Specific determination of plasma and urinary lactose.

The recognition of three cases of lactose intolerance in the Sheffield Children's Hospital led to an investigation into the specific determination of plasma and urinary lactose levels following lactose loading tests. Using the method of Reithel (1962) (see below) it was found that aqueous solutions of lactose (0.1 ml.) were readily and consistently determined even at levels down to 5 mg. per 100 ml. As plasma glucose interferes with the determination it was destroyed by glucose oxidase and the oxidase itself was removed during the subsequent deproteinization.