Biochemical assay for AD7C-NTP in urine as an Alzheimer's disease marker

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Abstract
A reliable and specific immunoassay has been developed to detect and measure AD7C‐NTP, a biochemical marker for Alzheimer's disease, in urine. The urine samples are first processed by centrifugation and ultrafiltration to fractionate and concentrate AD7C‐NTP. The urinary AD7C‐NTP has the same molecular weight as AD7C‐NTP in brain and cerebro‐spinal fluid by size exclusion chromatography. It has also retained the binding properties to the monoclonal and polyclonal antibodies developed against recombinantly produced AD7C‐NTP. This assay is an enzyme linked sandwich immunoassay (ELSIA) using 96 well microtiter plates. The plate surface is coated with a monoclonal antibody (N3I4) which has a high affinity and specificity for AD7C‐NTP, capturing it effectively from the samples. The detection was achieved using a polyclonal antibody (ADRI). The utility of the assay has been demonstrated using urine specimens from Alzheimer's disease (AD) patients and non‐Alzheimer's controls. Urinary AD7C‐NTP in the AD group (2.5 ng/mL, n=66) was significantly higher than the non‐AD group (0.8 ng/mL, n=134).Using 1.5 ng/mL as cut off, in this patient population, specificity and sensitivity of urinary AD7C‐NTP were comparable to CSF AD7C‐NTP. J. Clin. Lab. Anal. 12:285–288, 1998.