Quantitative polymerase chain reaction: validation of microarray results from postmortem brain studies.

Quantitative polymerase chain reaction (Q-PCR) is now considered the "technique of choice" for validating gene expression changes identified with ribonucleic acid-based expression profiling technologies (especially micro- and macroarray techniques). The identification of altered gene expression profiles with microarrays is best viewed as the first step in the determination of potential disease-associated genes; however, the false-positive rate can be high, particularly with small sample sets and in view of the typically small differences observed in brain expression studies. Quantitative PCR is a rapid and highly sensitive technique for accurate quantification of microarray results; however, careful consideration of experimental design, quality of primer/probe design, internal standards, and normalization procedures are pivotal, particularly when the work involves postmortem tissue.