Blood Testing for Neurocysticercosis
The enzyme-linked immunotransfer blot (EITB) assay performed on serum is the blood test of choice for diagnosing neurocysticercosis, available through the CDC and select reference laboratories. 1
Primary Serologic Test
Serum EITB using parasite glycoproteins is the confirmatory blood test for neurocysticercosis. 1, 2 This test represents a major diagnostic criterion in the formal diagnostic framework for NCC. 2
Performance Characteristics by Disease Burden
In patients with multiple parenchymal cysts, ventricular disease, or subarachnoid NCC, serum EITB sensitivity approaches 100%. 1
In patients with a single parenchymal lesion or only calcifications, EITB sensitivity is poor and may be falsely negative. 1
Serum testing is generally more sensitive than CSF testing when using the EITB assay. 1
The specificity of EITB is approximately 99%, with minimal cross-reactivity. 3
Tests to Avoid
ELISA tests using crude antigens should generally be avoided due to frequent false-positive and false-negative results. 1 The sensitivity of ELISA is only 41% compared to 86% for EITB. 1 In epidemiological studies, EITB demonstrated significantly higher sensitivity and specificity than ELISA, with ELISA missing all patients who had seizures while EITB detected 29% of this group. 4
Alternative Serologic Tests
Parasite antigen detection assays in serum may be used to confirm diagnosis, though they are less sensitive than EITB. 1
Antigen assays are not currently commercially available in the United States. 1
Positive antigen results correlate with the number of viable cysticerci and may be helpful for serial monitoring in complex cases. 1
Critical Diagnostic Algorithm
The diagnosis requires integration of serology with neuroimaging:
Order serum EITB as the primary blood test when NCC is suspected based on compatible neuroimaging findings. 1, 2
A positive serum EITB plus neuroimaging lesions highly suggestive of NCC constitutes two major criteria, which when combined with one minor criterion (such as seizures) and one epidemiological criterion (residence in or travel to endemic areas) establishes definitive diagnosis. 2
Do not rely on serum EITB alone in patients with single lesions or calcifications, as sensitivity is inadequate in these presentations. 1
Important Caveats
The immunodominant bands on EITB are GP-39 to -42, GP-24, and GP-13, with the 13-14 kDa bands potentially serving as markers of active disease. 5, 6
Both CT and MRI should be performed in addition to serology, as neuroimaging is essential for complete diagnostic evaluation and disease staging. 2
Screen for latent tuberculosis in patients likely to require prolonged corticosteroids, as tuberculomas can mimic NCC on imaging. 2