Advancing NGS quality control to enable measurement of actionable mutations in circulating tumor DNA.

The primary objective of the FDA-led Sequencing and Quality Control Phase 2 (SEQC2) project is to develop standard analysis protocols and quality control metrics for use in DNA testing to enhance scientific research and precision medicine. This study reports a targeted next-generation sequencing (NGS) method that will enable more accurate detection of actionable mutations in circulating tumor DNA (ctDNA) clinical specimens. To accomplish this, a synthetic internal standard spike-in was designed for each actionable mutation target, suitable for use in NGS following hybrid capture enrichment and unique molecular index (UMI) or non-UMI library preparation. When mixed with contrived ctDNA reference samples, internal standards enabled calculation of technical error rate, limit of blank, and limit of detection for each variant at each nucleotide position in each sample. True-positive mutations with variant allele fraction too low for detection by current practice were detected with this method, thereby increasing sensitivity.

Evaluation of DNA microarray results with quantitative gene expression platforms.

We have evaluated the performance characteristics of three quantitative gene expression technologies and correlated their expression measurements to those of five commercial microarray platforms, based on the MicroArray Quality Control (MAQC) data set. The limit of detection, assay range, precision, accuracy and fold-change correlations were assessed for 997 TaqMan Gene Expression Assays, 205 Standardized RT (Sta)RT-PCR assays and 244 QuantiGene assays. TaqMan is a registered trademark of Roche Molecular Systems, Inc. We observed high correlation between quantitative gene expression values and microarray platform results and found few discordant measurements among all platforms. The main cause of variability was differences in probe sequence and thus target location. A second source of variability was the limited and variable sensitivity of the different microarray platforms for detecting weakly expressed genes, which affected interplatform and intersite reproducibility of differentially expressed genes. From this analysis, we conclude that the MAQC microarray data set has been validated by alternative quantitative gene expression platforms thus supporting the use of microarray platforms for the quantitative characterization of gene expression.

New Tool for Monitoring Molecular Response in Patients With Chronic Myeloid Leukemia.

OBJECTIVE: Chronic myeloid leukemia treatment monitoring using polymerase chain reaction-based peripheral blood testing of t9;22 BCR-ABL1 provides improved test sensitivity over cytology but suffers from inadequate standardization in most laboratories due to variations inherent in the existing polymerase chain reaction methodologies. We performed the initial analytic performance evaluation of a novel competitive template-based peripheral blood b2a2/b3a2 transcript abundance method, called standardized nucleic acid quantification (SNAQ) test, with hypothesis that this will produced more consistent results with less frequent interlaboratory variations. MATERIALS AND METHODS: Thirty-six chronic myeloid leukemia patients treated at our institution were enrolled. We compared SNAQ test with 2 laboratory developed test at the MD Anderson molecular diagnostic laboratory and Cancer Genetics Institute for analyzing BCR-ABL1 from peripheral blood samples. Each test result (n=36) was ranked against all the other samples tested by the same method. RESULTS: The Pearson correlation between SNAQ and laboratory developed test done at 2 labs was met by correlations of 0.97, 0.96, 0.96, and 0.94. Analysis of variance of log %BCR-ABL1 interlaboratory results indicated no significant difference (P=0.98). Post hoc analysis of method agreement showed the SNAQ method had a 95% limit of agreement of ±3-fold between laboratories. CONCLUSIONS: In this pilot study, SNAQ methodology performed consistent with half-log accuracy. Additional studies from a larger sample size and correlation with clinical outcomes are required to confirm this observation.

Quality-controlled measurement methods for quantification of variations in transcript abundance in whole blood samples from healthy volunteers.

BACKGROUND: Transcript abundance (TA) measurement in whole blood frequently is conducted to identify potential biomarkers for disease risk and to predict or monitor drug response. Potential biomarkers discovered in this way must be validated by quantitative technology. In this study we assessed the use of standardized reverse transcription PCR (StaRT-PCR) to validate potential biomarkers discovered through whole blood TA profiling. METHODS: For each of 15 healthy volunteers, 6 blood samples were obtained, including 3 samples at each of 2 separate visits. Total variation in TA for each gene was partitioned into replicate, sample, visit, study participant, and residual components. RESULTS: Variation originating from technical processing was <5% of total combined variation and was primarily preanalytical. Interindividual biological sample variation was larger than technical variation. For 12 of 19 tests, the distribution of measured values was gaussian (Shapiro-Wilks test). CONCLUSION: For control or diseased population groups with variation rates as low as those observed in this control group, 17 individuals per group would be required to detect 1 SD change with 80% power with a 2-sided alpha = 0.05 statistical test for mean differences.