When CIDP is suspected, CSF can be tested. A significantly increased protein level is found in 80% of patients, usually between 50 and 200 mg/dL, although it can be higher with a normal white blood cell count in the CSF. In atypical CIDP variants such as the asymmetric subtype, protein levels may not be elevated or may be elevated to a lesser extent than in typical CIDP. In addition, 10% of patients have mild lymphocytic pleocytosis (< 50 cells) and increased gamma-globulin (usually seen in patients with comorbid HIV infection).
NCS and EMG can be helpful in supporting a clinical diagnosis of CIDP. Main abnormalities noted on NCS are demyelinating-range slowed conduction velocities of the nerves (median nerve at the forearm < 30 m/sec, for instance), conduction block, and temporal dispersion. Genetic testing can be useful in certain instances and can be considered on a case-by-case basis. For example, in patients with a positive family history; an insidious symmetric disease course; or some atypical features, including lack of treatment effect, genetic testing for Charcot-Marie-Tooth disease might be indicated as part of the differential diagnosis. Charcot-Marie-Tooth disease type 1X and adult-onset Charcot-Marie-Tooth disease type 1B have been confused with CIDP. Testing for hereditary neuropathy with predisposition to pressure palsies may also be indicated in some patients.
Imaging studies, such as MRI and ultrasound, can provide supportive diagnostic evidence. For example, MRI of the spine with gadolinium enhancement may show enhancement of nerve roots.
Complete blood cell count, sedimentation rate, antinuclear antibody, biochemistry profile, and serum and urine immunoelectrophoresis are all necessary to rule out important associated systemic disorders, such as lupus.
Learn more about other critical tests for the diagnosis of CIDP.
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Cite this: Jafar Kafaie. Fast Five Quiz: Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) Presentation and Diagnosis - Medscape - Jun 30, 2021.