Sometimes I see references to the amount of prolamin or gliadin instead of gluten, why?

The following labs have excellent reputations for such tests:
Specialty Labs
2211 Michigan Ave.
Santa Monica California 90404
Tel: 310 828-6543 or 800 421-4449
Internet: Open Original Shared Link
The University of Maryland at Baltimore
Attention: Karoly Horvath, MD, or Athba Hammed, Research Assistant
School of Medicine
Division of Pediatric Gastroenterology and Nutrition Laboratory
UMAB/Bressler Research Building, Room 10-047
655 West Baltimore Street
Baltimore, MD, 21201
410 706-1997 or fax at 410 328-1072
University of Iowa Foundation for Celiac Disease Research
University of Iowa Hospitals and Clinics
200 Hawkins Drive
Iowa City, IA 52242
IMMCO Diagnostics, Inc.
Vijay Kumar, Ph.D.
IMMCO Diagnostics...

For 100 units of whole grain wheat, about 70 units of white flour results from the milling process. The rest is separately sold as wheat bran or wheat germ. Those 70 units of flour are about 10%- 15% protein, thus about 7 to 10 units of protein for 100 units of whole wheat. The protein is about 80% gluten, thus about 6 to 8 units of gluten for 100 units of whole wheat. Since one typically sees wheat flour as an ingredient, applying the 70% factor implies 8 to 12 units of gluten per 100 units of wheat flour.

Most of the wheat grain and of white flour is made up of starch granules. Starch granules make up about 75% of grain or of white flour. In the processes used to make wheat starch, a small amount of the gluten protein (actually mostly the gliadin fraction, but not entirely), sticks to the surface of the starch granules. The amount depends on the washing method, how many times the granules are washed, and factors like that. Wheat starch can be made very low in surface protein and it is only the surface protein that is of concern (there are some internal granule proteins, but we are pretty sure that they are not gluten proteins).
For more information on Codex wheat starch visit the Open Original Shared Link page.

The average gluten-containing diet contains roughly 10-40 grams of gluten per day. This figure is based on the amounts of gluten in your average slice of whole wheat bread, which contains around 4.8 grams of gluten (10% gluten by weight), and the amount of gluten in a serving of pasta, which is roughly 6.4 grams of gluten (11% gluten by weight). The smallest amount of gluten which has been shown by a biopsy to cause damage to a celiac is 0.1 gram per day (Catassi et al.). This is approximately the amount of gluten contained in 1/48th of a slice of bread! The biopsies in this study showed an increase in intraepithelial lymphocyte count, one of the earliest signs of damage. The challenge was on 10 patients (children) for 28 days each. Four of the patients showed an increase in IgA...