Table 3. Comparison of apo B immunoturbidometric assay/immunonephelometric assay and NMR–LDL-P methodologies.
Assay methodsMultiple vendors, not all standardizedProprietary in-house, not standardized
CalibrationReference material (SP3–07, SP3–08), performed by end user using kit calibratorsNot calibrated; uses proprietary library of isolated lipoprotein fractions to set concentrations
Entity measuredAntigen–antibody complexTerminal methyl groups on lipoprotein-associated lipids
Precision, within assay (%CV)Lab dependent2%–4%
Precision, between assay (%CV)Lab dependent, CV 4.1%–11.6%2%–4%
Precision, mean within method, between laboratory (%CV)Lab dependent, 7.2% (CAP PTa data)NA
Fed or fastedEitherEither
Samples frozen at −70 °CStable for yearsStable for years
Stability in ongoing clinical studiesCan change over time, depends on manufacturer diligenceProbably stable over time, requires internal surveillance
Information reportedapo B concentrationParticle number and size, lipid concentrations
Standardization programYes, performed by manufacturerNo
Performance criteriaNoneNone
Potential problemsAntibody recognition of epitopes on variant LDLs, e.g. small, complex formation rate, turbidity vs detergent effect, may include VLDL, IDL, and Lp(a)Identifies particle only by size, i.e., includes IDL and Lp(a) in LDL-P
Availability of testRuns in typical clinical lab on common instrumentationRun only at LipoScience on specialized instrumentation
GrowthReadily scalable; numerous vendors and applications for most analyzersLimited by capacity of central lab
CostModest (≅$17)Modest to high (≅$30–$40)
  • a CAP PT, College of American Pathologists Proficiency Testing Program; NA, not applicable or available.