Abstract: In one aspect, a kit for the semi-quantitative measurement, in a liquid sample, by competitive immunoassay, of a first member of a specific binding pair, the kit including a solid support bearinga reference area which provides a detectable signal in the immunoassay, anda first and a second test area exposed to contact the sample, each test area containing a different amount of second or first member of the specific binding pair,whereby the intensity of the detectable signal from the reference area can be compared with the intensity of any detectable signals from the first and second test areas in the presence of an unknown quantity of the first member in the sample.