[BioC] Ways to verify identity samples

[=?big5?B?qLlAeXp1?=]

Hi all:
I have 11 Human Genome U133 plus 2.0 samples.
There are 2 of them are identity samples.
I try to use correlation of samples to verify them.
But even not identity samples have high correlations.

here is my test code
#read all 11 samples expression value table , (using MAS5)
sample <- read.table("samples.txt",sep="\t")
corelation <- cor(sample,sample,method="pearson")

Could any one have any other ways to verify identity samples ?

Sincerely,
Chang Bang