text: Lyophilized receptor-positive tissue powders, yo
  Cytosols from calf uterus and human breast tumor tissue, yo
  Assessin' the validity of them routine dextran-coated charcoal estrogen receptor assays, yo
  
  Since '78, lyophilized reference preparations been analyzed, yo
  Twice a year by 18 laboratories in the Netherlands, yo
  Eight trials back to back, twenty samples in the mix, yo
  Inter-laboratory variability of estrogen receptor results, you know
  
  It decreased over time, that's a fact, yo
  Most labs found receptor values 'round the median, yo
  But some be consistently higher or lower, showin' difference, yo
  The variability between labs, let me give you the lowdown, yo
  
  Cytosol dilution, non-specific binding determination, yo
  Concentration and volume of dextran-coated charcoal, yo
  Single dose assays or Scatchard analysis, yo
  All play a role in the variability, that's how it goes, yo
  
  Now let's talk about the presence or absence, yo
  Of them estrogen receptors, gotta know, yo
  Over 98% agreement for lyophilized reference samples, yo
  With high receptor content, they know what's up, yo
  
  But for samples with low receptor content, listen up, yo
  85% agreement, that's what they found, yo
  And 12% of assays on receptor-negative material, yo
  Reported estrogen receptor-positive, that's real, yo
  
  Now the protein results, let's dive in, yo
  Using Coomassie Brilliant Blue for determination, yo
  And human serum albumin standard in the mix, yo
  Decreased variation coefficient to 7.5%, that's slick, yo