I want to know whether insulin resistance can be quantified. If so, does this quantification allow us to compare different individuals? Does it allow us to compare insulin resistance in one individual at different moments in time or under different circumstances? What sort of clinical test/exam/measurement is necessary?
InsulinNation gives a good overview:
Pre-diabetes can exist for a long time in your body without triggering the most common outward signs of diabetes (continual thirst, frequent urination, blurred vision, etc). And standard methods of detecting insulin resistance or pre-diabetes using glucose tolerance tests or an A1C percentage often show false negatives; that’s because the pancreas is still able to produce enough insulin to overcome insulin resistance. Type 2 diabetes is also good at hiding itself; it is common that someone diagnosed as a Type 2 has already had the disease for five years, which makes the battle for control an uphill climb even before it begins.
Fortunately, there are other ways to identify insulin resistance using biomarkers in blood drawn from patients as a normal part of an annual or semi-annual general checkup. These biomarker data can be plotted against what is considered normal, and as a result, place the person at a specific point along the path to pre-diabetes or to Type 2 diabetes itself.
Tools to detect insulin resistance include
Tests showing the degree of pancreatic output and what could be defined as “pancreatic stress”. These include both fasting insulin and fasting glucose, a Homeostasis Model Assessment (HOMA) that measures beta cell function and insulin sensitivity, a C-Peptide test and a pro-insulin test;
Measurements of lipid hormones such as leptin and adiponectin. These biomarkers can give insight into a person’s unique communication between fat metabolism and insulin.
Tests that evaluate a person’s degree of inflammation.These biomarkers include a cardiac-specific C-reactive protein measurement (CRP) and a sedimentation rate.
Measurements that quantify fatty acid metabolism and the fatty acids released by the patient. These can also give particle size and number as well as an average inflammatory number.
There is a surrogate marker of insulin resistance, called IGFBP-1. It's a blood test. This test is done at a specialty lab and takes several weeks for the results to come back. You get your blood draw in the usual place (e.g. your local hospital), but then the sample is sent out to a specialty lab. This is a relatively non-invasive test. You can put EMLA cream on the inside of a child's elbow and there will be no pain for the blood draw.
An individual with insulin resistance can do this test between once and four times a year, to track progress (or lack thereof). The lower the result, the more insulin resistant you are. For example, my son, who has been diagnosed with insulin resistance, has varied between 4 and 20 (I forget what the units are). When he was at 4, we were seeing more symptoms and higher BMI for age. When he was at 16 things were better. At 20, better still. I'm afraid I'm not certain what range is considered normal -- but I vaguely remember 20 and above was good.
There are a number of articles out there about this. Here's one: Maclaren NK, Gujral S, Ten S & Motagheti R. Childhood obesity and insulin resistance. Cell Biochemistry and Biophysics 2007 ;48:73–78.