5 April 2015 (Sunday) - What *Are* We Measuring?

Here’s an article which made me think.


The IFCC Working Group for the Standardization of Cardiac Troponin I (WG-TNI) believes it is possible to standardize cTnI measurement and has evaluated 16 current assays for measurement equivalence and their standardization capability using an initial harmonization approach. At the same time serum pools prepared in various ways from cTnI-positive patient sera were tested for harmonization. 

Results of the pilot study showed about a 10-fold difference in cTnI concentrations among assays and that this is largely due to differences in calibration. When these calibration differences were removed by a mathematical recalculation (using regression slope and y-intercept values), the inter-assay variation is typical of External Quality Assessment Scheme results of methods measuring more common analytes.

Blah blah blah…. Or so I thought until I read the next bit

The ability to mathematically recalibrate assays is an indication that the assays are measuring the same analyte despite the diversity of cTnI antibodies in use and the inherent structural variability of the cTnI analyte. 

That’s rather important. For all that we come up with these numbers in the lab and the controls we use say we’ve got the right number, can we *really* be sure what we’re coming up with?

Apparently so.

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