Patent Document ID: 9367663
Application ID: 13669136
Patent Flag: 1

Claim One:
1. A method for determining presence or absence of a chromosome trisomy for a test sample, comprising: (a) obtaining counts of sequence reads mapped to portions of a reference genome, which sequence reads are of circulating cell-free nucleic acid from a test sample from a pregnant female; (b) determining a guanine and cytosine (GC) bias coefficient for the test sample based on a fitted relation between (i) the counts of the sequence reads mapped to each of the portions and (ii) GC content for each of the portions; wherein the GC bias coefficient is a slope for a linear fitted relation; (c) determining a genomic section level for each of the portions based on the counts of (a), the GC bias coefficient of (b) and a fitted relation, for each of the portions, between (i) the GC bias coefficient for each of multiple samples and (ii) the counts of the sequence reads mapped to each of the portions for the multiple samples, thereby providing calculated genomic section levels; and (d) determining presence or absence of a chromosome trisomy for the test sample according to the calculated genomic section levels.