We thank Dr Wang for his thoughtful analysis of our work and apologize for our mislabeling the Kaplan-Meier curve. The scale is appropriate to the question asked concerning the development of generalized myasthenia gravis.
There are at least 2 reasons why it may not be valid to look at survival in time intervals across a 6-year period. The economist John Maynard Keynes is said to have remarked, "[I]n the long run we are all dead."1 Correspondingly, given enough time, all survival curves tend to converge. Therefore, it may not be useful to look at the entire follow-up period in the presence of long-term survivors. Instead, it may be preferable to look at clinically meaningful spans of time (eg, 5 or 10 years). This will then determine the maximum span of follow-up and the time point when cases should be right censored. This was the approach used in the analysis of the myasthenia gravis data.
Homel P, Kupersmith MJ. Development of Generalized Myasthenia Gravis in Patients With Ocular Myasthenia Gravis—Reply. Arch Neurol. 2003;60(10):1492-1493. doi:10.1001/archneur.60.10.1491-a