Sorry for the delay in response. In my study and experience, less than 50% of SLE pts w/ NP-SLE will have BBB disruption - as measured by the Q albumin. But heres the point to remember. An intact BBB has a Q albumin under 9. Over 9 there is some disruption; In NP-SLE the Q albumin abnormalities indicate mildly affected BBB with a Q albumin of 9-15 (in <50%). This is very different from CNS infection (meningitis, encephalomyelitis) or vascular event/vasculitis where the Q albumin values are very very high, often 50-200. I hope this rectifies the difference between what I said and what Dubois Textbook claims