Lab testing results are very reliable in the United States. Testing is held to very high state and federal standards, according to Lab Tests Online.
Laboratories have rigorous standards placed on them at the state and federal levels, and they must pass these standards before they ever start testing. Labs must perform tests routinely to prove quality control, for example, and they also require proficiency testing. Proficiency testing is accomplished through challenge samples submitted by an outside agency, where the testing outcome is already known. Each lab must have policies as well as standard procedures codified in writing. These procedures explain how samples are gathered, transported, assessed and reported, states Lab Tests Online.