Multilayer-film analysis for urea nitrogen in blood, serum, or plasma.

Two types of multilayer-film slides for measurement of urea nitrogen in blood are reported here: one for whole-blood samples, the other for plasma or serum. Urea nitrogen concentrations in plasma are determined almost immediately, without preparation of reagents or centrifugation of blood samples. Because the sample volume applied to the slide is not critical, reliable results are quickly obtained by the neophyte.