MSU reference range changed for IGF-1 (and paper)

[Wendy&Neko]

One of our members just got IGF-1 results back from MSU, with the following note on the results:

Reference Range: 61 - 916 ng/mL
Insulin-like Growth Factor 1 (CLIA):
Effective January 25th, 2024, the insulin-like growth factor 1 (IGF-1) assay methodology changed from a radioimmunoassay (RIA) to a chemiluminescent assay
(CLIA). The reported units changed from nmol/L to ng/mL

This puts MSU in line with RVC in types of units used. Their upper end for normal IGF-1 may be different.

The following paper talks about the change in assay type, which should hopefully make it cheaper and more available than just MSU and RVC.
Method Validation and Establishment of Reference Intervals for an Insulin-like Growth Factor-1 Chemiluminescent Immunoassay in Cats

Some interesting notes from this article:

• The new assay is the same as used for humans, hence more available, and doesn't need the extra testing conditions of a radioimmunoassay. The paper suggested the major vet labs can now do the test. And at a reduced price.
• "Future studies are needed to assess the effect of age on IGF-1 concentration in cats covering a wider age interval than in our study." Small sample size studies showed higher IGF-1 concentrations in younger cats. In humans, there are reference ranges for different age groups.
• Similarly, the small study showed higher IGF-1 concentrations in heavier cats so more study needed to determine how weight plays in reference ranges. This may or may not be breed specific.
• The study used a reference range upper end of 746 for normal vs the 916 now used by MSU. At least some of the authors are at RVC, so we may see different results from the two labs.