xChek*: Creating a User-Defined Assay for the PRVgB Antibody ELISA
(Short Protocol)

Creating a user-defined assay is an easy process of two tasks—editing an xChek file to allow you to create an assay, and then creating the assay within xChek.

To edit the xChek.ini file:

1. From the task bar, choose Start> Run and type "xchek.ini" into the text box. Click the OK button.
2. After the xChek.ini file opens, locate the line labeled "AllowNewAssays".
3. If the value for that line is "0", change it to "1". If the value is already "1", do not do anything.
4. Locate the section labeled [Basic Graphs], scroll to the end of the section and then enter "PRVgB=12".
5. From the menu bar, choose File> Save, and then choose File> Exit.

To create the assay:

1. From the task bar, choose Start> Programs> xChek> xChek to open the xChek program.
2. From the menu bar, choose Database> Assays> All to open the Assay dialog box.
3. Click the New button and enter "Pseudorabies Virus gB short protocol" into the Name field, "PRVgB" into the Code field, and "Unknown" into the Kit Lot field. Today's date (mm/dd/yyyy) is automatically entered into the Expiration field.


NOTE: When you begin testing, update the information in the Kit Lot and Expiration fields with the actual kit lot number and expiration date.



4. Click the Basic button and select or enter the following information for the respective fields:

   Case Type: Animial	Samp Filter: 650
   Template: SIV Horizontal	Ref. Filter: 0
   Species: Cattle	Dilution: 2
   Technology: ELISA	Wells: 1

   
   NOTE: Due to a problem with selecting swine as the species type in versions 3.2 and 3.3 of xChek, the species used for this user-defined assay is cattle.

   

5. Click OK to save the settings.
6. Click the Calculations button and select or enter the following information:
   Formulas:
   • "S" Part of Ratio: Sample1
   • "P" Part of Ratio: None
   • "N" Part of Ratio: Negative
   
   First Calculation:
   • Variable: S/N
   • Positive Cutoff: 0.6
   • Suspect Cutoff: 0.7
   • Comparison: <=



7. Click OK to save these settings, and then click the OK button to save the assay to the database. You can now test for PRVgB (short protocol) using the xChek Assay Management System.

NOTE: xChek does not evaluate controls or results for validity when you use a user-defined assay. You must evaluate the results from each assay in accordance with good laboratory practices. To evaluate your assay validity, please refer to the "Results" section in the insert provided with the test kit.

Setting Up Additional Display Variables
Only OD values are displayed in the reporting options for this user-defined assay. To set up additional display variables, follow the directions below.

1. From the xChek menu bar, choose Reports> Analyze Cases to open the Filter Criteria for Analyze dialog box.
2. Enter the desired search criteria and click OK. The Select Cases for Analyze dialog box appears.
3. Select the desired cases and click OK. The Analyze Report dialog box appears.



4. Click the Variables button to open the Display Variables dialog box.



5. Select the desired options and click OK. Click OK again to save the settings.

For more information, call IDEXX Technical Services at 1-800-548-9997 (in the U.S.) or 1-207-556-0890 (outside of the U.S.).