Roger, are the HDLc and LDLc both direct assays by both labs? 

 

Once upon a time, I did a contract study for an IVD manufacturer looking for biases between 1st generation and 2nd generation assays for HDLc and LDLc.  Since the reported discordant samples were rare, I ran these 4 assays on hundreds of samples, from in patients and out patients, submitted to the university hospital lab, regardless of diagnosis or acuity.  During this study I found a few samples that had undetectable HDLc and LDLc by either generation of assay.  As interesting as that was, these were not discordant samples that I was seeking, and I only had time for a cursory check of their condition.  The only thing I noticed was that they were experiencing major acute phase response.  Perhaps CRP or other acute phase reactants can cause negative interference in some of the direct assays.

 

-Jim