From the Guidelines
The diagnostic approach for a patient with fever should begin with a thorough clinical evaluation, including a complete history and physical examination, followed by targeted investigations, as recommended by the most recent guidelines from the Society of Critical Care Medicine and the Infectious Diseases Society of America 1. The clinical evaluation should focus on identifying potential sources of infection, including fever pattern, duration, associated symptoms, recent travel, exposures, and medical history.
- A complete blood count to detect leukocytosis or leukopenia
- Comprehensive metabolic panel to assess organ function
- Urinalysis
- Blood cultures before starting antibiotics
- Chest X-ray to identify pulmonary infections
- Specific tests like malaria smears, viral studies, or specialized cultures based on clinical suspicion For persistent unexplained fever, additional investigations might include:
- Inflammatory markers (ESR, CRP)
- Imaging studies (CT, MRI, ultrasound)
- Possibly lumbar puncture if meningitis is suspected The diagnostic approach should be sequential, starting with non-invasive tests and progressing to more specialized investigations based on initial findings, as suggested by the guidelines 1. This systematic approach helps identify the cause of fever efficiently while avoiding unnecessary testing, as fever can result from infectious, inflammatory, malignant, or medication-related causes. In patients who develop fever during ICU stay, a chest radiograph is recommended as part of the diagnostic workup 1. For patients who have recently undergone thoracic, abdominal, or pelvic surgery, CT scan is recommended as part of a fever workup if an etiology is not readily identified by initial workup 1. The use of antipyretic medications for the specific purpose of reducing temperature is not recommended, unless the patient values comfort by reducing temperature 1.
From the Research
Diagnostic Approach for Fever
The diagnostic approach for a patient presenting with fever involves both clinical evaluation and investigations. The following steps can be taken:
- Complete assessment, including a thorough physical assessment and an evaluation of the history of present illness as well as a detailed review of all the patient's medications 2
- Infection should always be a primary consideration for the cause of a fever, and evaluating each body system can match symptoms with a possible cause for fever 2
- Noninfectious causes of fever need to be included in the differential diagnostic process 2
- Characteristic history and physical examination findings together with key nonspecific test abnormalities are the basis for a focused clue-directed fever work-up 3
Clinical Evaluation
The clinical evaluation of a patient with fever should include:
- Comprehensive history and physical examination to help narrow potential etiologies 4
- Evaluation for infectious etiologies, malignancies, inflammatory diseases, and miscellaneous causes such as venous thromboembolism and thyroiditis 4
- Physical examination and routine laboratory work, such as complete blood count (CBC), are essential components of the evaluation 5
Investigations
The investigations for a patient with fever may include:
- Blood and urine cultures 4, 5
- Imaging studies, such as computed tomography (CT) or 18F fluorodeoxyglucose positron emission tomography (PET) scan 4
- Laboratory tests, such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) levels, and lactate and procalcitonin (PCT) concentrations 4, 5
- Tissue biopsy, such as liver, lymph node, temporal artery, skin, skin-muscle, or bone marrow biopsy, if noninvasive diagnostic tests are unrevealing 4