Assessment of the Patient with Fever
A new fever in any patient should trigger a targeted clinical assessment guided by the patient's setting and risk factors, rather than reflexive ordering of laboratory tests and imaging studies. 1
Initial Clinical Evaluation
Begin with a focused assessment that includes:
- Respiratory rate measurement – A respiratory rate >25 breaths/min has 90% sensitivity and 95% specificity for pneumonia in long-term care residents 2
- Mental status changes – Altered mentation may indicate aspiration pneumonia, sepsis, or CNS infection 3
- Hydration status – Assess for signs of dehydration which may complicate infection 3
- Medication review – Specifically evaluate for antibiotics or chemotherapy within the past 60 days, as these predispose to C. difficile infection and drug fever 1, 4
- Recent procedures and surgeries – Document any thoracic, abdominal, or pelvic operations, as well as indwelling devices (catheters, prosthetic joints, central lines) 3, 4
Systematic Physical Examination
Direct attention to the most common infection sources:
- Oropharynx and conjunctiva – Examine for pharyngitis, dental abscess, or conjunctivitis 3
- Chest auscultation – Listen for crackles, decreased breath sounds, or consolidation 3
- Skin examination – Turn the patient to inspect for pressure ulcers, surgical site infections, and cellulitis, particularly in the sacral, perineal, and perirectal areas 3, 4
- Cardiac examination – Assess for new murmurs suggesting endocarditis 3
- Abdominal examination – Palpate for tenderness, organomegaly, or peritoneal signs 3
- Indwelling device sites – Inspect all catheter insertion sites for erythema, purulence, or tenderness 3, 4
Risk Factor Assessment
Identify predisposing conditions that guide your differential:
- Diabetes mellitus – Increases risk for skin infections and urinary tract infections 2, 3
- COPD – Predisposes to pneumonia 2, 3
- Poor swallowing/gag reflex – Raises concern for aspiration pneumonia 2, 3
- Indwelling urinary catheter – Associated with 39-fold increased risk of bacteremia 3
- Prosthetic devices – Consider septic arthritis in patients with artificial joints 2, 3
- Chronic immobility – Evaluate for pressure ulcers 2, 3
Core Diagnostic Studies
After clinical assessment, obtain targeted testing:
Imaging
- Chest radiograph – Obtain in all febrile patients, as pneumonia is the most common infection causing fever in hospitalized patients 5, 4
- CT imaging – Perform for patients with recent thoracic, abdominal, or pelvic surgery if initial workup does not identify an etiology 5, 4
- Abdominal ultrasound – Obtain formal bedside ultrasound if patient has abdominal symptoms, abnormal physical exam, or elevated transaminases/alkaline phosphatase/bilirubin 5
Microbiologic Studies
- Blood cultures – Collect at least two sets (ideally 60 mL total) from different anatomical sites simultaneously, without time interval between them 5, 4
- Central line cultures – If central venous catheter present, draw simultaneously from catheter and peripheral site to calculate differential time to positivity; sample at least two lumens 5, 4
- Respiratory specimens – Obtain lower respiratory tract sample (sputum, tracheal aspirate, or bronchoalveolar lavage) before antibiotic initiation if pneumonia suspected 1, 4
- Urine culture – Only if pyuria present and UTI suspected; replace urinary catheter first and culture from newly placed catheter 5, 4
- Stool testing – Test for C. difficile toxin if diarrhea present and patient received antibiotics/chemotherapy within 60 days 1, 4
Viral Testing
- Respiratory viral panel – Consider viral nucleic acid amplification testing if patient has new cough or upper respiratory symptoms 5, 4
Temperature Measurement Considerations
Use the most accurate method available:
- Preferred methods – Pulmonary artery catheter thermistor, bladder catheter thermistor, or esophageal probe provide core temperature readings 1, 4
- Rectal temperature – More accurate than oral or axillary methods in long-term care residents 2
- Electronic thermometry – Superior to standard mercury thermometry 2
- Avoid – Axillary, tympanic, or temporal artery measurements when core temperature assessment is critical 4
Temperature Thresholds
Different populations require different fever definitions:
- Long-term care residents – Temperature ≥100°F (37.8°C) has 55% positive predictive value for infection; alternatively, temperature increase ≥2°F (1.1°C) over baseline, or oral temperature ≥99°F (37.2°C), or rectal temperature ≥99.5°F (37.5°C) on repeated measurements 2
- General hospitalized patients – Temperature >38.3°C (100.9°F) typically used as threshold 1
Advanced Evaluation for Unclear Source
If initial workup fails to identify etiology:
- 18F-FDG PET/CT – Consider if transport risk acceptable; has sensitivity of 85-100% for identifying occult infection 5, 4
- Thoracic ultrasound – May identify pleural effusions and parenchymal pathology if chest radiograph abnormal and expertise available 5, 4
Biomarkers
Use selectively based on pretest probability:
- Procalcitonin or CRP – Measure when bacterial infection probability is low-to-intermediate, in addition to clinical evaluation 4
- Do not use – PCT or CRP to rule out infection when bacterial infection probability is high 4
Critical Pitfalls to Avoid
- Avoid automatic order sets – Let clinical assessment guide testing rather than reflexively ordering all possible cultures and imaging 1
- Do not culture urine routinely – Avoid urine cultures in catheterized patients without pyuria or UTI symptoms 4
- Do not send stool cultures routinely – Only culture stool if patient admitted with diarrhea, is HIV-positive, or part of outbreak investigation 1
- Consider noninfectious causes – Drug fever, venous thrombosis, pulmonary embolism, acute MI, pancreatitis, and malignancy can all present with fever 5
- Recognize atypical presentations – Elderly and immunocompromised patients may have serious infections without fever 6
Special Considerations by Setting
Long-Term Care Facilities
- Geriatric nurse practitioners can enhance identification of acute problems including fever, though they do not alter overall functional outcomes 2, 3
- Certified nursing assistants often miss infections, attributing symptoms to "colds" when pneumonia, UTI, or skin infections are present 3