An automated sample analysis instrument positively identifies and maintains the identity of a plurality of patient samples contained in individual sample containers. The invention prevents sample misidentification, especially when patient sample must be transferred from one sample container to reaction wells in Microtiter.RTM. plates. Rows of reaction wells in Microtiter.RTM. plates are processed in parallel so the difference in reaction time between any two wells on a plate is four minutes or less. Reaction wells are washed with high-pressure jets of wash solution and are aspirated so as to advantageously utilize fluid meniscus on top of fluid contained in the wells. The apparatus can be adjusted to perform a variety of different ELISA-type tests.