Charting Methods for Internal Quality Control of Indirect ELISA

This chapter deals with control charts to monitor the performance of Indirect ELISAs. An Indirect ELISA kit for the detection of antibodies against Brucella is used to demonstrate the methods. Many of the features explained in Chapter 9 are relevant to this chapter; some repetition is intended, as this chapter may be read independently. Figure 1 gives an overview of the indirect ELISA scheme used. The details of the procedure, which involves plotting the data graphically (charting methods), are explained. As a reminder, the objectives of charting data are as follows:

1.	To keep a constant record of all data.
2.	To monitor the assay from plate to plate in any one day's testing.
3.	To monitor the tests made from day to day, week to week, year to year.
4.	To allow rapid identification of unacceptable results.
5.	To allow recognition of reagent problems.
6.	To identify trends in results (increasingly poor performance).
7.	To identify when a new set of kit reagents is necessary.
8.	To allow identification of differences in operators of the assay.
9.	To fulfill various criteria for good laboratory practice.
10.	To fulfill necessary requirements for external recognition that tests are being performed at an acceptable level (increasingly important when results are used for international trading purposes).

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