A 42-year-old man was under regular outpatient review following a renal transplant. Renal function was impaired with a plasma creatinine of 150 µmol/l (normal range 60–125). A full blood count, performed on a Sysmex XE-2100 automated instrument, showed normal white cell and platelet counts and apparently a mild anemia with a hemoglobin concentration (Hb) of 126 g/l. The mean cell hemoglobin concentration (MCHC) was increased to 367 g/l (316–349), and a blood film was therefore examined. This did not show spherocytes, irregularly contracted cells or any other erythrocyte abnormality known to increase the MCHC. However the red cells had fuzzy outlines (image). This raised the suspicion of hyperlipidemia. Triglyceride concentration was found to be 26.76 mmol/l (normal range 0–2).

The presence of fuzzy red cell outlines is the result of lipid interfering with the fixation and staining of the film; this finding is often dismissed as a ‘poor film' rather than being recognized as an abnormality that should be noted. It is, however, significant for two reasons. It alerts the laboratory to factitious results. The Hb is artefactually elevated as a result of turbidity and this leads to a factitious increase in the MCHC. This morphological observation can also lead to the detection of previously undiagnosed hyperlipidemia.