Ultrasensitive assays

Ultrasensitive assays for PSA contribute to the earlier detection of prostate cancer relapse and (or) residual disease in prostatectomized patients as well as the more timely evaluation of response to current therapies. PSA determinations can be useful in detecting metastatic or persistent disease in patients following surgical or medical treatment of prostate cancer. Persistent elevation of PSA following treatment, or an increase in the pretreatment PSA concentrations, is indicative of recurrent or residual disease. Hence, PSA is widely accepted as an aid in the management of prostate cancer patients, and serum levels are most useful when sequential values are obtained and monitored over time. After complete removal of the prostate gland (radical prostatectomy), PSA levels should become very low or undetectable. A rise of the serum PSA level in prostatectomy patients indicates residual prostate tissue, recurrence, or metastasis of the disease (13, 16, 24, 36). 

Soleas GJ, Yan J, Goldberg DM. 2001b. Ultrasensitive assay for three polyphenols (catechin, quercetin and resveratrol) and their conjugates in biological fluids utilizing gas chromatography with mass selective detection. J Chromatogr B Biomed Sci Appl 757 161-172. 

Tg, 50H5,6H2T, 5,6H2T, 5HmU and 50H5MeHyd are readily detected by GC/ MS after excision from the damaged DNA and trimethylsilylation (Chap. 13.2). For the Tg lesion, an ultrasensitive assay is also available that even allows its detection in cells at a dose as low as 0.25 Gy and to follow its repair (Le et al. 1998). 

Stenman UH. New ultrasensitive assays facilitate studies on the role of human glandular kallikrein (hK2) as a marker for prostatic disease [editorial comment], Clin Chem 1999 45 753-754. 

Although the core steps of IPCR, DNA-antibody coupling, and DNA detection were discussed in detail earlier, the actual performance of the ultrasensitive assay requires some more considerations from the clinical laboratory scientist. A number of different protocol details and experience in IPCR assay fine-tuning were collected during the experimental work of several researchers. In the following paragraphs, the basic requirements of an optimized IPCR protocol are discussed ... 

Figure 9-14 Ultrasensitive assays for horseradish peroxidase and alkaline phosphatase labels. A, Chemiluminescent assay for horseradish peroxidase label using luminol. B, Chemiluminescent assay for an alkaline phosphatase label using AMPPD.

Both traditional and ultrasensitive assays are available for measuring PSA. 

The lowered detection limits of the newer two-site immunoassays for the measurement of pituitary hormones now make it possible to distinguish an abnormally low value from the lower end of the normal reference interval. Although assessment of a particular aspect of pituitary function should also include clinical signs and symptoms of hormone deficiency and the measurement of hormones secreted by the pertinent endocrine gland (e.g., T4, cortisol, and testosterone), the newer, ultrasensitive assays for TSH, FSH, LH, and ACTH allow for an accurate distinction of a true low result from low normal. A scheme for testing of pituitary reserve is fisted in Box 50-6. 

Le XC, Xing JZ et al (1998) Inducible repair of thymine glycol detected by an ultrasensitive assay For DNA damage. Science 280 1066-1069... 

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