From the Guidelines
For a patient with suspected Guillain-Barré Syndrome (GBS), the most important lumbar puncture test to order is cerebrospinal fluid (CSF) protein level, along with cell count, as this combination is crucial for identifying albuminocytologic dissociation, a hallmark of GBS 1. The classic finding in GBS is albuminocytologic dissociation, characterized by elevated CSF protein with a normal white blood cell count. This pattern typically develops after the first week of symptoms. Additional routine CSF tests should include glucose measurement, Gram stain, and culture to rule out infectious causes. CSF protein elevation occurs due to inflammation-induced increased permeability of the blood-nerve barrier, allowing proteins to leak into the CSF. The normal cell count helps distinguish GBS from infectious or inflammatory conditions that typically show pleocytosis. Some key points to consider in the diagnosis and management of GBS include:
- Abnormal results in electrophysiological studies and a combination of an increased protein level and normal cell count in cerebrospinal fluid are classic features of GBS, but patients with GBS can have normal results in both tests, especially early in the disease course 1.
- Respiratory function should be monitored in all patients as respiratory failure can occur without symptoms of dyspnoea 1.
- The efficacy of repeat treatment in patients who have shown insufficient clinical response is uncertain; nevertheless, this practice is common in patients who show deterioration after an initial treatment response 1. It's essential to note that CSF findings may be normal early in the disease course (first few days), so clinical presentation and electrophysiological studies remain crucial for diagnosis. If the initial LP is normal but GBS is still suspected, consider repeating the LP after 1-2 weeks as protein levels tend to rise as the disease progresses. Electrodiagnostic studies, such as nerve conduction studies and electromyography, can also be helpful in supporting the diagnosis of GBS, particularly in patients with an atypical presentation 1. In patients with suspected GBS, it is also important to consider other potential causes of weakness and to rule out alternative diagnoses, such as infectious or inflammatory conditions, through appropriate testing and evaluation 1.
From the Research
Lumbar Puncture Tests for Guillain-Barré Syndrome (GBS)
To diagnose Guillain-Barré Syndrome (GBS), several tests can be conducted on the cerebrospinal fluid (CSF) obtained through a lumbar puncture. The key tests include:
- CSF total protein (TP) concentration: Elevated levels of TP in the CSF with normal cell count are a hallmark for the diagnosis of GBS 2.
- Albumin quotient (Qalb): The CSF/serum albumin quotient has method-independent reference ranges and can be used to diagnose blood-nerve barrier dysfunction in GBS 3.
- CSF/serum protein fractioning: This test can help identify impaired blood-CSF barrier function, which is common in GBS patients 2.
Interpretation of Test Results
The diagnostic yield of Qalb and CSF-TP levels can vary, with Qalb having a similar diagnostic yield to CSF-TP for detecting blood-nerve barrier dysfunction in GBS patients 3. The duration from clinical onset to lumbar puncture can affect the diagnostic yield, with longer durations resulting in higher diagnostic yields 3.
Prognostic Indicators
CSF protein levels and plasma neutrophil/lymphocyte ratio (NLR) have been investigated as potential prognostic indicators for GBS. Elevated CSF protein levels have been shown to be negatively correlated with recovery scores, while high NLR levels have been positively correlated with age and baseline disability 4. However, CSF protein level is considered a more reliable parameter for prognosis 4.
Additional Tests
Other tests, such as electrodiagnostic testing and testing for anti-ganglioside antibodies, may also be useful in supporting the diagnosis of GBS, although their clinical value is limited in most patients with typical motor-sensory GBS 5.