Experimental comparison and cross-validation of Affymetrix HT plate and cartridge array gene expression platforms

The successful use of gene expression microarrays in basic research studies has spawned interest in the use of this technology for clinical trial and population-based studies, but cost, complexity of sample processing and tracking, and limitations of sample throughput have restricted their use for these very large-scale investigations. The Affymetrix GeneChip Plate Array System addresses these concerns and could facilitate larger studies if the data prove to be comparable to industry-standard cartridge arrays. Here we present a comparative evaluation of performance between Affymetrix GeneChip Human 133A cartridge and plate arrays with an emphasis on the assessment of systematic variation and its impact on log ratio data. This study utilized two standardized control RNAs on four independent lots of plate and cartridge arrays. We found that HT plate arrays showed improved specificity and were more reproducible over a wide intensity range, but cartridge arrays exhibit better sensitivity. Not surprisingly, artifactual changes due to positional effects were detectable on plate arrays, but were generally small in number and magnitude and in practice may be removed using standard fold-change and p-value thresholds. Overall, log ratio data between cartridges and plate arrays were remarkably concordant. We conclude that HT arrays offer significant improvements over cartridge arrays for large-scale studies.