4-12 mcg/mL Critical value: >12 mcg/mL

Criterion: recovery plus or minus 0.5 ug/mL of initial value at concentrations less than 5 ug/mL or plus or minus 10% of initial value at concentrations greater than 5 ug/mL. Icterus: No significant interference from bilirubin up to an I index of 60 (approximate bilirubin concentration: 60 mg/dL). Hemolysis: No significant interference from hemoglobin up to an H index of 1000 (approximate hemoglobin concentration: 1000 mg/dL). Lipemia: No significant interference from triglycerides up to 1000 mg/dL. No significant interference from total protein up to 12 g/dL or rheumatoid factor up to 180 IU/mL. The incidence of patients with antibodies to E. coli beta-galactosidase is extremely low. However, some samples containing such antibodies can result in artificially high carbamazepine results that do not fit the clinical profile. As with any assay employing mouse antibodies, the possibility exists for interference by human anti-mouse antibodies (HAMA) in the sample, which could cause falsely elevated results.