Abstract: A method and apparatus to estimate the concentration of a non-fluorescent substance (e.g. haemoglobin) in a fluorescent assay by separately estimating the non time dependent alteration attributed to inherent filter effects from the time dependent alteration caused by the assay chemistry. Such a method obviates the requirement for a separate photometric or other measurement thereby simplifying the methodology and associated instrumentation.

Abstract: A method and apparatus to estimate the concentration of a target substance (e.g. Cholesterol or CRP) in the plasma component of awhole blood sample without the need to separate the red blood cells from the plasma prior to testing, thereby simplfying the design and construction of the test device. The invention achieves this by measuring the analyte under investigation in a time dependent (bio-/immuno-) chemical reaction and measuring separately, a marker substance (e.g haemoglobin) for the estimation of red blood cell volume, using a non-time-dependent alteration in physical property of the reaction mixture (in this instance, transmission) attributed to inherent filter effects on sample addition. These non-time-dependent changes are not part of the reaction chemistry, and are resolved from the time dependent alteration in physical property caused by the assay chemistry by continuous measurement and mathematical modelling.