Assay turnaround time

Another antibody-based method is immunoligand assay (ILA) technology. The Threshold system (Molecular Devices, Sunnyvale, CA) shortens assay development and assay turnaround time.11 It adapts a sensitive detection system originally... 

Assay methods used for TDM should be accurate and reproducible. All clinical laboratories with a TDM service should be actively involved in an internal quality control and external proficiency testing program. In addition, sample volume and assay turnaround time should be considered in selecting the most appropriate analytical method,... 

Selecting an antibody 297 Selecting an assay standard 297 Sample matrix 299 Sample preparation and dilution 299 Assay turnaround time 300... 

In current practice the fluorescence assay is often followed by the use of hybridization techniques when more selectivity is required. We have for instance used the fluorescence techniques to obtain data on the nucleic acid content of malaria vaccine proteins produced in Escherichia coli. The rapid turnaround time of the fluorescence assay is particularly useful during the early stages of purification to determine the optimal process conditions. After the final process has been arrived at and a variety of methods used to assess the nucleic acid content (including the hybridization techniques), the fluorescence method can be developed for routine quality-control purposes. In certain cases, particularly at high protein concentrations, the dye may bind to the protein with... 

For high quality data, assays that are homogeneous and robust are selected. Also, whenever possible, preference is given to assays based on human sources. Finally, miniaturized assays are preferred for their fast turnaround time and low cost. 

The need for shortening the time and increasing the sensitivity for detection of antigens has lead to development of different amplification systems. Some of the initial efforts focused on use of more pure antibodies (59, 60), more specific monoclonal over less specific polyclonal antibodies (61) and use of a combination of monoclonal antibodies (62). The next phase saw the incorporation of labels as discussed in the previous section. The use of labels does increase the sensitivity however, there is a need to go down in detection levels to enable faster turnaround time for immunoassays. This can mean significant savings in the food industry. In the case of Salmonella, the assay time is being reduced from several days to less than a day (63, 64). 

The pressure of a fast turnaround time for the expensive LC-MS instrument and false confidence in MS mass resolution power often leads to compromised methods with shortened chromatographic runs. With limited sample clean-up for macromolecules and inadequate chromatographic separation, matrix components can co-elute with the analyte. They may compete for the limited charge or impede (or promote) movement of the analyte ions to the surface of the droplets, resulting in matrix effects [54]. Matrix effects can impact on selectivity, sensitivity, linearity and reproducibility of the assay. For ESI, competition for ionization can occur both in the mobile phase and the gas phase [55]. The pH, volatility, and surface tension of the mobile phase will affect ionization efficiency. The major suppres-... 

The selection of appropriate methods for clinical laboratory assays is a vital part of rendering optimal patient care, and advances in patient care are frequently based upon the use of new or improved laboratory tests. Ascertainment of what is necessary clinically from a laboratory test is the first step in selecting a candidate method (Figure 14-1). Key parameters such as desired turnaround time and necessary clinical utflity for an assay can often be derived by discussions between laboratorians and clinicians. When introducing new... 

Important assay characteristics for immunochemical methods include (1) limit of detection, (2) precision, and (3) turnaround time. 

Radioimmunoassay (RIA) techniques permit quantification of drug concentration in microliter volumes of. serum at nanograms per milliliter concentrations. However, the complexity of this technique, long turnaround time, problems, with waste disposal, and lack of RIA for a wide variety of drugs have prevented its widespread adoption for routine drug assays. Few RIAs now are used for TDM. 

Once it is determined which ligand binds to a specific target (and with what relative affinity), the results are tabulated and written to a proprietary corporate database. The rapid turnaround time provides chemists and molecular modelers with immediate feedback as to the affinity of compound collections to the target(s) of interest. Thus, the MASS assay is an invaluable tool in the structure-activity-relationship optimization cycle and represents an exciting new paradigm for lead identification in the drug-discovery arena. 

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