LDL phenotype is an outdated designation to identify a large LDL type from a small LDL type. LDL phenotype was used in the past because accurate data on individual LDL subgroups was not available or inaccurate. Today the LPP™ test gives accurate information on large-buoyant and small-dense LDL subgroups and this is much more specific for treatment and risk assessment than phenotype.
Phenotype is one result that represents an average density or size for all LDL subgroups and is useful if the value of LDL is high but is very misleading if LDL is low. In fact when LDL is low or reduced in treatment the end result is often a more smalldense LDL profile with a type B phenotype. Therapy such as statin drugs remove mostly large-buoyant LDL leaving the treated patient with a much reduced LDL particle number that is comprised of a higher percentage of small-dense LDL. Since overall particle numbers are reduced this is a positive result for the patient.
A better method for LDL risk assessment and treatment is to use the number of LDL III and IV particles as a guide. These values give the exact number of type B or the most atherogenic LDL particles regardless of the phenotype designation.
The qualitative phenotype result can be determined in an alternate way rather than from the mean LDL density by looking at the dense LDL III and LDL IV subgroups. If both LDL III and LDL IV are “normal” then the phenotype is “Type A”. If one or both LDL III or LDL IV is “borderline” then the phenotype is “Type I” and if one or both LDL III or LDL IV is “high” then the phenotype is “Type B”.