Dose-response curve, immunoassay

Figure 14.14. Competitive Uuorescence lifetime immunoassay dose-response curve ( ), in which the analyte, human IgG, competes with eosin-human IgG for fluorescein-anti-human IgG binding sites. Fluorescence lifetime changes of fluorescein-human IgG donor in the presence of increasing amounts of eosin-human IgG acceptor are also shown (o). (From Ref. 107 with permission.)...

Figure 14.16. Dose-response curves for a phase fluorescence immunoassay of thyroxine at modulation frequencies of 49.5 MHz ( ), 64.8 MHz (a), and 99.1 MHz (o). (From Ref. 34 with permission.)...

Figure 6.22 PWG assay dose precision profiles of multiplexed three-analyte immunoassay for two sets of experiments. Dose precisions correspond to standard deviations of analyte concentrations that were back-calculated using corresponding dose response curves. (From Pawlak, M. et al., Proteomics, 2, 383-393, 2002. With permission.)...

Fig. 2. Typical dose-response curves of (A) competitive immunoassays and (B) noncompetitive immunoassays.

Dose-response curves of (O) noncompetitive and ( ) competitive immunoassays of UDCA... 

The 4-parameter logistic model is considered the most versatile one for fitting the dose-response curves in immunoassays [42]. The fitting equation is given by [22, 23, 41]... 

With constant random error, the precision of an RIA increases as the slope of the dose-response curve increases and decreases as the error increases with constant slope. Future availability of monoclonal antibodies may greatly increase the steepness and improve the shape of the resulting dose-response curve. As with any analytical techniques, it is crucial to appreciate the confidence intervals which one has at various points of the dose-response curve, in addition to the many measurement and collection errors which may be made before the immunoassay is employed. 

Figure 10.3 Typical dose-response curve for an immunoassay.

Fig. 14,1. Basic competitive and non-competitive immunoassay designs. (A) Non-competitive immunoassays use paired antibodies directed against different parts of the analyte molecule. The first antibody is used to capture the analyte from the sample and the second, labelled antibody to measure the amount of analyte bound, resulting in a response directly related to the concentration of analyte in the sample. (B) Competitive immunoassays use labelled antigen to measure unoccupied sites, resulting in a sigmoidal dose-response curve where the signal is inversely related to the concentration of analyte in the sample.

For most immunoassays, the mean response is a non-linear function of the anal3de concentration (the dose-response curve) and the variance of replicate measurements is a non-constant function of the mean response, as seen in Fig. 9.3. 

High sensitivity is an intrinsically desirable property of any anal3d ical technique. The definition of sensitivity has, however, become a subject of considerable controversy particularly for immunoassays, being considered by different scientific groups as the slope in the middle of the dose-response curve [8,9], the midpoint ofthe dose-response curve (IC50) [10] or the minimal... 

In contrast to competitive immunoassays, the number of theoretical models describing the kinetics and thermodynamics of non-competitive immunoassays is considerably lower and most of them are derived from double-site immunometric configurations. The dose-response curve for such assays is sigmoid the signal increasing with the analyte concentration with a plateau value reached when the capture antibody becomes saturated. 

Figure 9-13 A schematic diagram of the dose-response curve for a typical immunoassay.The analytically useful portion of the curve is bracketed by points a and b.

Figure 11 F-3 Dose-response curve for determining drugs by fluorescence-based immunoassay.

Fig. 3. Left dose-response curves for HRP. Right calibration curves obtained from a sandwich chemiluminescent enzyme immunoassay for Yersinia, enterocolitica.

Cyclic voltammograms of working electrodes in the presence of antibodies other than anli-bioiin IgG produced no anodic peaks. For analyte solutions contain ing anti-biotin IgG, CV peak currents were proportional to the concentration of the analyie. and working dose-response curves of CV peak current versus concentration provided an effective means for completing the immunoassay. The detection limii is O.l pg/ml.. and the range of the technique is 0.1 to 1(K) pg/mL of anii-bioiin IgG. 

Fig. 5.15 Two approaches to increase a speed and specificity of immunoassays, a Scheme of rotating assay, b Dose-response curves for the SERS-based detection of rabbit IgG in PBS with and without rotation. The dashed lines represent the iowest detectabie signal Iot assay, c Scheme of three-step assay using Au-piated membrane as the capture substrate and a syringe for active transport (adapted with ptamission from Driskeil et ai. 2007 (a, b) and Penn et al. 2013 (c). Copyright 2007, 2013 American Chemical Society)...

Figure 2 Typical enzyme immunoassay calibration curve illustrating the inversely proportional dose-response relationship...

Y is the expected response and X is the corresponding concentration. A, B,C and D are the four parameters of the equation, where A gives an estimate of expected response at zero dose, B is the slope (e.g., response/concentration) in the middle of the calibration curve, C is the IC50 and D is the expected response at infinite dose. This curve satisfies all the conditions specified for the response-concentration relationship and also closely approximates the mass-action equations [20]. Weighting of the results is recommended for fitting dose-response data from immunoassay, in order to compensate the heterogeneity of response variances in the response-error relationship [17,18]. 

Figure 9 Standard calibration curve for sandwich enzyme immunoassay for rabbit IgG using the ALP-phenyl phosphate E-S pair. The bracketed point is the zero dose response.

Capillaries modified as above have been used in several heterogeneous enzyme immunoassays, both competitive and sandwich. The calibration curve for a rabbit IgG assay in human semm controls is shown in Figure 12. The zero dose-response was 7.5 nA using the ion-pairing agent pentane sulfonate. The final... 

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