An 86-year-old woman underwent hysterectomy for endometrial adenocarcinoma. A blood sample for routine laboratory testing was drawn into a lithium heparin tube 1.5 h after surgery. After centrifugation, the plasma sample appeared green in color (Fig. 1). The patient had no specific diet or medications that might have accounted for the color change. 

Fig. 1. The patient's blood after centrifugation.


  1. What caused this change in plasma color?
  2. What other conditions could cause blood discoloration?
  3. Are there any safety concerns or possible interference with laboratory tests?
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