LIMS Calculations

Vault LIMS allows you to configure Test Definition Results as calculated results, populating the result value at runtime according to a formula you define in the result definition.

These calculation formulas can reference other results in the same Test Definition, results from other Test Definitions, or a centralized list of calculation constants. Design Data Admins accomplish this by first adding Calculation Variables to the result definition, targeting them to other results or constants accordingly, and then referencing them in the calculation formula.

For example, suppose that a pH test is run in triplicate:

ph Result1: 6.5

ph Result2: 6.0

ph Result3: 6.2

ph Average (rounded to 1 decimal place): 6.2

The calculation formula might be Average($BVR1, $BVR2, $BVR3) where BV stands for a Basic Variable that was created for each pH Result.

Setting Up Calculated Results

To add a calculated Test Definition Result:

  1. In a Test Definition object record create a new Test Definition Result of type Numeric Result.
  2. In the Expected Data Entry Method field, select Calculation.
  3. Fill in the other fields as appropriate for the calculated result.
  4. Click Save.

To add variables to a calculated Test Definition Result:

  1. In the Variables section of the Test Definition Result record detail page, click Create.
  2. Select a type from the drop-down:
    • Basic Variable: The variable’s value is drawn from another result within the same Test Definition.
    • Cross-Test Variable: The variable’s value is drawn from a different Test Definition.
    • Constant Variable: The variable’s value is drawn from your Vault’s repository of established constants.
    • Aggregate Variable: Multiple results may be located and passed into the calculation.
  3. Enter a Name. The Name value for a variable can only be made of letters and numbers, and cannot contain spaces.
  4. If you are creating a Basic Variable, select a Target Test Definition and then a Target Test Definition Result.
  5. If you are creating a Cross-Test Variable or an Aggregate Variable, select a Target Test Definition, Target Test Definition Result, and Scope.
  6. If you are creating a Constant Variable, select a Target Constant.
  7. Click Save.

The target result of a variable is identified using the Trace ID of the Test Definition and Test Definition Result. Once you have created your variables, you can define the formula for the calculation.

Defining a LIMS Calculation Formula

LIMS calculation formulas follow standard Vault formula construction with the following additions:

  • Variable names are always preceded by a dollar sign ($). Typing $ will cause the formula builder to display all available variables for quick insertion.
  • You can click the Variables tab to see all available variables.

For example, the formula ( $A1 - $B2 ) / $C3 will divide the difference of the variable values A1 and B2 by variable value C3.

Note: Ensure that you leave a space after the variable name so Vault LIMS can distinguish a variable from other characters in the formula.

Calculation Constants

Vault LIMS allows you to manage a central library of constants for use in Calculation Variables. Calculation Constant records contain one or more Constant Value records, allowing calculation formulas to refer to the Calculation Constant and for Vault LIMS to automatically select the appropriate Constant Value according to the type of Constant (Global or Material) and Material on the Batch.

To create a Lab Calculation Constant:

  1. Navigate to a Lab Calculation Constants object tab.
  2. Click Create.
  3. Enter a Name.
  4. Select a Constant Type:
    • Global: Allows a single Constant Value.
    • Material: Allows you to define a Constant Value per Material.
  5. Click Save.

Once you have created your constant, add the appropriate constant value or values.

Constant Values

Each Lab Calculation Constant must contain at least one (1) Constant Value in order to be used in a Calculation Variable. To create a Constant Value:

  1. In the Constant Value section of a Lab Calculation Constant record detail page, click Create.
  2. Enter a Name.
  3. Enter a Value.
  4. If you are creating a value for a Material constant, select a Material record to associate it with.
  5. Click Save.

Global constants only contain a single Constant Value. Material constants can contain multiple values, but each must be associated with a specific Material record.

About Constant Value Versions

To ensure traceability, Vault LIMS automatically creates Constant Value Version records every time you edit a Constant Value record. When Vault LIMS selects a constant for a Lab Test Result Variable, it uses the latest Constant Value Version when passing the value into the result calculation. Because Lab Test Result Variables at Lab Test creation target specific Lab Calculation Constant Value Version records, you can freely update the Value field on the Constant Value record without affecting currently running Lab Tests.

About Variable Dependency in Calculated Lab Results

When Vault LIMS creates Lab Results from Test Definition Results, it also creates Lab Test Result Variables based on the variables attached to each Test Definition Result. Those Lab Test Result Variables target specific Lab Results (in the same Lab Test or from another Lab Test) or Lab Calculation Constants that contain the values needed for the calculation.

Because Lab Results are created when the Generate Tests action is run, which may be at any time, it’s possible that a cross-test Lab Test Result Variable is created before the Lab Result it’s targeting has been created. In that situation, Vault LIMS creates the Lab Test Result Variable, and when the necessary Lab Result is eventually created, Vault LIMS will target the Lab Test Result Variable accordingly.

About Calculations in Test Execution

Calculated result values are generated when a Lab Test is completed. When generating calculated result values, Vault performs the following:

  1. Validates the calculation formula.
  2. Calculates the result.
  3. Evaluates the result against any existing specification criteria.

If Vault cannot resolve the calculation, or enter the value into the Lab Result, the system captures the errors in the Lab Result’s Save Errors field.

If a Lab Test is marked as invalid, none of its Lab Results are included in calculations.

Related Permissions

To view and manage calculation formulas, a user needs a permission set with View access to the Calculation Formula object control permission on the Test Definition Result object and Create, Edit, and Delete permissions on the Test Definition Result object.