Prevalence of Anti-JC Virus (JCV) Antibodies in the Multiple Sclerosis (MS) Population in Cyprus: A Retrospective Study

Table 4

Analysis of seroconversion patterns among patients on natalizumab therapy (n = 121).

	No. of patients (%)	Follow-up time (mean ± SD, person-years)	Annual conversion rate	Mean (SD) duration of natalizumab intake (years)
Seroconversion negative to positive	14 (11.6)	3.10 ± 1.96	4.5%	4.5 (2.3)
Seroconversion positive to negative	5 (4.1)	1.63 ± 1.96	1.7%	5.2 (2.2)
Alternate seroconversions	5 (4.1)	Not available^≠	Not available^≠	4.3 (2.1)

^≠Information not available since several events per patient (alternate seroconversions) do not permit assignment of a specific follow-up time, thus making the calculation of an annual conversion rate impossible.