The overall intra-variation was 2.5% (range: 0.8-6.8% (median: 1.9%)) (N = 16) for the MMP-9:TIMP-1 measurements in breast cancer plasma, while the inter-variation between plates was 19.9% (range: 11.3-29.2% (median: 19.6%)) (N = 16). The gene discussed is TIMP1; the disease is breast cancer.