Receiver-operating characteristic curve analysis revealed venous MPO and NT-proANP (area under the curve [AUC] 0.755, 95% CI 0.599–0.912, P = .010; and AUC 0.752, 95% CI 0.551–0.953, P = .011) as acceptable predictors for intermediate AF recurrence, whereas matrix metalloproteinase-2, intercellular adhesion molecule-1, and established cardiovascular biomarkers such as N-terminal pro–B-type natriuretic peptide, troponin T, and C-reactive protein were not (all AUC <0.600). The gene discussed is MPO; the disease is atrial fibrillation.