Identifying the Probable Etiology of Acute Undifferentiated Fever through Inflammatory Markers.

BACKGROUND: Acute undifferentiated fever (AUF) is defined as any febrile illness with a duration of ≤14 days without evidence of localized infection. Most outpatient services and a significant inpatient load in India are contributed by AUF. COVID-19 has recently added to the existing list of common etiologies of AUF. While the rapid diagnostic test (RDT) kits, which are widely used for the detection of common etiologies of AUF, are unreliable, the rise of various inflammatory markers may help identify the probable etiology. This not only results in better diagnosis but also prepares the physician for close monitoring and pooling of resources. AIM: To identify the probable etiology of AUF through inflammatory markers. OBJECTIVE: To understand the clinical and biochemical parameters as possible predictors of adverse outcomes in AUF. MATERIALS AND METHODS: This was a prospective observational study carried out in the Department of Medicine in a tertiary care hospital. The total duration of the study was 1 year. A total of 400 AUF patients [both outpatient department (OPD) and inpatient department (IPD)] fulfilling the eligibility criteria were taken up for the study after consent. Various inflammatory markers, namely erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), D-dimer, ferritin, and procalcitonin levels along with basic blood and biochemical tests were measured in all qualifying patients at their first visit. The level of rise of all the measured inflammatory markers was analyzed for clues toward identifying the etiology. Also, the possible predictors of adverse outcomes, as defined in the study, were analyzed. Outcome variables are described as mean ± standard deviation. All statistical calculations were done using computer programs Microsoft Excel 2007 (Microsoft Corporation, New York, United States of America) and SPSS (Statistical Product and Service Solutions; SPSS Inc., United States of America) version 21. RESULTS: The common etiologies in our study contributing to AUF were dengue (31.5%), COVID-19 (18.5%), enteric fever (12.7%), scrub typhus (9.0%), and malaria (6.0%). In 76 cases (19%), the fever was undiagnosed. Enteric fever had highly elevated CRP (>30 mg/L) and moderately elevated D-dimer, ferritin, and procalcitonin. Both nonsevere dengue and COVID-19 had highly elevated D-dimer (>750 ng/mL), but in nonsevere dengue, CRP, ferritin, and procalcitonin were only mildly elevated, whereas in COVID-19, CRP and ferritin were moderately elevated with mildly elevated procalcitonin. Scrub typhus had highly elevated CRP and ferritin [more than four times the upper limit of normal (ULN)], but D-dimer and procalcitonin were only mildly elevated. The mean serum procalcitonin level in enteric fever is significantly higher than the other etiologies of AUF. Our study was correctly able to identify 90.8% of nonsevere dengue, 87.8% of typhoid, 83.6% of COVID-19, and 91.4% of scrub typhus patients based on the inflammatory markers level. Obesity, diabetes (both types 1 and 2), hypertension, coronary artery disease (CAD), malignancy, chronic kidney disease (CKD), and chronic lung disease were significantly associated with adverse outcomes. A significant delay in visiting the hospital after the onset of fever was found in all etiologies of AUF, which had adverse outcomes. CONCLUSION: Our study is one of the few studies comparing the rise in the level of various inflammatory markers among the common etiologies of AUF. The novelty of the study is that it aids in identifying the probable etiology of AUF with good confidence through the levels of inflammatory markers. Also, our study highlights the high-risk factors associated with adverse outcomes in AUF.

Pyrexia of unknown origin as clinical presentation of Renal Cell Carcinoma: Role of F18-FDG PET/CT.

The synergy of the anatomic-metabolic details provided by PET-CT plays a substantial role in the diagnostic workup of Pyrexia of Unknown Origin (PUO). Although several imaging modalities have been used in the detection of cause of PUO, PET-CT is the most sensitive and specific modality for detection of cause. RCC is a rare cause of PUO.

Clinical significance of pre-transplant circulating CD3+ CD4+ CD161+ cell frequency on the occurrence of neutropenic infections after allogeneic stem cell transplantation.

BACKGROUND: Few studies have been performed to identify factors that are associated with an increased risk of infections during the neutropenic period in patients undergoing allogeneic stem cell transplantation (allo-SCT). The aim of this study was to identify the host immune cells responsible for infections before engraftment. METHODS: A total of 282 patients who underwent allo-SCT were enrolled. Peripheral blood samples were collected before conditioning therapy. Expression of CD161-expressing T cells, natural killer cells, and immature myeloid cells was analyzed by flow cytometry. Microbially and clinically defined infections and fevers of unknown origin as proposed by the Immunocompromised Host Society were included in this study. RESULTS: The median age was 45 years (range, 16-68 years). Patients had various hematologic disorders and were transplanted from human leukocyte antigen (HLA)-matched siblings, unrelated donors, and familial HLA-mismatched donors. In univariate analysis, younger age and a familial HLA-mismatched donor were risk factors for the occurrence of infections. After adjusting for potential variables in univariate analysis, multivariate analyses revealed that a lower frequency of CD3+ CD4+ CD161+ cells was significantly associated with the occurrence of neutropenic infections. An age of 35 years or younger and allografting from familial HLA-mismatched donors showed a trend toward higher infection rates. CONCLUSION: Our data indicated that a lower frequency of CD3+ CD4+ CD161+ T cells in peripheral blood before conditioning therapy was associated with a higher incidence of infection during the neutropenic period. These results suggest that recipient innate T cells with expression of C-type lectin CD161 can guard against infections before engraftment.

C-reactive protein concentrations can help to determine which febrile infants under three months should receive blood cultures during influenza seasons.

AIM: We explored whether C-reactive protein (CRP) concentrations could indicate which infants with fever without source (FWS) should receive undergo blood culture tests during influenza seasons. METHODS: This retrospective study focused on patients under three months of age with FWS who had received blood culture tests at the West China Second University Hospital Paediatric Emergency Department during the influenza seasons from June 2013 to January 2015. The statistical analysis comprised specificity, sensitivity, multilevel likelihood ratios (LRs), receiver operating characteristic analysis and a multivariate logistic regression model. RESULTS: We enrolled 592 febrile patients and 7.1% had bacteraemia, with levels falling with increasing age. According to the receiver operating characteristic analysis, the optimum threshold of CRP was 30.5 mg/L, and when the CRP level was higher than 30.5 mg/L, the positive LR of bacteraemia was 2.32. In patients aged 29-90 days, when the CRP level was higher than 5 mg/L, the negative LR of bacteraemia was 0.38. In the neonatal group, a CRP level of ≥30.5 mg/L had a positive LR of bacteraemia of 3.55. CONCLUSION: We found that CRP concentrations could indicate which febrile children under three months of age should undergo blood culture tests during influenza seasons.

Anti-MDA5-Positive Dermatomyositis Presenting as Fever of Unknown Origin.

Dermatomyositis is a chronic systemic autoimmune disease characterized by inflammatory infiltrates in the skin and muscle. The wide variability in clinical and serologic presentation poses a diagnostic challenge for the internist. Appreciation of the clinical variants of dermatomyositis allows for expedient diagnosis and avoidance of diagnostic error. We illustrate these challenges with the case of a 51-year-old Vietnamese-American man who initially presented with fever of unknown origin in the absence of overt skin and muscle manifestations. The diagnosis of dermatomyositis was not evident on several clinical encounters due to the absence of these hallmark symptoms. We review the variable clinical manifestations of a subtype of dermatomyositis associated with an autoantibody against melanoma differentiation-associated protein 5 (anti-MDA5) and suggest consideration of dermatomyositis as a diagnosis in patients presenting with systemic illness and markedly elevated ferritin, even in the absence of elevated muscle enzymes and classic autoantibodies.

Adrenomedullin predicts high risk and culture positivity in children with solid tumors suffering from neutropenic fever.

AIM OF STUDY: Neutropenic fever is a source of morbidity and mortality in children with cancer. It is not possible to detect the causative agent in cultures in most cases; the research for a marker that can show the severity of the disease is ongoing. We evaluated the role of adrenomedullin (ADM) at predicting prognosis on patients with febrile neutropenia, which has been proven to be a good prognostic marker for diseases with high morbidity and mortality, such as heart failure, ischemic ventricular dysfunction, sepsis, and systemic inflammatory response syndrome. MATERIALS AND METHODS: We recorded the 36 febrile episodes of 14 children receiving chemotherapy due to solid tumors. There were 10 events with unknown origin in the low-risk group, while in the high-risk group, there were 17 events with unknown origin, 8 events with microbiological origin and 1 event with clinically proven infection. Cultures were positive only in the high-risk group. However, the changes of ADM levels through time periods (first, second, third, and seventh days) were not significant. RESULTS: The first-day plasma ADM levels significantly predicted the presence of culture positivity (AUC 0.628, 95% CI 0.40-0.85, p = 0.303) and high-risk patients with neutropenic fever (AUC 0.76, 95% CI 0.56-0.97, p = 0.016). CONCLUSION: Our study showed that increased plasma ADM was correlated with high-risk neutropenic fever and culture positivity. The ADM levels in the high-risk group were clearly high at the diagnosis and continued to the end of the treatment.

Blood Culture Testing via a Mobile App That Uses a Mobile Phone Camera: A Feasibility Study.

BACKGROUND: To evaluate patients with fever of unknown origin or those with suspected bacteremia, the precision of blood culture tests is critical. An inappropriate step in the test process or error in a parameter could lead to a false-positive result, which could then affect the direction of treatment in critical conditions. Mobile health apps can be used to resolve problems with blood culture tests, and such apps can hence ensure that point-of-care guidelines are followed and processes are monitored for blood culture tests. OBJECTIVE: In this pilot project, we aimed to investigate the feasibility of using a mobile blood culture app to manage blood culture test quality. We implemented the app at a university hospital in South Korea to assess the potential for its utilization in a clinical environment by reviewing the usage data among a small group of users and by assessing their feedback and the data related to blood culture sampling. METHODS: We used an iOS-based blood culture app that uses an embedded camera to scan the patient identification and sample number bar codes. A total of 4 medical interns working at 2 medical intensive care units (MICUs) participated in this project, which spanned 3 weeks. App usage and blood culture sampling parameters (including sampler, sampling site, sampling time, and sample volume) were analyzed. The compliance of sampling parameter entry was also measured. In addition, the participants' opinions regarding patient safety, timeliness, efficiency, and usability were recorded. RESULTS: In total, 356/644 (55.3%) of all blood culture samples obtained at the MICUs were examined using the app, including 254/356 (71.3%) with blood collection volumes of 5-7 mL and 256/356 (71.9%) with blood collection from the peripheral veins. The sampling volume differed among the participants. Sampling parameters were completely entered in 354/356 cases (99.4%). All the participants agreed that the app ensured good patient safety, disagreed on its timeliness, and did not believe that it was efficient. Although the bar code scanning speed was acceptable, the Wi-Fi environment required improvement. Moreover, the participants requested feedback regarding their sampling quality. CONCLUSIONS: Although this app could be used in the clinical setting, improvements in the app functions, environment network, and internal policy of blood culture testing are needed to ensure hospital-wide use.

Lack of Accuracy of Biomarkers and Physical Examination to Detect Bacterial Infection in Febrile Infants.

OBJECTIVES: The aim of this study was to analyze the usefulness of physical examination, C-reactive protein (CRP), procalcitonin (PCT), white blood cell (WBC) count, and absolute neutrophils counts (ANCs) for the diagnosis of invasive bacterial infections (IBIs) and potentially serious bacterial infections in infants younger than the age of 3 months presenting with fever without source (FWS) to the emergency department (ED). METHODS: A descriptive retrospective study that includes all infants aged younger than 3 months who presented with FWS to the ED between July 2008 and January 2012. We evaluated diagnostic performance for each test by receiver operating characteristic curve analysis. Sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were also calculated. RESULTS: Three hundred eighteen patients met the inclusion criteria. Eleven bacteremia (3.5%) and 76 urinary tract infections (23.9%) were diagnosed. To detect IBI, the areas under the curve for the different tests were as follows: PCT, 0.77 (95% confidence interval [CI], 0.57-0.96); CRP, 0.54 (95% CI, 0.36-0.73); ANC, 0.53 (95% CI, 0.34-0.71); and WBC, 0.42 (0.24-0.61). To detect potentially serious bacterial infections, the areas under the curve were as follows: PCT, 0.66 (95% CI, 0.59-0.74); CRP, 0.68 (0.60-0.76); ANC, 0.64 (0.56-0.71); and WBC, 0.66 (0.58-0.72). CONCLUSIONS: Procalcitonin is better than CRP, WBC, and ANC to confirm or dismiss the presence of an IBI in infants aged younger than 3 months presenting with FWS to the ED. However, it could not identify almost 30% of infants with IBI. Most patients diagnosed with IBI (10 of 11) presented abnormal values in at least one of the analytical parameters and/or physical appearance. Four of 5 patients with IBI and well appearing presented abnormal results in at least one of the analytical parameters. Therefore, the development of tools combining different tests including the new biomarkers could increase the reliability of the tests for the diagnosis of IBI in these patients.

Predictive Significance of Peripheral Blood Smears in Patients with Fever of Unknown Origin: A Retrospective Study of 2871 Cases.

BACKGROUND: Fever of unknown origin (FUO) is a common manifestation and diagnostic problem especially in primary care. Pointing out a diagnosis of FUO often requires numerous noninvasive and invasive procedures. Peripheral blood (PB) smear examination frequently provides many timely and valuable diagnostic clues in various disorders. Few assessments of PB smear morphologic examinations used in the diagnostic evaluation of FUO have been reported. METHODS: To determine whether PB smears have important roles in exploring the causes of FUO, we collected PB smears of 2871 FUO patients from Beijing Chao-yang Hospital affiliated to Capital Medical University from September 2012 to August 2014. Combined with relevant clinical data, we analyzed the PB morphologic features in all the FUO patients. RESULTS: We found the presence of atypical lymphocytes (64.33%), nuclear left shift (46.33%), toxic granulation, vacuolization, and 4 cases of malaria in FUO patients, markedly more than the health control group (p < 0.05), and morphologically consistent with the diagnosis of infectious diseases. Notably, the presence of blasts or immature cells in 26 cases (9%o) and the abnormal changes of leukocytes, erythrocytes or platelets in 4 cases provided predictive information for exploring the causes of FUO, followed by bone marrow smears and other procedures to further confirm the diagnosis as hematological diseases, including acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), Evans syndrome, agranulocytosis, immune thrombocytopenic purpura (ITP). CONCLUSIONS: Our findings demonstrate that a timely and careful observing of PB smears is helpful for clarifying the diagnosis and contributes to appropriate treatment in patients with FUO.

[Value of combined measurement of C-reactive protein, erythrocyte sedimentation rate, lactate dehydrogenase and serum ferritin in etiological diagnosis of fever of unknown origin in children].

OBJECTIVE: To study the clinical value of combined measurement of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), lactate dehydrogenase (LDH), and serum ferritin (SF) in the etiological diagnosis of fever of unknown origin (FUO) in children. METHODS: The clinical data of 154 hospitalized children who had FUO for at least two weeks were retrospectively analyzed, and they were classified into infection (n=54), rheumatism (n=67), and tumor (n=33) groups according to the diagnosis at discharge. The levels of CRP, ESR, LDH, and SF were compared between the three groups, and the diagnostic values of the four indices alone or together were analyzed using the receiver operating characteristic (ROC) curve. RESULTS: Serum CRP and ESR levels were elevated in all the three groups, and increased most significantly in the rheumatism group. Serum LDH level was increased most significantly in the tumor group. SF level was significantly increased in the rheumatism and tumor groups. The area under the ROC curve (AUC) of LDH for diagnosing rheumatism and the AUC of ESR and CRP for diagnosing tumors were lower than 0.7 (P>0.05). The AUC of CRP for diagnosing infection and rheumatism was 0.861 and 0.782, respectively. The AUC of ESR for diagnosing infection and rheumatism was 0.770 and 0.743, respectively. LDH had relatively low AUC, sensitivity, specificity, and Youden's index in diagnosing infection and tumors. SF had the highest AUC, sensitivity, and Youden's index in diagnosing infection, but had the lowest specificity. SF had relatively high AUC, sensitivity, specificity, and Youden's index in diagnosing rheumatism, but had relatively low AUC in diagnosing tumor. The four indices had higher AUC, sensitivity, and specificity in diagnosing rheumatism and tumors when measured together than when measured alone. CONCLUSIONS: In the etiological diagnosis of FUO in children, CRP, ESR, LDH, and SF have certain clinical significance in the preliminary diagnosis of rheumatic diseases, but have limited value in the diagnosis and differentiation of infectious diseases and malignant tumors. Combined measurement of the four indices is superior to the determination of each one for the etiological diagnosis of FUO in children.

Performance of Febrile Infant Algorithms by Duration of Fever.

OBJECTIVES: To analyze the performance of commonly used blood tests in febrile infants ≤90 days of age to identify patients at low risk for invasive bacterial infection (bacterial pathogen in blood or cerebrospinal fluid) by duration of fever. METHODS: We conducted a secondary analysis of a prospective single-center registry that includes all consecutive infants ≤90 days of age with fever without a source evaluated at 1 pediatric emergency department between 2008 and 2021. We defined 3 groups based on caregiver-reported hours of fever (<2, 2-12, and ≥12) and analyzed the performance of the biomarkers and Pediatric Emergency Care Applied Research Network, American Academy of Pediatrics, and Step-by-Step clinical decision rules. RESULTS: We included 2411 infants; 76 (3.0%) were diagnosed with an invasive bacterial infection. The median duration of fever was 4 (interquartile range, 2-12) hours, with 633 (26.3%) patients with fever of <2 hours. The area under the curve was significantly lower in patients with <2 hours for absolute neutrophil count (0.562 vs 0.609 and 0.728) and C-reactive protein (0.568 vs 0.760 and 0.812), but not for procalcitonin (0.749 vs 0.780 and 0.773). Among well-appearing infants older than 21 days and negative urine dipstick with <2 hours of fever, procalcitonin ≥0.14 ng/mL showed a better sensitivity (100% with specificity 53.8%) than that of the combination of biomarkers of Step-by-Step (50.0% and 82.2%), and of the American Academy of Pediatrics and Pediatric Emergency Care Applied Research Network rules (83.3% and 58.3%), respectively. CONCLUSIONS: The performance of blood biomarkers, except for procalcitonin, in febrile young infants is lower in fever of very short duration, decreasing the accuracy of the clinical decision rules.

Fever of unknown origin (FUO) in an immunocompetent adult due to cytomegalovirus (CMV) with polyclonal gammopathy.

Fever of unknown origin (FUO) may be due to infection, malignancy, collagen vascular/inflammatory disorders, or other causes. Cytomegalovirus (CMV) infection is a rare cause of FUO in immunocompetent adults. We present a case of FUO due to CMV in an immunocompetent adult with polyclonal gammopathy on serum protein electrophoresis (SPEP).

Adult-onset Still's disease: still a diagnosis of exclusion. A nested case-control study in patients with fever of unknown origin.

OBJECTIVES: Several sets of criteria have been proposed to classify adult-onset Still's disease (AOSD), those of Yamaguchi being the most commonly used. The Yamaguchi criteria demand the exclusion of other conditions. A clinical scale, recently proposed by Crispin et al., but not yet validated, would allow a positive diagnosis of AOSD in a majority of patients, without the need of thorough diagnostic procedures. METHODS: From a database of 447 patients with classical fever of unknown origin (FUO), collected over a 10-year period (2000-2009) at a general internal medicine department of a university hospital, 22 patients with AOSD according to the Yamaguchi criteria were extracted and compared with 44 controls, matched to index year. Clinical and laboratory parameters were recorded. Sensitivity, specificity and accuracy of the Yamaguchi criteria and of the clinical score were assessed. RESULTS: Lower age, joint symptoms, rash, throat ache, neutrophilic leukocytosis, and elevated erythrocyte sedimentation rate were the principal characteristics supporting a diagnosis of AOSD in patients with FUO. Sensitivity, specificity, and accuracy of the Yamaguchi criteria were 95% or more. The clinical scale, while being specific (98%), lacked sensitivity (55%) and had lower accuracy (83%). CONCLUSIONS: In patients with FUO, the Yamaguchi criteria are a time honored and reliable guide to a diagnosis of AOSD. The clinical scale may serve to rule in, rather than to rule out, AOSD. In many patients, Still's disease is still a diagnosis of exclusion.

Comparison of the test characteristics of procalcitonin to C-reactive protein and leukocytosis for the detection of serious bacterial infections in children presenting with fever without source: a systematic review and meta-analysis.

STUDY OBJECTIVE: We determine the usefulness of the procalcitonin for early identification of young children at risk for severe bacterial infection among those presenting with fever without source. METHODS: The design was a systematic review and meta-analysis of diagnostic studies. Data sources were searches of MEDLINE and EMBASE in April 2011. Included were diagnostic studies that evaluated the diagnostic value of procalcitonin alone or compared with other laboratory markers, such as C-reactive protein or leukocyte count, to detect severe bacterial infection in children with fever without source who were aged between 7 days and 36 months. RESULTS: Eight studies were included (1,883 patients) for procalcitonin analysis, 6 (1,265 patients) for C-reactive protein analysis, and 7 (1,649 patients) for leukocyte analysis. The markers differed in their ability to predict serious bacterial infection: procalcitonin (odds ratio [OR] 10.6; 95% confidence interval [CI] 6.9 to 16.0), C-reactive protein (OR 9.83; 95% CI 7.05 to 13.7), and leukocytosis (OR 4.26; 95% CI 3.22 to 5.63). The random-effect model was used for procalcitonin analysis because heterogeneity across studies existed. Overall sensitivity was 0.83 (95% CI 0.70 to 0.91) for procalcitonin, 0.74 (95% CI 0.65 to 0.82) for C-reactive protein, and 0.58 (95% CI 0.49 to 0.67) for leukocyte count. Overall specificity was 0.69 (95% CI 0.59 to 0.85) for procalcitonin, 0.76 (95% CI 0.70 to 0.81) for C-reactive protein, and 0.73 (95% CI 0.67 to 0.77) for leukocyte count. CONCLUSION: Procalcitonin performs better than leukocyte count and C-reactive protein for detecting serious bacterial infection among children with fever without source. Considering the poor pooled positive likelihood ratio and acceptable pooled negative likelihood ratio, procalcitonin is better for ruling out serious bacterial infection than for ruling it in. Existing studies do not define how best to combine procalcitonin with other clinical information.

Serological evidence of rickettsial infections in Delhi.

BACKGROUND & OBJECTIVES: Rickettsial infections remain under-diagnosed due to lack of diagnostic facilities in developing world. Here we present our experience at National Centre for Disease Control, Delhi, about a serosurvey done in Delhi for rickettsial disease with easy to perform low cost, low expertise Weil Felix test. METHODS: On the basis of cut-off titre obtained in healthy population, Weil Felix test results were interpreted along with clinical data. Entomological investigation was also carried out in select areas of Delhi. Rodents were trapped from houses and gardens and vector mites were collected. RESULTS: When serum samples were collected during initial 5 yr period from patients with fever of unknown origin, seropositivity was 8.2 per cent whereas when rickettsial infection was kept as one of the differential diagnosis by clinicians seropositivity increased to 33.3 per cent. Rickettsial infections detected were scrub typhus (48.2%) followed by spotted fever group (27.5%) and typhus group (6.8%) during 2005-2009. In preliminary entomological survey vector mite Leptotombidium deliense was found on rodents. INTERPRETATION & CONCLUSIONS: Our findings showed that results of Weil Felix test should not be disregarded, rather clinically compatible cases should be treated to save lives.

Diagnostic value of F-18 FDG PET/CT in fever or inflammation of unknown origin in a large single-center retrospective study.

Cause determination is challenging in fever or inflammation of unknown origin (FUO/IUO) despite today's diagnostic modalities. We evaluated the value of F-18 FDG PET/CT in an unselected patient collective. This retrospective nonrandomized single-center study enrolled 300 male and female patients with FUO/IUO. PET/CT findings were compared with final clinical outcomes to determine the sensitivity, specificity, clinical significance, etiological distribution of final diagnoses, impact on treatment, role of white-blood cell count (WBC), and C-reactive protein (CRP). In 54.0% (162/300) PET/CT was the decisive exanimation for establishing the final diagnosis, in 13.3% (40/300) the findings were equivocal and indecisive, in 3.3% (10/300) PET/CT findings were false positive, while in 29.3% (88/300) a normal F-18 FDG pattern was present. Statistical analysis showed a sensitivity of 80.2% and a specificity of 89.8% for the contribution of PET/CT to the final diagnosis. CRP levels and WBC were not associated with PET/CT outcome. PET/CT let to new treatment in 24.0% (72/300), treatment change in 18.0% (54/300), no treatment change in 49.6% (149/300), and in 8.3% (25/300) no data was available. Our study demonstrates the utility of F-18 FDG PET/CT for source finding in FUO/IUO if other diagnostic tools fail.