497
In order to study the influence of iron overload on the polymorphonuclear leucocyte ( PMN ) metabolism of patients on chronic hemodialysis , generation of superoxide anion ( O2 - ) by PMN in whole blood was compared in two groups of hemodialyzed patients : group A consisted of twenty - one individuals with serum ferritin levels above 1000 ng / ml and group B of nineteen individuals with serum ferritin levels below 1000 ng / ml .
 GENE: ferritin; GENE: ferritin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: ferritin; GENE: ferritin