Measuring follow-up completeness.
Completeness of follow-up is often used as a measure of the quality of follow-up, but the method used to compute it is often not declared. An ideal measure should be based on follow-up years instead of patients. Clark, Altman, and De Stavola proposed such a measure, called "C", which is the percentage of the maximum possible follow-up years, as of a given date, that has actually been accounted for or observed. However, such a measure will underestimate the true completeness, because the denominator (maximum possible follow-up years) does not account for unobserved patient deaths occurring before that date, and therefore, it is realistically unachievable. We propose a modification, C*, of Clark's C, which accounts for the effect of unobserved patient deaths in attenuating the maximum potential follow-up, and thus gives a higher percentage for achieved follow-up completeness. We validated this theoretical improvement by comparing the values of C and C* computed for our long-term coronary artery bypass graft patients to the true completeness, which was obtained by using the National Death Index to complete our missing follow-up data. Using Clark's C, the follow-up completeness was 80.4% and using our C* it is 84.5%, whereas the true follow-up completeness based on National Death Index information was 85.0%.
Wu
YingXing
Y
Medical Data Research Center, Providence Health System, Portland, Oregon, USA. yingxing.wu@providence.org
Takkenberg
Johanna J M
JJ
Grunkemeier
Gary L
GL
D002423:Cause of Death; D003266:Continuity of Patient Care / Q000592:standards / Q000706:statistics & numerical data; D001026:Coronary Artery Bypass / Q000379:methods / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D015233:Models, Statistical; D011786:Quality Control; D012042:Registries; D012189:Retrospective Studies; D015996:Survival Rate