Disclosed is an improvement to a dry assay device for determining the
concentration of a first analyte in a sample of body fluid and a second
analyte in the same sample of body fluid. The device involves the use of a
strip of an absorbent material through which the sample of body fluid
flows and wherein the first analyte is determined colorimetrically in a
first region of the strip and the second analyte is determined by an
immunoassay which takes place in a second region of the strip located
downstream from the first region. The improvement involves placing the
strip in a hollow casing having a top and a bottom and which is so
constructed that when the top and bottom of the casing are mated there is
formed a U shaped, body fluid impervious barrier around the first region
of the strip to prevent the sample of body fluid from flowing in any
direction other than in the direction of the second region of the strip.
