Stability was determined clinically by treating physicians and independent adjudication committee and by laboratory measures; (i) serum NCC using EDTA chelation (NCC-Ex) (ii) 24-h urinary Cu excretion (UCE) (iii) serum alanine aminotransferase (ALT) < 2x ULN. Conclusion: Clinician selected stable adults with WD on maintenance DPA showed wide variations in UCE and a proportion with lower-than-expected NCC; patterns suggesting possible under dosing/ poor adherence or possible over-treatment. Descriptive statistics of common laboratory measures used to determine clinical stability in adults with Wilson Disease (WD) Parameter (unit) N Mean SD Median Range (min, max) DPA dose (mg/kg) 76 13.7 4.7 13.1 4.4, 29.8 UCE (mcg/kg) 87 600.5 414.1 497 46.8, 2172 NCC-Ex (mcg/L) 79 57.8 24.03 54.8 13.1, 124 NCC-Sp (mcg/L) 77 56.6 26.0 56.6 16.2, 149 Cu (mcg/L) 84 298.1 232.2 224 54, 884.4 Ceruloplasmin (mg/L) 87 80.8 47.6 52 52, 240.2 ALT (U/L) 86 35.3 24.5 26.5 6, 110 AST (U/L) 86 25.9 10.1 24 12, 79 GGT (U/L) 87 47.7 65.1 27 10, 425 INR 86 1.06 0.16 1.03 0.76, 2.2 Bilirubin (mmol/L) 86 15.3 8.8 13.1 5.8, 58.4 Albumin (g/L) 87 43.4 3.3 44 35, 50 Creatinine (mmol/L) 87 73.4 14.8 72.9 44, 110.9 Urea Nitrogen (mmol/L) 87 5.5 1.7 5.1 2.7, 13.4 GFR (mL/min) 87 117.9 33.7 114 37, 213 Proteinuria (g/L) 87 71.2 4.7 72 55, 80 Hemoglobin (g/dL) 86 14.3 1.2 14.4 11.7, 16.8 Leucocytes (x109/L) 86 5.5 1.7 5.3 2.9, 12.1 Neutrophils (x109/L) 86 3.3 1.3 3.04 1.5, 8.4 Platelets (x109/L) 86 199 64.7 199 48, 362 Reference 1.