October 10, 2014

When is CT + LP indicated in the patient with HIV / AIDS

By Cameron Wangsgard, M.D.


Quick tip for estimating CD4 count in ED

CD4 < 200 significantly raises risk for opportunistic infections.

  • Absolute lymphocyte count < 1000 correlates to CD4 count < 200.
    • Predictive value 91% [1]
  • Absolute lymphocyte count > 2000 correlates to CD4 count > 200.
    • Predictive value 95% [1]

Patient with CD4 <200 or ALC <1000

  • Even vague complaints including fever, headache, and/or malaise may have CNS infections. [2]
  • Obtain CT followed by LP.
    • CSF WBC counts and glucose may appear normal despite a concomitant CNS infection [3]
    • Initiate empiric treatment until cutlures and antigen testing returns.
    • Consider CT with and without contrast
      • Contrast shows ring-ehanching lesions of toxoplasmosis.

Patient with CD4 >200 or ALC >2000

  • Clinical decision rule developed in cohort of 110 HIV positive patients.
    • 100% sensitivity in ruling out new intracranial lesions [4]
      • New or different headache than usual?
      • Headache lasting more than three days?
      • Focal neurologic deficit?
      • Altered mental status?
      • New-onset seizure?
    • If none of these are present, it is considered safe to forego CT and LP.

Special considerations in differential for HIV pt w/ CNS symptoms

  • Includes fever, malaise, headache, focal weakness, etc.
    • Cryptococcal meningitis
    • Toxoplasma gondii
    • Progressive multifocal leukoencephalopathy
    • CNS lymphoma
    • Guillain-Barré

  1. Shapiro, Nathan I., et al. “Absolute lymphocyte count as a predictor of CD4 count.” Annals of emergency medicine 32.3 (1998): 323–328.  ↩
  2. Graham III, Cole Blease, et al. “Screening CT of the brain determined by CD4 count in HIV-positive patients presenting with headache.” American journal of neuroradiology 21.3 (2000): 451–454.  ↩
  3. Clark, Rebecca A., et al. “Spectrum of Cryptococcus neoformans Infection in 68 Patients Infected with Human Immunodificiency Virus.” Review of Infectious Diseases 12.5 (1990): 768–777.  ↩
  4. Rothman, Richard E., et al. “A Decision Guideline for Emergency Department Utilization of Noncontrast Head Computed Tomography in HIV‐infected Patients.” Academic emergency medicine 6.10 (1999): 1010–1019.  ↩

Tags: Core Content, infectious disease, neurology

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