From the Guidelines
For a patient presenting with global fever, a comprehensive blood workup is recommended to identify the underlying cause, including a complete blood count (CBC), comprehensive metabolic panel (CMP), blood cultures, and C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to measure inflammation levels, as suggested by 1. The initial evaluation of a patient with global fever should prioritize tests that can quickly identify life-threatening conditions, such as severe infections or sepsis.
- Key initial tests include:
- Complete Blood Count (CBC) to assess for infection, inflammation, or blood disorders
- Comprehensive Metabolic Panel (CMP) to evaluate organ function
- Blood cultures to identify potential bacterial infections
- C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to measure inflammation levels
- Liver function tests, as recommended by 1 and 1 Additional tests may be considered based on the patient's travel history, exposure risks, and clinical presentation, such as malaria smears, dengue, or typhoid serologies, as suggested by 1 and 1. It is essential to note that the choice of tests should be guided by the patient's specific clinical presentation and risk factors, and that a systematic approach is necessary to narrow down potential causes of fever, from common infections to more complex systemic disorders, allowing for appropriate and timely treatment, as implied by 1 and 1.
From the Research
Blood Tests for Global Fever
The following blood tests are recommended for a patient presenting with global fever:
- Nonstructural 1 (NS1) antigen rapid diagnostic test (RDT) 2, 3, 4, 5
- Enzyme-linked immunosorbent assays (ELISAs) targeting NS1 antigen 3, 4, 5
- C-reactive protein (CRP) test to predict dengue disease outcome and differentiate dengue from other febrile illnesses 6
- Reverse-transcription polymerase chain reaction (RT-PCR) for diagnosis of dengue fever 3
Key Considerations
- The sensitivity and specificity of NS1 antigen assays vary depending on the test and geographic region 3, 4, 5
- NS1 antigen assays are more sensitive for primary dengue infections and less sensitive for secondary infections 3, 4
- CRP levels can be used to predict disease progression and differentiate dengue from other febrile illnesses 6
- The combination of NS1 and IgM detection in samples collected in the first few days of fever can increase the overall dengue diagnostic sensitivity 5
Test Performance
- The sensitivity of NS1 antigen RDTs ranges from 71.9%-79.1% 4
- The sensitivity of NS1 antigen ELISAs ranges from 85.6-95.9% 4
- The specificity of NS1 antigen assays ranges from 95%-100% 4, 5
- CRP levels can be used to predict disease outcome, with higher levels associated with a higher risk of severe or intermediate outcome 6