases, of which Urinary tract infection 12.8% and lung infection 9.7% were the most common. The majority of pathogens are bacteria. Among contagious diseases, brucellosis is the most common. Non-infectious inflammatory diseases were responsible for 6.3% of cases, of which systemic lupus erythematosus(SLE) 1.9% was the most common; 5% were neoplastic diseases; 5.3% were other diseases; and in 12.8% of cases, the cause was unclear. In 2018-2019, the proportion of infectious diseases in FUO was higher than 2016-2017 (P < 0.05). The proportion of infectious diseases was higher in men and older FUO than in women and young and middle-aged (P < 0.05). According to follow-up, the mortality rate of FUO patients during hospitalization was low at 1.9%.

CONCLUSIONS

Infectious diseases are the principal cause of FUO. There are temporal differences in the etiological distribution of FUO, and the etiology of FUO is closely related to the prognosis. It is important to identify the etiology of patients with worsening or unrelieved disease.

The Diagnostic Performance of Multi-Detector Computed Tomography (MDCT) in Depiction of Acute Spondylodiscitis in an Emergency Department

Background: The diagnosis of acute spondylodiscitis can be very difficult because clinical onset symptoms are highly variable. The reference examination is MRI, but very often the first diagnostic investigation performed is CT, given its high availability in the acute setting. CT allows rapid evaluation of other alternative diagnoses (e.g., fractures), but scarce literature is available to evaluate the accuracy of CT, and in particular of multi-detector computed tomography (MDCT), in the diagnosis of suspected spondylodiscitis. The aim of our study was to establish MDCT accuracy and how this diagnostic method could help doctors in the depiction of acute spondylodiscitis in an emergency situation by comparing the diagnostic performance of MDCT with MRI, which is the gold standard. Methods: We searched our radiological archive for all MRI examinations of patients who had been studied for a suspicion of acute spondylodiscitis in the period between January 2017 and January 2021 (n = 162). We included only patients who had undergone MDCT examination prior to MRI examination (n = 25). The overall diagnostic value of MDCT was estimated, using MRI as the gold standard. In particular, the aim of our study was to clarify the effectiveness of CT in radiological cases that require immediate intervention (stage of complications). Therefore, the radiologist, faced with a negative CT finding, can suggest an elective (not urgent) MRI with relative serenity and without therapeutic delays. Results: MDCT allowed identification of the presence of acute spondylodiscitis in 13 of 25 patients. Specificity and positive predictive value were 100% for MDCT, while sensitivity and negative predictive value were 68% and 50%, respectively, achieving an overall accuracy of 76%. In addition, MDCT allowed the identification of paravertebral abscesses (92%), fairly pathognomonic lesions of spondylodiscitis pathology. Conclusions: The MDCT allows identification of the presence of acute spondylodiscitis in the Emergency Department (ED) with a satisfactory accuracy. In the case of a positive CT examination, this allows therapy to be started immediately and reduces complications. However, we suggest performing an elective MRI examination in negative cases in which pathological findings are hard to diagnose with CT alone.

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.

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

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

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.

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.

Recent trends in the distribution of causative diseases of fever of unknown origin

Fever of unknown origin is a challenging diagnostic problem and the aim of this research was to analyze trends in the distribution of its causative diseases. This retrospective study makes a comparison between two different clinical series of patients from two different periods: 227 from period 1 (1998-2002) and 602 from period 2 (2008-2012). There were fewer infections (31.72% vs.16.45%) and more miscellaneous causes (5.29% vs. 13.12%) in the period 2 series, whereas no significant differences in autoimmune diseases, malignancies and undiagnosed cases were found. Adult onset Still's disease and lymphoma occupied the largest proportion in autoimmune diseases (75.00%) and malignancies (89.81%), respectively. Interestingly, the autoimmune diseases group, instead of infections, was found to be the leading category of the causative diseases in fever of unknown origin, which is contrary to previous reports. Further, adult onset Still's disease and lymphoma were suggested to be valued more highly in view of the large and rising proportions found in this study. These trends could support the diagnosis and treatment of fever of unknown origin better in the future.

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.

Clinical and hemato-biochemical studies on fever of unknown origin in buffaloes

Aim:

The present study was undertaken to ascertain the clinical observation and haemato-biochemical studies on fever of unknown origin (FUO) in buffaloes which were presented for treatment at the Teaching Veterinary Clinical Complex (TVCC), Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar.

Materials and Methods:

The investigation was conducted on total 106 clinical cases presented at “TVCC, LUVAS, Hisar.” Diseased animals having history of fever and increased rectal temperature were considered for the current study. Diagnosis of FUO was done on the basis of negative parasitological examination, culture examination, fecal and urine test. The cases in which etiology could not be established (such as pneumonia, metritis, traumatic reticuloperitonitis, urinary tract infection, trypanosomosis, diaphragmatic hernia, Brucellosis, and foreign body) were considered as true cases of FUO.

Results:

Out of 106 clinical cases different etiologies were identified in 76 (71.70%) cases including pneumonia, traumatic pericarditis, trypanosomosis, bacteremia, etc. and 30 cases (28.30%) remained undiagnosed even after detailed investigation. The mean rectal temperature (104.43±0.16°F), respiration rate (56.57±1.51/min) and pulse rate (83.40±1.77/min) of animals (n=30) suffering from FUO were significantly higher, whereas ruminal movement (1.00±0.23) was significantly lower compared to healthy control group. The mean value of hemoglobin, lymphocytes, and packed cell volume were significantly lower, whereas mean value of neutrophils was significantly higher compared to that of healthy control animals. Mean value of serum levels of glucose, phosphorus, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phosphokinase (CPK), blood urea nitrogen (BUN), and creatinine were found to be significantly higher, whereas mean value of calcium value was significantly lower in all clinically affected animals compared to the healthy control group.

Conclusion:

About 28.30% cases of fever in buffaloes were found to be of unknown origin. Haemato-biochemical findings in cases of FUO in buffaloes revealed relative neutrophilia with lymphopenia, hyperglycemia, hypocalcemia, hyperphosphatemia, significantly increased AST, ALT, and CPK along with adversely altered kidney function indicators (elevated BUN and serum creatinine).

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.

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.

The diagnostic role of (18)F fluorodeoxyglucose positron emission tomography in patients with fever of unknown origin

BACKGROUND

Identification of aetiology for fever of unknown origin (FUO) is challenging, due to the high rates of undiagnosed cases. The current diagnostic approach includes initially first-line procedures such as general examination and various laboratory tests and basic imaging techniques followed by second-line tests such as more advanced imaging techniques including (18)F fluorodeoxyglucose positron emission tomography (FDG PET) and tissue biopsies. If no diagnosis is obtained, more invasive measures may be in order such as liver biopsy and exploratory laparotomy.

MATERIALS AND METHODS

This review article is based on the relative published material found on MEDLINE and PubMed up to August 2014. We looked for the terms 'fever of unknown origin, FDG PET' in combination with 'cancer, infection and autoimmune disease'.

RESULTS

Several clinical studies have investigated the utility of the FDG PET during the diagnostic approach of FUO. Recent evidence suggests that FDG PET has the advantage of total body imaging and may depict all common causes of FUO such as infections, noninfectious inflammatory causes and tumours because they all exhibit glucose hypermetabolism. Depiction of an abnormal lesion on FDG PET could guide clinicians to the next diagnostic procedure (another imaging method, culture, biopsy or surgery) to establish the diagnosis.

CONCLUSIONS

Emerging evidence suggests that FDG PET, when available, may provide critical diagnostic information early during evaluation of FUO.

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.