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Summary: This paper describes a fully automated assay on the Serono SRI™ for the measurement of cortisol in serum, heparinised plasma and urine. The assay incorporates a specific polyclonal antibody to cortisol and cortisol conjugated to alkaline phosphatase as a label. Following immunoincubation, bound and free labelled cortisol are separated by magnetic sedimentation of the antibody complex. Phenolphthalein is liberated by the enzymatic hydrolysis of the substrate (phenolphthalein monophosphate) and the absorbance generated is measured as the assay end-point. All processing steps are performed by the SRI.The assay has good analytical performance with respect to precision (within and between run CVs less than 10 and 11.5% respectively), detection limit (less than 5 nmol/1) and recovery of added cortisol (100 ± 10%). The assay agrees well with cortisol concentrations determined by ID-MS and by established immunoassays (r > 0.96). Reference ranges of normal urine samples (pretreated by solvent extraction) are in good agreement with accepted values.The study demonstrates that the SRI Cortisol assay on the SRI analyzer is suitable for the routine determination of cortisol in serum, heparinised plasma and urine samples. Introduction^, . x , , ·ι_.ι_ r r* r 11

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The Fluorescence Capillary Fill Device (FCFD) has previously been shown to be a candidate test vehicle for the point of care market and instrumentation suitable for commercialisation has now been developed. The FCFD instrumentation is a fluorimeter with custom optics to collect a given angular spread of light from the output edge of the device. Rigorous selection of fluorophore, light source, filters and detector (taking into account cost, availability in manufacturing quantity and the influence of inherent blood fluorescence) was undertaken when optimising the system. The instrument utilises allophycocyanin as a near-red fluorophore, an array of ultra-bright light emitting diodes and an inexpensive photomultiplier. Assay calibration is achieved by incorporating a light source movement mechanism that allows reference zones within the device to be interrogated individually. The resulting instrument has a footprint approximately 10 inches by 8 inches, requires no specialist operator training and is well suited to the point of care market. The capability of the system is illustrated by a whole blood assay for the cancer marker prostate specific antigen (PSA). This assay has a sensitivity of