| Validation sample | 
  Bias | 
  Within-run precision (n=3) | 
  Between-run precision (n=3) | 
    
   
  | 2 pmol/106 cells | 
  11.7% | 
  11.0% | 
  Negligible | 
    
   
  | 20 pmol/106 cells | 
  4.5% | 
  6.2% | 
  Negligible | 
    
   
  | 200 pmol/106 cells | 
  −6.4% | 
  16.2% | 
  Negligible | 
    
  
 Negligible, smaller value than the Within-run precision |