A gold top tube shows extreme hyperkalemia, hypocalcemia, hypomagnesemia, and very low ALP in a patient with no distress. What is a possible cause?

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The main idea is that this pattern comes from a lab artifact caused by EDTA contamination. If an EDTA-containing tube is drawn after a serum (gold) tube, trace EDTA can carry over into the serum sample. EDTA is a strong chelator of divalent cations and also brings in potassium. That means it binds calcium and magnesium, making their measured levels falsely low, and it adds potassium, making the potassium reading falsely high. EDTA also chelates metals needed for alkaline phosphatase activity, so ALP can appear very low. Taken together, extreme hyperkalemia with hypocalcemia, hypomagnesemia, and very low ALP in a patient who isn’t acutely ill points to EDTA carryover rather than a true disorder.

Other possibilities don’t fit this coherent pattern: a genuine electrolyte disorder wouldn’t usually present with this exact combination in an asymptomatic patient, a faulty analyzer would not reliably reproduce this specific EDTA-related pattern, and improper storage of the gold top tube wouldn’t produce the same concrete electrolyte and enzyme changes caused by EDTA contamination.