Hyperbilirubinemia in anicteric blood?

Plasma total bilirubin for a 65-year-old man was high [19.1 mg/dL (326 mol/L)] on a Roche cobas 6000 analyzer. However, the specimen was anicteric and the icteric index was 1 (approximately 1 mg/dL or 17 mol/L). A dilution study demonstrated nonlinear results. Direct bilirubin was measured as normal. The split specimen aliquots were further measured on analyzers from 5 different manufacturers (Table 1). The patient’s total protein and albumin were 93 and 34 g/L (reference intervals: 60 – 80 and 38 –50 g/L).