Abstract Background Albuminocytologic dissociation in cerebrospinal fluid (CSF) is a diagnostic hallmark of Guillain–Barré syndrome (GBS). Compared to CSF total protein (TP), the CSF/serum albumin quotient (Qalb) has the advantage of method-independent reference ranges. Whether the diagnostic yield differs between Qalb and CSF-TP is currently unknown. Methods We retrospectively analyzed the diagnostic yield (i.e., a value above the URL indicating blood–nerve barrier dysfunction) of Qalb and CSF-TP levels in patients with GBS. We evaluated two different equations (Reiber’s and Hegen’s) for age-adjusted URLs of Qalb and compared results to CSF-TP using the standard URL of 0.45 g/L as well as age-adjusted URLs (by decade of age). Additionally, multivariable logistic regression analysis was used to assess the effect of clinical factors on the diagnostic yield. Results We analyzed 110 patients [62% males; median age 48 (IQR 35–58)] with sensorimotor (68), motor (16), sensory (12) and localized (8) GBS as well as Miller Fisher syndrome (6). Qalb and CSF-TP were highly correlated (r = 0.95, p < 0.001). The diagnostic yield of Qalb was 65% with Reiber’s and 47% with Hegen’s age-adjusted URLs compared to 66% with the fixed CSF-TP URL of 0.45 g/L and 49% with age-adjusted CSF-TP URLs. A longer duration from clinical onset to lumbar puncture was associated with a higher diagnostic yield. Conclusion Qalb strongly correlates with CSF-TP in patients with GBS with a similar diagnostic yield for the detection of a blood–nerve barrier dysfunction. However, the diagnostic yield of both values is lower when using more recent age-adjusted URLs and at earlier timepoints.