http://www.thefreedictionary.com/sick list

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Note added at 18 mins (2009-04-22 13:55:30 GMT)
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SICK-LIST
sick-list • (листок временной нетрудоспособности) больничный

http://www.inopedia.com/12/83/1084250.html

That's what I would call it if long-term disability is meant. Sick leave is more reminiscent of больничный, i.e. short-term absence from work due to minor ailments or whatever other personal reasons. In the US, most employers give their workers a set number of paid sick days per year, to be used at will. If you don't use them all up, you can add them up to your annual vacation. If you are lucky enough to have it, that is.

Если речь идет о больничном листе.

...patients who ask for a medical certificate for sick leave are granted the request, and it has been claimed that doctors often issue medical ...
https://www.researchgate.net/publication/13618055_Life_situa... - Similar pages

лист нетрудоспособности - это то же самое, что больничный лист.

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Note added at 18 mins (2009-04-22 13:55:56 GMT)
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Were there any sick leaves within 12 months? 3 weeks in December

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Note added at 6 hrs (2009-04-22 19:59:25 GMT)
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I can see that my proposal was misinterpreted. Let me explain it in detail.

As Steph noted in the subject, it is from a hospital report in Russian. I am working in a hospital myself and I know what it refers to. No one is carrying any documents certifying sick leaves for 12 months with them; in fact, these documents (sick leave records/certificates, as other answerers suggested) are submitted to the employer and, as far as I know, the employee has no copy of it. So being too literal and formal and mentioning exactly the document is not necessary for this context. The important meaning of this line is that when taking history during admission process, physician asks the patient whether (s)he had any official sick leaves during the last 12 months. This information is needed in order to determine whether the patient may potentially qualify for a long-term disability based on total duration of sick leaves within one year. That's it. For a person not familiar with post-Soviet system of sick leave documentation, details about existence of special records out there somewhere are superfluous and might even be misleading.