Rapid quantification of DNase I activity in one-microliter serum samples.

of performance with new vs used chips. This lowers the cost per SNP to almost one-third of the cost of using a new microelectronic chip and more lowers the cost compared with RFLP analysis by more than one-half. This is approximately the same cost reported by others for detecting eight SNPs on one test site simultaneously (€1.62 per SNP) (6 ). It should be noted, however, that purchase of the Nanogen NMW 1000 Nanochip Molecular Biology Workstation is not included in these calculations. The microelectronic chip examined in this study was limited by the number of test sites per chip. Increasing the number of addressable sites per chip to 400 (7 ) would improve throughput. Until this is achieved, the microelectronic chip is potentially useful primarily when many SNPs can be detected on the same test site. This would minimize the cost per SNP and contribute to high throughput. Advantages compared with other microarray methods include the possibility of reusing chips and the flexibility, which allows each chip to be customized according to the relevant assay design. Although other DNA microarray systems can simultaneously detect many SNPs in one individual, genotyping is limited because of the need to use predefined sets of SNPs (5 ), the low accuracy of heterozygous samples (10 ), and the high cost. Fluorescence resonance energy transfer also has high-throughput capabilities but requires large amounts of DNA ( 50 ng) per SNP determination and lacks multiplexing ability compared with the microelectronic chip (11, 12). The TaqMan method, which also is capable of high throughput, has no intermediate processing, making the method highly automated compared with the microelectronic chip (13 ). Although mass spectrometry is a high-throughput genotyping system, it requires, like the microelectronic chip, high-purity samples for genotyping, thus increasing technician time and sampleprocessing costs (14, 15 ). In conclusion, we demonstrate that SNP detection by microelectronic chips is comparable to RFLP analysis in terms of throughput, accuracy, and cost-effectiveness, but the limitations of microchip analysis, such as the high purchase price and lower amenability to automation, must be kept in mind.