Factitious methemoglobinemia caused by hyperlipemia

Area of Science:

• Clinical Chemistry
• Hematology
• Critical Care Medicine

Background:

• Accurate blood gas analysis is crucial for managing critically ill patients.
• Hyperlipemia, common in conditions like diabetic ketoacidosis, can pose analytical challenges.
• Automated spectrophotometry is widely used for blood gas and hemoglobin measurements.

Observation:

• A patient with diabetic ketoacidosis, alcoholism, and pancreatitis presented with severe hyperlipemia.
• Automated spectrophotometry yielded falsely elevated methemoglobin and hemoglobin levels, and low oxygen saturation.
• In vitro studies confirmed that high triglyceride levels (≥500 mg/100 ml) caused erroneous results.

Findings:

• Hyperlipemia significantly interferes with spectrophotometric measurement of methemoglobin, total hemoglobin, and oxygen saturation.
• Lipid interference led to falsely elevated methemoglobin (19%) and hemoglobin, with "negative" carboxyhemoglobin values.
• Washing erythrocytes to remove excess lipids corrected the analytical abnormalities.

Implications:

• Clinicians should be aware of potential analytical interferences from hyperlipemia in blood gas testing.
• Consider lipid removal techniques or alternative assays when severe hyperlipemia is present.
• This highlights the importance of sample quality assessment in laboratory diagnostics for critical care.