Na 160 mmol/L, K+ 6.8 mmol/L, Ca 1.5 mmol/L, Fe 4 µmol/L. What happened?

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Multiple Choice

Na 160 mmol/L, K+ 6.8 mmol/L, Ca 1.5 mmol/L, Fe 4 µmol/L. What happened?

The main idea is that this pattern of results points to EDTA contamination. EDTA in collection tubes contains a potassium salt and is a strong chelator of divalent cations. If EDTA from a tube contaminates the serum or plasma, potassium is falsely elevated because you’re adding extra potassium from the EDTA salt, while calcium (and other divalent metals like iron) is falsely reduced because EDTA binds them. Here, the markedly high potassium (6.8) alongside a low calcium (1.5) and low iron (4) fits that contamination picture. The scenario described by the option implies improper draw order or carryover from an EDTA tube into the sample, which explains the artifact. The other explanations don’t produce this specific combination of electrolyte changes: hemolysis would raise potassium but not cause such a consistent drop in calcium and iron, and wrong patient ID or calibrator mislabeling wouldn’t generate this characteristic pattern of results.

The main idea is that this pattern of results points to EDTA contamination. EDTA in collection tubes contains a potassium salt and is a strong chelator of divalent cations. If EDTA from a tube contaminates the serum or plasma, potassium is falsely elevated because you’re adding extra potassium from the EDTA salt, while calcium (and other divalent metals like iron) is falsely reduced because EDTA binds them.

Here, the markedly high potassium (6.8) alongside a low calcium (1.5) and low iron (4) fits that contamination picture. The scenario described by the option implies improper draw order or carryover from an EDTA tube into the sample, which explains the artifact. The other explanations don’t produce this specific combination of electrolyte changes: hemolysis would raise potassium but not cause such a consistent drop in calcium and iron, and wrong patient ID or calibrator mislabeling wouldn’t generate this characteristic pattern of results.

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