Comparative analysis of albumin quotient and total CSF protein in immune-mediated neuropathies: a multicenter study...

Blood-cerebrospinal fluid (CSF) barrier dysfunction is pivotal for diagnosing immune-mediated neuropathies, especially in spinal nerve root inflammation. Typically, either total CSF protein or the CSF to serum albumin ratio (Q_Alb) is measured. Total CSF protein measurements have limitations, notably its fixed reference value regardless of age, in contrast to the age-dependent reference for Q_Alb. Our goal was to evaluate both markers in patients with immune-mediated neuropathies.

In our multicenter research, we collected retrospective CSF data from patients suffering from immune-mediated neuropathies across four German research centers. These parameters were analyzed in relation to their clinical characteristics.

Out of 419 samples, 36 (8.6%) displayed a notable variation between total CSF protein and Q_Alb values. A detailed analysis revealed that patients displaying elevated Q_Alb but normal total CSF protein levels were significantly younger at disease onset (p = 0.01), at the time of diagnosis (p = 0.005), and when undergoing lumbar puncture (p = 0.001) compared to patients with elevated CSF protein and normal Q_Alb levels. These effects were especially evident for the subgroup of samples derived by female patients.

Our work confirms the crucial role of Q_Alb in diagnosing immune-mediated neuropathies and particularly its efficacy as a marker for evaluating the blood-CSF barrier in patients with an earlier disease onset. Considering the significance of the albumin quotient, its assessment is especially advisable in younger patients of female sex to avoid missing a potential barrier dysfunction that might be falsely negative when using total protein.