Table 1.
Demographic characteristics and cerebrospinal fluid (CSF) reports of study population (cohort 1).
| Women (n = 859) |
Men (n = 660) |
p | |
|---|---|---|---|
| Age, years: median (IQR) | 43 (33–57) | 50 (37–65) | <0.0001 |
| CSF IgG (mg/dL): median (IQR) | 3.59 (2.30–5.76) | 4.63 (2.91–7.57) | <0.0001 |
| CSF albumin (mg/dL): median (IQR) | 19.2 (14.6–27.4) | 29.7 (20.4–43.6) | <0.0001 |
| Serum IgG (mg/dL): median (IQR) | 1050 (876–1260) | 1030 (861–1220) | 0.1963 |
| Serum albumin (mg/dL): median (IQR) | 3940 (3630–4260) | 4000 (3583–4408) | 0.0866 |
| Albumin quotient (QAlb) value: median (IQR) | 4.93 (3.70–7.15) | 7.50 (5.12–11.48) | <0.0001 |
| IgG Index (positive): n (%) | 309 (36.0) | 160 (24.2) | <0.0001 |
| Reiber’s formula (positive): n (%) | 315 (36.7) | 127 (19.2) | <0.0001 |
| CSF IgG OCB patterns: n (%) | |||
| Pattern 1 (negative): | 445 (51.8) | 429 (65.0) | <0.0001 |
| Pattern 2 (local synthesis): | 323 (37.6) | 133 (20.2) | <0.0001 |
| Pattern 3 (mixed): | 24 (2.8) | 23 (3.5) | 0.4579 |
| Pattern 4 (mirror): | 57 (6.6) | 61 (9.2) | 0.0320 |
| Pattern 5 (paraproteinemic): | 10 (1.2) | 14 (2.1) | 0.1505 |
The comparison between categorical and continuous variables was made using the Fisher’s exact test and the Mann–Whitney test, respectively. Presence of IgG oligoclonal bands (OCBs) was assessed in all paired CSF and serum samples with the use of isoelectric focusing on agarose gel followed by IgG-specific immunoblotting. According to literature [9], we have identified the following CSF patterns: pattern 1 = absence of IgG OCBs; pattern 2 = 2 or more CSF-restricted IgG OCBs; pattern 3 = 2 or more CSF-restricted IgG OCBs with additional identical IgG OCBs in CSF and serum; pattern 4 = 2 or more identical IgG OCBs in CSF and serum; pattern 5 = some identical IgG OCBs in CSF and serum in a restricted pH range. Accordingly, only patterns 2 and 3 were considered suggestive of an intrathecal IgG synthesis. IQR: interquartile range.