Demographic and clinical variables in patients with and without the prediagnostic image available. Number denotes row number (percentage) (A) and median (range) (B) Statistical significance was evaluated using χ2 (A) and the Mann–Whitney U test (B)
| Prediagnostic MRI available (n=41) | Prediagnostic MRI not available (n=13) | Significance | |
| Gender (females)* | 26 (63.4) | 12 (92.3) | 0.047 |
| Age at MS diagnosis† | 27 (9–42) | 32 (19–41) | 0.115 |
| Age at PML diagnosis† | 39 (22–60) | 43 (38–56) | 0.042 |
| MS duration (years)† | 11 (4–36) | 13 (2–24) | 0.617 |
| Past immunosuppression (yes)* | 11 (26.8) | 3 (27.3) | 0.788 |
| Number of NTZ infusions† | 41 (10–86) | 33 (15–54) | 0.388 |
| EDSS at NTZ start† | 3 (0–6.5) | 4.5 (1–7) | 0.120 |
| EDSS at PML diagnosis† | 4 (0–8.5) | 6 (1–8) | 0.367 |
| CSF JCV (copies/mL)† | 113 (0–26300) | 131 (13–3330) | 0.646 |
CSF, cerebrospinal fluid; EDSS, Expanded Disability Status Score; JCV, JC virus; MS, multiple sclerosis; NTZ, natalizumab; PML, progressive multifocal leucoencephalopathy.