Methods for determining the concentration of an analyte in the plasma fraction of a sample of whole blood

A lateral flow assay method for handling a sample of whole blood and determining a level of an analyte in a plasma fraction of said sample, comprising a step of determining a hematocrit value of said sample and applying said hematocrit value when determining the level of said analyte in said plasma fraction, characterized in that the method comprises the steps

• i) diluting said sample with a substantially non-hemolysing buffer to a pre-determined dilution factor, producing a diluted sample,
• ii) applying said diluted sample to a substrate of a lateral flow assay device,
• iii) taking an image of said substrate at a predetermined wavelength within 1-600 seconds from when the applied sample has been absorbed in said substrate, wherein the predetermined wavelength is based on the dilution factor used in step i),
• iv) analysing said image to determine a reflectance value from said image,
• v) correlating said value to values obtained for samples having known hematocrit values to obtain a value of hematocrit for said sample,
• vi) determining the level of said analyte down-stream in said lateral flow assay device, applying the dilution factor used in (i) and the hematocrit value of the sample obtained in (v) when determining the level of said analyte in the plasma.