Thesis

38 Chapter 2 Comparison of DNA methylation analysis in different urine fractions Subsequently, the DNA methylation levels of GHSR, SST, and ZIC1 were compared among paired urine fractions to determine the correlation between the different urine components. For all markers, a strong to very strong (r ≥ 0.77 – 0.92) correlation was found between different urine fractions of women with EC (Table 3). Table 3: Correlation of methylation markers between paired urine fractions from EC patients (n = 40). Full void urine versus urine sediment Full void urine versus urine supernatant Urine sediment versus urine supernatant GHSR 0.85 0.92 0.89 SST 0.78 0.91 0.74 ZIC1 0.87 0.90 0.77 EC: endometrial cancer. Spearman’s rank correlation coefficient (r) was calculated based on the log2-transformed Cq ratio’s. r = 0.40 − 0.59 moderate correlation, r = 0.60 − 0.79 strong correlation, r = 0.80 − 1.00 very strong correlation. DNA methylation as diagnostic marker for EC detection in each urine fraction All DNA methylation markers showed highly increased methylation levels in patients as compared to controls, resulting in p values < 0.001 for GHSR and ZIC1 in all urine fractions, and for SST in full void urine and urine supernatant (Figure 1). The diagnostic potential of each urine fraction was determined by computing ROC curves (Supplementary Figure 1) and quantifying AUCs of all markers (Table 4). Full void urine samples showed the highest discriminatory power for distinguishing patients from controls, with AUCs of 0.95, 0.92, and 0.86 for GHSR, SST, and ZIC1, respectively. Table 4: The AUC (95%-CI) of GHSR, SST and ZIC1 in urine fractions for EC detection. Full void urine Urine sediment Urine supernatant GHSR 0.95 (0.90 − 1.00) 0.89 (0.81 − 0.96) 0.92 (0.86 − 0.98) SST 0.92 (0.86 − 0.98) 0.65 (0.53 − 0.76) 0.76 (0.65 − 0.87) ZIC1 0.86 (0.77 − 0.94) 0.76 (0.66 − 0.87) 0.84 (0.74 − 0.93) AUC: area under the ROC curve; 95%-CI: 95% confidence interval; EC: endometrial cancer.

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