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Search of Unknown Fever Focus Using PET in Critically Ill Children With Complicated Underlying Diseases

Objectives: PET/CT with 18F-fluorodeoxyglucose can be used to image cellular metabolism and has been used for evaluating fever of unknown origin in adults. However, there are limited studies about the role of 18F-fluorodeoxyglucose PET/CT in evaluation of fever of unknown origin in critically ill children, especially those presenting with complicated underlying diseases under treatment. Here, we report our preliminary experience using 18F-fluorodeoxyglucose PET/CT in this specific group of patients. Design: Retrospective observational study. Setting: PICUs of a university hospital. Patients: Nineteen critically ill children (mean age, 5.7 yr old) with complicated underlying diseases requiring intensive care support underwent 18F-fluorodeoxyglucose PET/CT to evaluate fever of unknown origin. The median hospitalized stay was 34 days (range, 15–235 d) and fever of at least 7 days (mean, 21.6 d; range, 7–52 d). The PET scan was advocated after all routine microbiology, and conventional imaging showed negative or inconclusive results. Interventions: None. Measurements and Main Results: The 18F-fluorodeoxyglucose PET/CT findings (blinded to the final clinical diagnosis) were compared with final histopathology, culture, serology results, or follow-up imaging. A final diagnosis was made in 16 patients (84.2%). 18F-fluorodeoxyglucose PET/CT accurately localized the source of fever in 14 patients, confers to a sensitivity of 87.5% (14 of 16; 95% CI, 0.604–0.978). A false-positive scan in a patient led to subsequent unnecessary investigations. Two false-negative 18F-fluorodeoxyglucose PET/CT images were later attributed to relapse of underlying disease in the bone marrow and renal abscesses, respectively. In the other two patients where 18F-fluorodeoxyglucose PET/CT also showed negative findings, fever subsided shortly thereafter without treatment. Conclusions: Our preliminary experience suggests that 18F-fluorodeoxyglucose PET/CT may be clinically beneficial in evaluating fever of unknown origin in children with complicated underlying diseases mandating intensive support in ICUs if usual investigative methods are unsuccessful. Further large prospective studies are needed to validate these findings.