We found that mitochondrial ROS generation in PBMCs, but not urinary 8-OHdG, was linked to plasma BNP levels in CHF patients, suggesting that mitochondrial ROS generation in circulating PBMCs may directly reflect the disease severity of HF rather than urinary 8-OHdG, a non-specific biomarker of oxidative damage. The gene discussed is NPPB; the disease is hydrops fetalis.