Slope ratio assays

The activity of hyaluronidase is determined by comparing the rate at which it hydrolyzes sodium hvahironate BRP with the rate obtained with the International Standard or a reference preparation calibrated in I.U. using a slope-ratio assay. 

DRelative Biological Value determined by slope-ratio assay. cRelative Biological Value is calculated (Pla and Fritz,... 

Susenbeth, A., A. Agunbiade and J. Dohms, 2001 Bioavailability of lysine of several protein sources determined by the slope-ratio assay in pigs. In Fevrier, C., Aumaitre, A., Habe, E, Vares, T, Zjalic, M. (eds.). Protein Feed for Animal ProductiotL EAAP Technical Series 2001 133-137. 

Saponin analysis of these products and of the alfalfa sprouts was by the procedure of Livingston et al. (1977). The samples were assayed in duplicate at three levels using a Trichodernia bioassay, comparing the results with a standard saponin, calculating saponin by means of a slope ratio analysis. 

It has been suggested by Wood (53) that, for those microbiological assays which show a strictly linear portion to the standard curve, the so-called slope-ratio method diould be used for calculating the results. This method, of course, has the merit of being statistically sound, and it also has the valuable advantage that it is possible to calculate the fiducial limits of an assay. 

Unfortunately, the slope-ratio method of calculation has only a very restricted use in the computation of microbiological assay values. It is the exception rather than the rule that the mean response to a tube assay is linearly related to the dose, i. e., that there is a strictly linear portion of the standard curve. In the vast majority of assays, there is no linear portion of the standard curve which is curvilinear throughout its length. 

Calculated as the ratio of the calibration sensitivities (or slope m) of the different cellodextrin standard curves to the glucose standard curve. Thus, a ratio of 1 is expected, theoretically, for a true reducing sugar assay, which has the same molar color yield for a series of saccharides. 

F0BMUIM.S Required in Obtaining Slope Indices and Potency Ratios for Assays in Which All Plasuas Are Tested... 

All treatment times were 1 h. DPC was quantified immediately after treatment ISC, 6 h later. The ratios of the slopes of these lines (K25/ZCR9) are 3.0 for DPC and 2.5 for ISC. The ratio for relative colony formation (survival) was 2.4 (ZCR9/K25). These ratios represent the ratios of cis-DDP doses producing equal effects in each assay. 

An inoculum reference graph has been prepared which relates the density of the inoculum to the volume required to yield zones of the best character and a dose-response slope that shows the greatest difference in response for standard dose increments. This corresponds to an assay medium containing 10 cells per milliliter. It is assumed that the variation from day to day in the ratio of viable to total bacterial cotmt is insignificant. 

In most biological assays a linear relationship is established between the response or a function of it (— y) and the logarithm of the dose administered = x). Lines are fitted for standard and test by the method of least squares, and if these lines are parallel within the limits of experimental error, a mean slope is calculated. The log activity ratio is equal to ... 

There still remains a small group of biological assays in which the response or a function of it is linear to the dose itself, a relationship which is satisfied by the data to be obtained from chemical or physio-chemical methods of assay. The relative activity of the two preparations is, in these assays, the ratio of the slopes of the two regression lines providing the lines converge, within the limits of experimental error, at zero dosage. 

The simplest design is that in which the preparations are examined at one level and a blank is also carried out. If the blank gives zero response the ratio of the slopes is the ratio of the two readings themselves or, if the blank has a value, the ratio of the two readings each diminished by the blank value, an operation which is regularly applied in chemical assays. 

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