Effect of referral bias on assessing survival in ALS.

We assessed the effect of referral bias on patients with ALS treated at our medical center. A total of 132 subjects were treated by our center over the past 3 years. The referral population had a median survival of 29 months compared to 18 months for the local population (p = 0.007). Referral bias should be addressed when assessing the efficacy of self-selected therapies in the setting of a tertiary ALS clinic.