Fig. 2

Levey-Jennings chart-based IQC for aneuploid detection. In Levey-Jennings charts (Fig. 2a) and (Fig.2b), quality-control data are plotted in the form of a graph in which time (dates) is represented on the x-axis and the numerical value (concentration/ratio) of the quality-control test is represented on the y-axis. The charts contain several reference lines including one reference line for the mean (\( \overline{\mathrm{X}\ } \)) and three reference lines on either side of the mean, representing standard deviation limits (1 SD, 2 SD, and 3SD). For quality-control cells (a), the values of \( \overline{\mathrm{X}\ } \), \( \overline{\mathrm{X}\ } \) ±1 SD, \( \overline{\mathrm{X}\ } \) ±2 SD, and \( \overline{\mathrm{X}\ } \) ±3 SD of trisomy 13 (\( \overline{\mathrm{X}\ } \) =10.2, SD = 1.7) and 21 (\( \overline{\mathrm{X}\ } \) =90.3, SD = 2.3) analyzed 20 times were plotted on the y-axis in Levey-Jennings charts (Fig. 2a) and (Fig. 2b), respectively. Then, the quality-control cells (a) and clinical samples were analyzed under the same experimental conditions and the results of each analysis of trisomy 13 were plotted in Levey-Jennings chart (Fig. 2a) to construct Levey-Jennings chart-based IQC for trisomy 13 (Fig. 2c, the values for the 5th and 6th exceeded \( \overline{\mathrm{X}\ } \) + 2 SD), and the results of trisomy 21 were plotted in Levey-Jennings chart (Fig. 2b) to construct Levey-Jennings chart-based IQC for trisomy 21 (Fig. 2d, the values for 9th exceeded \( \overline{\mathrm{X}\ } \) ±3 SD)