Design, Setting, and Participants Cases (n = 2014) with a first acute nonfatal MI and population - based controls (n = 2014) living in Costa Rica between 1994 and 2004, matched for age, sex, and area of residence, were genotyped
by restriction fragment —
length polymorphism polymerase chain reaction.
By the 1990s, DNA testing had advanced somewhat through the use of
restriction fragment length polymorphism, but that technique required more material than was available.