Vault LIMS allows you to configure Lab Result Definitions 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 Lab Method, results from other Lab Methods, or a centralized list of calculation constants. Static Data Admins accomplish this by first adding Calculation Variables to the result definition, targeting them to other results or constants accordingly, then referencing them in the calculation formula.
Setting Up Calculated Results
To add a calculated Lab Result Definition:
- In a Lab Method create a new Lab Result Definition of type Numeric Result.
- In the Expected Data Entry Method field, select Calculation.
- Fill in the other fields as appropriate for the calculated result.
- Click Save.
To add variables to a calculated Lab Result Definition:
- In the Calculation Variables section of the Lab Result Definition record detail page, click Create.
- Select a type from the drop-down:
- Method Variable: The variable’s value is drawn from another result within the same Method.
- Cross-Method Variable: The variable’s value is drawn from a different Lab Method.
- Constant: The value of the variable is drawn from your Vault’s repository of established constants.
- Enter a Name. The Name value for a variable can only be made of letters and numbers, and cannot contain spaces.
- If you are creating a Method Variable, select a Target Result from the other results available in the current Lab Method.
- If you are creating a Cross-Method Variable, select a Result Type. The target result for this variable is determined while adding Lab Methods to Sample Definitions in a Lab Protocol.
- If you are creating a Constant, select a Target Constant.
- Click Save.
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
B2 by variable value
Note: Ensure that you leave a space after the variable name so Vault LIMS can distinguish a variable from other characters in the formula.
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:
- Navigate to a Lab Calculation Constants object tab.
- Click Create.
- Enter a Name.
- Select a Constant Type:
- Global: Allows a single Constant Value.
- Material: Allows you to define a Constant Value per Material.
- Click Save.
Once you have created your constant, add the appropriate constant value or 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:
- In the Constant Value section of a Lab Calculation Constant record detail page, click Create.
- Enter a Name.
- Enter a Value.
- If you are creating a value for a Material constant, select a Material record to associate it with.
- 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 Result Variable, it uses the latest Constant Value Version when passing the value into the result calculation. Because Lab 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 Lab Result Definitions, it also creates Lab Result Variables based on the variables attached to each Lab Result Definition. Those Lab Result Variables target specific Lab Results (in the same Lab Test or from another Lab Test) or Lab Calculation Constants that will contain the values needed for the calculation.
Because Lab Results are only created when a Lab Sample enters the Received state type, which creates the Lab Tests from Lab Methods, and Lab Results from Lab Result Definitions, it’s possible that a cross-test Lab Result Variable is created before the Lab Result it’s targeting has been created. In that situation, Vault LIMS creates the Lab Result Variable, and when the necessary Lab Result is eventually created, Vault LIMS will target the Lab Result Variable accordingly.
About Calculations in Test Execution
Calculated result values are generated when the Lab Test enters the In Review state type. When the Analyst clicks the Review button, Vault performs the following:
- Validates the calculation formula.
- Calculates the result.
- Evaluates the result against any existing specification criteria.
If Vault cannot resolve the calculation, or can’t put the value into the Lab Result, then the system captures the errors in the Lab Result’s Save Errors field.
If the calculated Lab Result is required, the Analyst cannot complete the Lab Test until a value has been populated into that Lab Result. If this occurs, check each of the Lab Result’s variables to see if there’s anything missing, or if the referenced Lab Results are not in the Testing Complete state type.
To view and manage calculation formulas, a user needs a permission set with View access to the Calculation Formula object control permission on the Lab Result Definition object.