The clinician often wishes to summarize the results of follow-up of a series of patients. He may wish to report on one or more treatments or describe the natural history of a disease. If such clinical data are to be used for research purposes, and if they are to be reported in the scientific literature, then two simple guidelines relating to patient follow-up can be offered to enhance their value. (1) Follow-up should be as complete as possible. (2) If durations of follow-up vary, then study results should be reported for specific follow-up intervals.
When sizable numbers of patients are lost to follow-up, the skeptical reader will ask critical questions about patients who did not return for evaluation.1 Might they have had different results from those who returned? How are the results of the study affected if all patients lost to follow-up are assumed to be failures?
Seigel D. Analysis of Follow-up Data. Arch Ophthalmol. 1985;103(5):647-648. doi:10.1001/archopht.1985.01050050039011