6572
Methods : This study included 1013 adult patients on HD who did not have a malignancy , liver cirrhosis , thalassemia , iron deficiency , gastrointestinal bleeding , or a major operation within 6 months .
 iron
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 iron