For each of the following patients suspected of having a central nervous system infection, select the most appropriate targeted cerebrospinal fluid laboratory test to order next.
- A 40-year-old man with untreated HIV (CD4 count of ) who has a 3-week history of diffuse headache, nausea, and bilateral papilledema, but lacks nuchal rigidity.Cerebrospinal fluid cryptococcal antigen testing
- A 55-year-old woman who arrives with a 24-hour history of high fever, profound lethargy, and a new-onset generalized tonic-clonic seizure preceded by an olfactory aura.Cerebrospinal fluid herpes simplex virus polymerase chain reaction
- A 68-year-old man who develops acute meningoencephalitis and asymmetric flaccid weakness in his left upper extremity during the late summer.Cerebrospinal fluid West Nile virus IgM antibodies
- A 19-year-old military recruit living in barracks who presents with an abrupt onset of severe neck stiffness, photophobia, and a non-blanching petechial rash.Cerebrospinal fluid Gram stain and bacterial culture
Answer
Patient 1 requires Cryptococcal antigen testing, Patient 2 requires HSV PCR, Patient 3 requires West Nile virus IgM, and Patient 4 requires Gram stain and culture.
Each patient's clinical scenario contains specific pathognomonic features or risk factors that dictate the most appropriate targeted CSF laboratory test. The advanced HIV patient with high intracranial pressure requires cryptococcal antigen testing; the patient with temporal lobe signs needs HSV PCR; the patient with late summer flaccid paralysis needs West Nile virus IgM; and the military recruit with a petechial rash requires Gram stain and bacterial culture.
Step-by-Step Solution
Key Concept
Selection of targeted cerebrospinal fluid laboratory tests based on distinct clinical presentations, host risk factors, and epidemiologic clues of central nervous system infections.