Radioimmunoassay detection limits

A variation on the theme of conventional assay uses both lanthanide-labeled and biotin-labeled single strands to form split probes for sequence of target strands (Figure 12).120 When both of these bind to DNA, the complex binds (via the biotin residue) to a surface functionalized with streptavidin, immobilizing the europium and allowing assay to be carried out. This approach is already very sensitive to DNA sequence, since both sequences must match to permit immobilization of the lanthanide, but can be made even more sensitive by using PCR (the polymerase chain reaction) to enhance the concentration of DNA strands. In this way, initial concentrations corresponding to as few as four million molecules can be detected. This compares very favorably with radioimmunoassay detection limits. 

Gas Chromatography-Mass Spectrometry. In blood A -THC, initial screening by radioimmunoassay, detection limit 1 ng/ml—R. A. Bergman et al, J. analyt. Toxicol, 1981, 5, 85-89. 

Gas Chromatography-Mass Spectrometry. In plasma comparison with radioimmunoassay, detection limits 110 pg/ml and 20 pg/ml respectively—J. E. Peterson era/., J.pharm. Sci., 1979, 68, 1447-1450. 

Pedersen etal., (2003) [Denmark] Moderate and mild ID Tg-Ab Radioimmunoassay TPO-Ab Radioimmunoassay Detection limits 18-65 Tg-Ab 13.0 TPO-Ab 13.1... 

Hollowell etal., (1998) [United States] Iodine suffioient Tg-Ab Radioimmunoassay TPO-Ab Radioimmunoassay Detection limits 12-1- Tg-Ab 11.5 TPO-Ab 13.0... 

Methods of detection, metabolism, and pathophysiology of the brevetoxins, PbTx-2 and PbTx-3, are summarized. Infrared spectroscopy and innovative chromatographic techniques were examined as methods for detection and structural analysis. Toxicokinetic and metabolic studies for in vivo and in vitro systems demonstrated hepatic metabolism and biliary excretion. An in vivo model of brevetoxin intoxication was developed in conscious tethered rats. Intravenous administration of toxin resulted in a precipitous decrease in body temperature and respiratory rate, as well as signs suggesting central nervous system involvement. A polyclonal antiserum against the brevetoxin polyether backbone was prepared a radioimmunoassay was developed with a sub-nanogram detection limit. This antiserum, when administered prophylactically, protected rats against the toxic effects of brevetoxin. 

Standard curves performed under our defined radioimmunoassay conditions ([ H]PbTx-3 = 1 nM, antiserum dilution = 1 2000, assay volume = 1 ml) demonstrated the ability of this antiserum to bind equally to PbTx-2 and PbTx-3, suggesting specificity for the cyclic polyether backbone region of the molecule (Figure 8). The linear portion of the curve indicated a lower detection limit of 0.2-0.5 ng in saline buffer under these conditions. Evaluation of this assay for use with biological fluids and tissue extracts is underway. 

Figure 8. Standard curves for PbTx-2 ( ) and PbTx-3 ( ) in the brevetoxin radioimmunoassay. Lower detection limits are 0.2 — 0.5 ng in phosphate-buffered saline (PBS). Standard RIA conditions [ H]PbTx-3 = 1 nM antiserum dilution = 1 2000 sample vol. = 1 ml buffer = 0.1 M PBS, pH = 7.4.

Radioimmunoassay. In plasma detection limit 10 pg—B. Gourmeletfl/., Clinicachim. Acta, 1980,108,229-237. In plasma diacetalol—B. Gourmcletal., Clinicachim. Acta, 1981,115, 229-234. 

Quantification. Radioimmunoassay. In plasma or serum atropine and hyoscyamine, detection limit 2.5 ng/ml for both compounds—R. Virtanen et al., Acta pharmac. tox., 1980, 47, 208-212. 

High Pressure Liquid Chromatography-Radioimmunoassay. In plasma fluphenazine, related phenothiazines and metabolites, detection limit 160 pg for fluphenazine—S. A. Goldstein and H. Van Vunakis, J. Pharmac. exp. Ther., 1981, 217, 36- 3. 

Radioimmunoassay. In plasma detection limit 1 ng/ml—I. M. McIntyre et ai, ibid. 

Radioimmunoassay. In serum thyroxine and liothyronine, detection limit 10 ng/ml and 260pg/ml, respectively—C. E. Denning et al., Clinica chim. Acta, 1979, 98, 5-18. 

Enzymes are currently the most widely used and investigated labels for immunoassays, because a single enzyme label can provide multiple copies of detectable species. This catalytic amplification results in immunoassay detection limits that rival those of radioimmunoassay without the storage and disposal problems associated with radioisotopes. Enzyme immunoassays label either ligands or antibodies with enzyme, and enzyme activity in bound or free fractions is measured. Heterogeneous immunoassays employing enzymatic labels have been named enzyme-linked immunosorbent assays (ELISAs). ELISA methods usually employ antibody immobilized onto the wells of polystyrene microtiter plates, and may be... 

Radioimmunoassays can detect ricin in blood at concentrations as low as 50-100 pg/mL (Godal et al., 1981). Colorimetric ELISA methods can detect ricin spiked into ex vivo human serum or urine samples accurately at levels as low as 1 ng/mL (100 pg/well) with acceptable inter- and intraassay variation (Poli et al., 1994). Chemical luminescence-based ELISA technology improves the detection limit to 0.1-1 ng/mL ricin, but the coefficients of variation may be as high as 50% (Poli et al., 1994). Combination of a sensitive immunological assay with PCR amplification may achieve a limit of detection for ricin at levels as low as 10 fg/mL (Lubelli et al., 2006). 

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