SAQC (SNP Array Quality Control)


[Introduction:] SAQC software is written in R and R-GUI and was developed as a user-friendly tool for the visualization and evaluation of data quality of genome-wide SNP arrays.


[Background:] Genome-wide single-nucleotide polymorphism (SNP) arrays containing hundreds of thousands of SNPs from the human genome have proven useful for studying important human genome questions. Data quality of SNP arrays plays a key role in the accuracy and precision of downstream data analyses. However, good indices for assessing data quality of SNP arrays have not yet been developed.


[Results:] We developed new quality indices to measure the quality of SNP arrays and/or DNA samples and investigated their statistical properties. The indices quantify a departure of estimated individual-level allele frequencies (AFs) from expected frequencies via Mahalanobis distances. The proposed quality indices followed lognormal distributions in several large genomic studies that we empirically evaluated. AF reference data and quality index reference data for different SNP array platforms were established based on samples from various reference populations. Furthermore, a confidence interval method based on the underlying empirical distributions of quality indices was developed to identify poor-quality SNP arrays or DNA samples. Analyses of authentic biological data and simulated data show that this new method is sensitive and specific for the detection of poor-quality SNP arrays and/or DNA samples.


[Conclusions:] This study introduces new quality indices, establishes references for AFs and quality indices, and develops a detection method for poor-quality SNP arrays and/or DNA samples. We have developed a new computer program that utilizes these methods called SNP Array Quality Control (SAQC). The program is available online (Welcome to the SAQC website).


If your results are published based on the use of SAQC, please cite the following reference:


Hsin-Chou Yang*, Hsin-Chi Lin, Meijyh Kang, Chun-Houh Chen, Chien-Wei Lin, Ling-Hui Li, Jer-Yuarn Wu, Yuan-Tsong Chen, and Wen-Harn Pan (2011). SAQC: SNP array quality control. BMC Bioinformatics 12, 100. (


*Correspondence: Hsin-Chou Yang, Institute of Statistical Science, Academia Sinica, 128, Academia Road, Section 2 Nankang, Taipei 115, Taiwan. (Fax) 886-2-27831523; (Tel) 886-2-27889311 ext. 113; (E-mail) 



l   Software downloading:






SAQC 1.0



139  MB


SAQC 2.1



559  MB


* SAQC provides multiple databases and test examples. Therefore, the file is somewhat large!

l   R and R-GUI downloading: R language (Version 2.11.1) and Tcltk2 [date: 2010/09/10]