From the Guidelines
A CSF test for HSV-1 encephalitis is performed through a lumbar puncture (spinal tap) procedure, where a healthcare provider inserts a thin needle between two vertebrae in the lower back to collect cerebrospinal fluid, and the lab will perform a polymerase chain reaction (PCR) test on the CSF sample to detect HSV-1 DNA, which is the gold standard diagnostic test with over 95% sensitivity and specificity 1.
Procedure Details
The procedure involves the patient lying on their side in a curled position or sitting leaning forward to widen the spaces between vertebrae. After cleaning and numbing the area, the doctor inserts the needle, collects about 1-2 teaspoons of CSF, and sends it to the laboratory for analysis.
Key Considerations
- The CSF may also show other abnormalities such as elevated white blood cells (pleocytosis), elevated protein levels, and normal glucose levels 1.
- Patients should remain lying down for a few hours after the procedure to prevent post-lumbar puncture headaches.
- The procedure takes about 30 minutes, and results are typically available within 24-48 hours, allowing for prompt initiation of antiviral therapy if HSV encephalitis is confirmed.
Diagnostic Approach
- If the initial CSF PCR is negative, but HSV encephalitis is still suspected, the test may be repeated after 24-48 hours to determine whether it is still negative for HSV by PCR 1.
- A negative HSV PCR result early in the disease process coupled with a negative HSV-specific CSF antibody study sampled 10-14 days after symptom onset effectively rules out the disease 1.
From the Research
Procedure for Performing a Cerebrospinal Fluid (CSF) Test for Herpes Simplex Virus Type 1 (HSV-1) Encephalitis
The procedure for performing a CSF test for HSV-1 encephalitis involves several steps:
- Lumbar puncture: A lumbar puncture is performed to collect a CSF sample from the patient 2, 3, 4.
- Polymerase Chain Reaction (PCR) testing: The CSF sample is then tested for HSV-1 DNA using PCR, which is considered the diagnostic gold standard for HSV-1 encephalitis 2, 3, 5, 4, 6.
- Interpretation of results: The results of the PCR test are interpreted, and a positive result confirms the diagnosis of HSV-1 encephalitis 2, 3, 5, 4, 6.
- Repeat testing: If the initial PCR test is negative, but there is still a high clinical suspicion of HSV-1 encephalitis, repeat testing may be performed within 3 to 7 days 2.
Considerations for CSF Testing
- Timing of sample collection: The timing of CSF sample collection is important, as the sensitivity of PCR testing may decrease over time 6.
- Use of alternative testing methods: Alternative testing methods, such as the BioFire CSF FilmArray Meningitis/Encephalitis Panel, may be used to detect HSV-1 DNA in CSF samples 5.
- Clinical correlation: The results of CSF testing should be correlated with clinical findings and other diagnostic tests to confirm the diagnosis of HSV-1 encephalitis 2, 3, 4.