Initial CSF protein predicts treatment response in chronic inmmune mediated demyelinating polyneuropathy (CIP)

Background: Chronic inflammatory demyelinating polyneuropathy (CIDP) is a heterogenous disease of probably autoimmune origin. Recently published criteria give consideration to its clinical heterogeneity as well as to the impact of positive treatment response in making the diagnosis ex iuvantibus. Beyond intravenous immunoglobulins (IVIg), steroids, azathioprine, mycophenolate, ciclosporine, cyclophosphamide or plasma exchange are accepted as standard or escalating treatment options.

Objective: To define the positive predictive value for treatment response of elevated cerebrospinal fluid (CSF) protein in CIDP patients.

Patients and methods: CSF protein pre-treatment levels at time of diagnosis of 72 patients with positive EFNS criteria for CIDP were analysed retrospectively. CSF protein up to 420mg/l was assessed to be normal. For statistical analysis total positive rate (TPR); total negative rate (TNR), positive and negative preditive values (PPV, NPV), and finally likelihood ratios (LHR) were calculated to evaluate positive tretament prediction.

Results: The LHR of patients with a more than than two-fold increase in CSF protein (i.e. >840mg/l) and IVIg application was 2.5 and their PPV 91% (TPR 0.55, TNR 0.78, NPV 0.29). Other immune therapies did not show higher LHR in these patients.

Conclusion: The odds for a positive treatment response to IVIg is 2.5-fold higher in CIDP patients with CSF protein elevation >840mg/l than in patients with lower CSF values. Prospective data should be collected to prove the clinical validity and usefulness of CSF protein elevation as a predictive marker in CIDP.