instruction: what were the four most common specimen tests performed until 3 years ago?
response: SELECT t1.culturesite FROM (SELECT microlab.culturesite, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM microlab WHERE DATETIME(microlab.culturetakentime) <= DATETIME(CURRENT_TIME(), '-3 year') GROUP BY microlab.culturesite) AS t1 WHERE t1.c1 <= 4