Patent ID: 7943331

Claim:
A method of carrying out an assay for substance in a sample of whole blood, which method comprises: (a) carrying out a reaction in solution between an analyte in the whole blood sample and a specific reagent, the sample being combined with the reagent at time t 0 ; (b) monitoring the transmission of the solution continuously as the reaction progresses at a suitable wavelength; (c) recording, from the detected transmission values, the transmission, T init , being the transmission of the reaction solution before the addition of the sample; and calculating T 0 , being the transmission at time t 0 after the sample has been added and T ∞ being the transmission at time t ∞ , which is the point at which all of the analyte has reacted with the reagent, or has attained equilibrium; (d) calculating from the values of T init and T 0 the optical density of the sample after blood addition and hence quantity of haemoglobin added in that sample; (e) calculating from the values of T 0 and T ∞ the change in transmission attributable to the reaction in step (a); and (f) deriving from the relationship between these measurements the concentration of the analyte in the sample, corrected for haematocrit variation.