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Dry, thin films containing all necessary reagents for clinical analysis by colorimetry have been designed. Reagents in a matrix of hydrophilic polymer are coated on top of a transparent plastic base. A white isotropically porous polymer spreading layer, 80% void volume, is coated over the reagent layer(s). In the analysis, a drop (typically 10 microliter) of undiluted serum or other fluid is touched to the spreading layer. The fluid spreads rapidly and uniformly through the pore structure, filling a void volume corresponding to the drop volume. Water and low-molecular-weight components diffuse from the spreading layer into the reagent layer(s), initiating the reaction sequence. The spreading layer acts also as a white optical diffuser for reflection densitometry. Optical reflection density is linearized through use of the function developed by Williams and Clapper [J. Opt. Soc. Am. 43, 595 (1953)] to convert reflection to transmission density. A wide variety of chemical assays are compatible with this format. As an example, for the glucose film we found coefficients of variation of 1.5% in predicting glucose concentrations in control sera during 20 days. Results for glucose concentrations in several hundred patients' sera by the present method were very cose to those obtained with the Center for Disease Control's hexokinase reference method.

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vol. 24 p 1335. In this paper, the equation, p 1340, relating Dt to Dr after integration should read See Equation in the PDF File In Table 3, the concentration units are mg/liter, not g/liter, and the day-to-day SD in glucose concentration at 999 mg/liter glucose is 15.1 mg/liter, not 1.51 mg/liter. In Table 4, p 1341, the concentration of Hypaque is expressed in mg iodine/L (mg I/L). p 1343. Table 3 was inadvertently omitted from this paper. It is as follows. See Table in the PDF File The table numbers for Tables 3–6 in the paper as printed should each be increased by one. p 1627. In Table 6, the numbers in the first line should read 580, 2260, 2210, and +50. The "+50" in the second line should be deleted.

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