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Note added at 4 mins (2009-05-19 17:47:00 GMT)
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Еще вариант: невозможность последующего наблюдения

...в связи с высокой частотой потерь для наблюдения в детской популяции


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Note added at 5 мин (2009-05-19 17:48:10 GMT)
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Это составило 23,6% исходов операций, не потерянных для наблюдения.Табл. 1 наглядно демонстрирует, что метод избранной реконструкции существенно влияет на ...
www.mediasphera.ru/journals/pirogov/detail/226/3292
Период наблюдения за когортой составляет свыше 50 лет. В последнее время предпринимаются значительные усилия к снижению числа потерянных для наблюдения лиц ...
nuclear.tatar.mtss.ru/fa000503.htm

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Note added at 51 mins (2009-05-19 18:33:32 GMT)
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Six withdrawals: infected ulcers (controls only), 2; protocol violation, 1; **lost to follow-up, 3**

http://www.hta.ac.uk/fullmono/mon421.pdf

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Note added at 55 mins (2009-05-19 18:37:42 GMT)
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SUMMARY
The only way to ensure that **losses to follow-up** have not biased study results is to keep all losses to an absolute minimum. Since more complete follow-up leads to the identification of additional disease events, the effort spent in locating cohort members also improves the precision as well as the validity of the study results.
This presentation reviewed approaches for maximizing retention and minimizing loss to follow-up, including the importance of communicating the expectations of participation and collecting personal information at baseline, conducting frequent personal and mail contact, and providing incentives for participation. Response rates can be increased by repeated
attempts to contact each cohort member using a range of approaches (e.g., telephone, mail, personal contacts) and by other procedures specific to mailed questionnaires, telephone interviews, or in-person visits.
**Lost participants** can be traced by use of the NCOA system and contact with other local, state, and national sources. ...
http://epirev.oxfordjournals.org/cgi/reprint/20/1/57

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Note added at 57 mins (2009-05-19 18:40:24 GMT)
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...The percentage of patients **lost to follow-up** (for any reason) varied from **16%** [1] to 70% [13], and the average **rate of loss to follow-up** was **32.5%**. ...
http://ccforum.com/content/11/1/R27

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Note added at 1 hr (2009-05-19 18:47:48 GMT)
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Definitions

For this review, “retention” refers to patients known to be alive and receiving highly active ART at the end of a follow-up period. “Attrition” is defined as discontinuation of ART for any reason, including death, loss to follow-up, and stopping ARV medications while remaining in care. Transfer to another ART facility, where reported, is not regarded as attrition—patients who transfer are assumed to be retained. We accepted the **varying definitions of loss to follow-up** used by the respective studies. Many studies considered ****patients lost if they were more than 3 mo late for a scheduled consultation or medication pickup****, but some studies used more or less stringent definitions ranging from 1 to 6 mo late for a scheduled consultation or medication pick-up.

http://www.plosmedicine.org/article/info:doi/10.1371/journal...