Using HP1BP3 and TTC9B pyrosequencing values in the prediction linear discriminant model, we obtained an AUC of 0.87 for the prepartum euthymic sample, which included three additional women not assessed via microarray (PPD N=13, non-PPD N=22). AUC values did not vary significantly when determined for blood collected in each trimester separately (AUC 1st=0.86, AUC 2nd=0.80, AUC 3rd=1). We next evaluated the performance of the biomarker loci on blood taken from the prepartum depressed sample. While the relative direction of TTC9B association with PPD status was similar to the prepartum euthymic women, it was not significantly different (Figure 2h and Table 2). For HP1BP3 the direction of association was significant but in the opposite direction to that observed in the prepartum euthymic cohort (Figure 2d and Table 2). Linear discriminant model prediction of PPD status in this cohort returned an AUC of 0.12, which represents an 88% prediction accuracy of PPD status in the reverse direction.
