Drug-induced plasma discolouration mimicking icterus risks inappropriate withholding of critical lactate

A lactate concentration ≥4 mmol/L is associated with organ dysfunction and poor outcomes in sepsis, making accurate measurement and timely communication of critical results vital. Photometric lactate assays are common but prone to spectral interference from icterus, and objective assessment of haemolysis/icterus/lipaemia indices is essential to prevent release of compromised results. The authors report a patient with severely elevated lactate (10.2 mmol/L) in fluoride-oxalate plasma. The specimen was run on a colourimetric lactate oxidase method (Beckman Coulter AU5800 analyser at Cork University Hospital (CUH)). Since icteric indices were not routinely determined for fluoride-oxalate specimens, the sample was assessed by eye to be grossly icteric, and the initial decision was to withhold the lactate result per manufacturer guidelines. On review by the Consultant Clinical Biochemist, an automated icteric index was requested, which yielded a 1+ flag, corresponding with a total bilirubin in the range 42.7-85.5 μmol/L, and inconsistent with gross icterus. Review of the patient history indicated aplastic anaemia. Drug-related discolouration of the sample was suspected, and the haematology team confirmed eltrombopag therapy. The lactate result and subsequent reports were released with advisory comments, noting that the degree of any eltrombopag-related analytical interference was uncertain. This case demonstrates how a combination of drug-induced plasma discolouration, reliance on visual assessment of icterus, and inconsistent application of HIL indices across specimen types jeopardises the release of critical lactate results. Standardised automated index testing, clear protocols for interference evaluation, and timely multidisciplinary discussion of medication history are important safeguards in clinical laboratory practice.