Calibrating microarrays

1. An assay for simultaneously measuring an amount of a first analyte and developing a calibration curve in a sample, comprising the steps of:

(i) contacting the sample with a device that comprises:

one or more first reaction sites which comprise an immobilized first anlayte, or a first ligand having affinity for the first analyte, under conditions that permit binding between the first ligand and the first analyte, and a series of between 3 and 20 second reaction sites each comprising a second analyte, wherein different second reaction sites comprise the second analyte at different known concentrations;

(ii) removing any unbound first analyte;

(iii) contacting the device with a second ligand that is detectably labeled and which has affinity for the first analyte, and a third ligand that is detectably labeled and which has affinity for the second analyte under conditions that permit binding between the first analyte and the second ligand, and between the third ligand and the second analyte;

(iv) removing any unbound second and third ligands;

(v) measuring an amount of the second and the third ligands bound to a support; and

(vi) developing a calibration curve based on the measurement of the third ligand simultaneously with measuring the amount of the first analyte present in the sample.

2. An assay according to claim 1 , wherein the device is a support material comprising an array of discrete first reaction sites, each reaction site comprising the immobilised first analyte, or a ligand having affinity for the first analyte, and the series of second reaction sites comprising the second analyte, of different known concentrations, are immobilised on the support.