sentences:  A standardized international reference material has been developed and is accepted by the WHO Expert Committee on Biological Standardization and the International Federation of Clinical Chemistry and Laboratory Medicine.Although further standardization is still needed, development of a reference material is an importance step toward standardizing results.Lipoprotein(a) - Lp(a)
  
  Lp(a) appears with different isoforms (per kringle repeats) of apolipoprotein; 40% of the variation in Lp(a) levels when measured in mg/dl can be attributed to different isoforms.