Total test approach standardization

Taylor CR. The total test approach to standardization of immunohistochemistry. Arch. Pathol. Lab. Med. 2000 124 945-951. 

Several assumptions were made in using the broad MWD standard approach for calibration. With some justification a two parameter equation was used for calibration however the method did not correct or necessarily account for peak speading and viscosity effects. Also, a uniform chain structure was assumed whereas in reality the polymer may be a mixture of branched and linear chains. To accurately evaluate the MWD the polymer chain structure should be defined and hydrolysis effects must be totally eliminated. Work is currently underway in our laboratory to fractionate a low conversion polydlchlorophosphazene to obtain linear polymer standards. The standards will be used in polymer solution and structure studies and for SEC calibration. Finally, the universal calibration theory will be tested and then applied to estimate the extent of branching in other polydlchlorophosphazenes. 

These ideas have been employed to compute configurational entropy and hence test the AG relation via molecular simulation of several model systems.91-94,101,102 The approach used in those studies is conceptually simple. First, the total entropy of the fluid S is calculated by integration of standard thermodynamic relationships, for example, as discussed below. Then, the configurational contribution to the entropy Sc = S — Sv b, is approximated by subtracting from the total entropy an estimate for the vibrational contribution, Svib. 

It is desirable that the test substance concentrations in the samples lie within the linear part of the calibration curve, in order to keep the standard deviation of the measurement at an acceptable level. More concentrated sample solutions can be appropriately diluted, while a determinate amount of the test component can be added to less concentrated solutions to bring the total concentration up to the linear part of the calibration curve. However, the latter approach is of only limited importance because the presence of a constant amount of the test component may cause the relative changes in the sample concentration to become too small to measure precisely therefore, it is useful only when calibration curve slope varies rapidly with changing concentration [144). 

The second approach Intensifying radiation was tested in a phase III intergroup study (INT 0123/RTOG 94—05). This compared a modification of the best arm of RTOG 85-01 (standard therapy) to the same chemotherapy with a higher total dose of radiation. 

All these aspects have been recently studied in two publications (10.13). which standardized the dilution test for pungency and clearly established correlations with the estimates of total, and even individual, capsaicinoids. These papers also review the earlier attempts at standardisation. Two approaches are possible use of a fairly homogenous panel to determine the threshold pungency response due to the stimuli or use of a general panel to determine the average threshold of the panel for the stimuli. The second value will have wider applicability in use situations but the first value should be useful for correlative work. The two methods approach one another when panels are screened and trained to avoid all bias factors, and when carefully planned dilution levels, details of panel procedure, treatment of data, and expression of results are adopted. In fact, the results published in the two independent studies (10.13). show close values, 17+0.9 million for natural capsaicinoids and 16.1+0.6 million for pure capsaicin and dihydrocapsaicin. 

From the complexity of the above procedures, it is obvious that the result of the analysis depends on a large number of factors. The most general approach to the solution of the problem consists in elaboration of a standard procedure, its strict observation and its testing by means of an independent method, e.g., with the use of the sample compounds labelled with 14C. The determination of the total recovery by means of an internal standard, i.e., a chemically very closely related compound, a defined amount of which is added to the sample before the start of the procedure, is not exact as it is difficult to ensure that all of the properties of the standard that contribute to the final result are completely identical with the properties of the compounds being determined. With simpler procedures, when only a few different steps are applied, it is usually sufficient if a... 

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