Gold standard curve

This maximizes Se (Se l). However, specificity will be minimized as most of the inactive molecules will be in the selection. The situation is reversed in the case where n is very small (n 0). Consequently, one cannot optimize both Se and Sp at the same time and a trade-off is to be determined. If one can choose to rely on one of the above metrics to find an optimum, we have recently advocated the use of a simpler graphical technique which has been adopted as a gold standard in many other research areas the receiver operating characteristic (ROC) curve method [53]. 

Acceptance criteria for an insulin assay are less than 15% interassay CV. Minimum detectable concentration of insulin, as calculated from the calibration curve, should be 1 pIU/mL with the overnight procedure or 3 pIU/mL with the same-day procedure. In addition, recovery and linearity should be 100 15%, and the in-house insulin calibrator should be within 5% of the gold standard. No gold standard was specified. 

At a minimum, documentation of the characterization and stability of a standard, such as a certificate of analysis (Co A) and/or a certificate of stability (CoS), is typically available from the suppliers. The certificate should be obtained and recorded. The quantity of reference standard is typically limited in commercial kits designed for research use, and it is not uncommon that the reference material values may differ substantially between lots and manufacturers [16]. Novel biomarkers rarely have established gold standards against which their potency and abundance can be calibrated. A comparison of available sources can be useful, and when validating an assay for advanced applications it is desirable to plan ahead to obtain and reserve a sufficient supply of the same reference material. The example in Fig. 6.5 compares three reference standard curves, each prepared from a concentrated stock solution from a commercial supplier, an in-house reference standard, and a commercial kit, respectively. The instrument responses (optical density, OD) were highest with the standard from the commercial stock, the lowest with the kit, while the in-house reference standard response was intermediate. In this case, either the same commercial stock or the in-house reference standard can be used throughout the clinical study. 

Consequently, mirror optics are more common, in particular in the mid-IR. The mirrors used are usually aluminium- or gold-coated flat or curved substrates. While near-IR mirrors are usually protected by thin SiO-layers, in the mid-IR unprotected mirrors have to be used. Disadvantages of mirror optics are the elevated space consumption and the higher prices in comparison to refractive optics, especially comparing non-standard mirrors against non-standard lens. In total, mirror optics are so preferable to fibres and refractive optics, at least in the mid-IR, that in some technical applications they are used to replace waveguides to transport IR radiation between source, sensor head and spectrometer. 

Chronoamperometric curves have been used as a standard tool to obtain values of the rate constants of surface-bound molecules and they prove as very useful for validating the Marcus-Hush s formalist, and, indeed, the experimental application of the MH theory to electrode processes has been mainly carried out with surface-bound redox systems. Thus, Chidsey studied the oxidation of ferrocene groups connected to a gold electrode by means of a long alkylthiol chain by using Single Potential Pulse Chronoamperometry (see examples of the experimental responses in Fig. 6.21) [43]. 

Repeat die procedure widi 1 ml of each of the diluted standard solutions, and with 1 ml of sodium chloride-potassium chloride solution (blank). Plot the absorbance of each standard solution against the concentration of gold, and read off die concenhation in the sample. The calibration curve should be linear in the range 0.5 to 2.5 jag/ml. 

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