Assessment according to the proposed case definition (n=119)
| MAB | Underlying disease (as reported) | Total number | Level 1 | Level 2 | Level 3 | Level 4 | Level 5 |
| Natalizumab | MS | 72 (100%) | 25 (34.7%) | 1 (1.4%) | 1 (1.4%) | 16 (22.2%) | 29 (40.3%) |
| Rituximab | Haematological malignancies | 32 | 4 | 1 | 9 | 18 | – |
| RA | 2 | – | – | – | 2 | – | |
| Wegener's granulomatosis | 1 | – | – | – | 1 | – | |
| Underlying disease not reported | 4 | – | – | 1 | 3 | – | |
| Total (rituximab) | 39 (100%) | 4 (10.3%) | 1 (2.6%) | 10* (25.6%) | 24 (61.5%) | – (0%) | |
| Alemtuzumab | B-CLL | 4 | – | – | 1* | 3 | – |
| Efalizumab | Psoriasis | 3 | 1 | – | – | 2 | – |
| Ofatumumab | B-CLL | 1 | 1 | – | – | – | – |
| Total | 119 (100%) | 31 (26.1%) | 2 (1.7%) | 12 (10.1%) | 45 (37.8%) | 29 (24.4%) |
↵* These reports were assessed as level 3 (instead of level 1) solely because the laboratory was not specified in which the PCR for JCV DNA in CSF was performed.
B-CLL, B cell chronic lymphocytic leukaemia; CSF, cerebrospinal fluid; JCV, JC virus; MAB, monoclonal antibody; MS, multiple sclerosis; RA, rheumatoid arthritis.