Laboratory Workup for Headache in HIV/AIDS Patients
For HIV/AIDS patients presenting with headache, a comprehensive laboratory workup should include CD4 count, HIV viral load, complete blood count with differential, chemistry panel, and brain imaging with CT or MRI based on CD4 count. 1, 2
Initial Assessment
- CD4 cell count with percentage should be obtained as it is the primary marker of immune function and disease progression in HIV/AIDS patients 3, 1
- HIV RNA viral load testing is essential to assess disease status and response to antiretroviral therapy 3, 1
- Complete blood count with differential white blood cell count should be performed to assess for anemia, leukopenia, and thrombocytopenia which are common in HIV-infected persons 3, 4
- Chemistry panel should be obtained to evaluate renal and hepatic function 3, 1
Neuroimaging Based on CD4 Count
- Brain CT scan with contrast is indicated for all HIV/AIDS patients with headache who have CD4 counts less than 200 cells/μL due to high prevalence of positive findings 2
- For patients with CD4 counts equal to or greater than 200 cells/μL presenting with uncomplicated headache, MRI may be more appropriate than CT due to low prevalence of positive CT findings 2
- All cases of mass lesions or white matter lesions are significantly more likely to occur in patients with CD4 counts less than 200 cells/μL (p = 0.04) 2
Additional Testing Based on Clinical Presentation
- Lumbar puncture should be considered if there is clinical suspicion of meningitis, encephalitis, or CNS opportunistic infections, particularly in patients with CD4 counts <200 cells/μL 1
- Screening for opportunistic infections should be performed, especially in patients with low CD4 counts 3, 1
- Toxoplasma gondii screening by measuring anti-Toxoplasma IgG should be performed as part of the workup 1
- Tuberculosis screening using either tuberculin skin test (TST) or interferon-γ release assay (IGRA) should be included 3, 1
Monitoring Parameters
- Fasting lipid profile should be obtained due to increased cholesterol and triglyceride levels associated with HIV infection, antiretroviral drugs, and host factors 3, 1
- Fasting glucose level should be tested to screen for glucose intolerance and diabetes 3, 5
- Urinalysis and calculated creatinine clearance should be performed, especially in black HIV-infected patients and those with advanced disease or comorbid conditions due to increased risk of nephropathy 3, 1
- Qualitative screening for G6PD deficiency should be considered upon entry into care or before starting therapy with oxidant drugs in patients with predisposing racial or ethnic backgrounds 3
Importance of CD4 Count in Diagnostic Decision-Making
- CD4 count is a stronger predictor of opportunistic illness risk than CD4 percentage 6
- The absolute CD4 count is the more important measure of immune status and should be prioritized when making diagnostic and treatment decisions 6
- Patients with CD4 counts <200 cells/μL have significantly higher risk of developing AIDS-defining illnesses, including those affecting the central nervous system 6
- There is a positive correlation between CD4 cell count and platelet count (r = 0.347), which may be relevant when interpreting laboratory results 7
Monitoring Immune Activation
- Percentage of large unstained cells (%LUCs) on complete blood count may serve as a potential marker of immune activation in HIV infection 8
- Total white cell count shows significant differences in HIV-infected individuals and correlates with markers of immune activation and disease progression 8
- Regular monitoring of CD4/CD8 ratio provides valuable information about immune function and recovery in HIV/AIDS patients 7