7 Calculations

   Table of Contents...

Calculations

Powerful. Calculations are used to determine Analysis results by applying a formula to dependent results and user defined interim fields. The results for Analyses set up with a calculation cannot be entered directly - the LIMS calculates it as soon as all dependent results are available

The Calculation formula references the unique Analysis Services keywords configured for them, and where applicable the keywords of Interim fields set up for the Calculation

Calculations are maintained in the LIMS Setup by authorised labmanagers, where their correct execution can also be tested. Saved Calculations are then available to be selected when configuring Methods and individual Analysis Services

Dependent results

Most results calculations will depend on a number of earlier Analysis results, and these are referenced using their unique keywords maintained on their Analysis Service pages

E.g. Total Hardness = Calcium + Magnesium, will be expressed as [Ca] + [Mg] where Ca and Mg are the keywords for the Calcium and Magnesium Analysis Services respectively

Interim Fields

Some calculations require constants, and often variable factors, used for dilution, or weights. To use these in the calculation, specify them in the Interim Fields part of the screen, giving each a title, keyword, default value and unit

E.g. Titration = [Display] * [Dilution] - the user captures the Titration volume and Dilution factor values, and the LIMS calculates the results for the Analysis using the Calculation on the same line. Volume and Dilution are the keywords for their Interim, Fields defined for the calculation

Note that the system tries to optimise the number of columns at display time, and forces the user to use the same keyword and title combinations already in use

Create or Edit a Calculation

Navigate to Calculations in the LIMS setup and select [Add Calculation] to create a new one, or to edit an existing one, click on it's title. Use the [Deactivate] if you want to decommission a calculation

Edit the calculation's title and description, and proceed to the real stuff

The Calculation tab is made up of two parts, Interim fields at the top, and the Formula itself

Interims

The Interim values can now be referenced by their keywords in the Calculation formula. Columns and entry or display fields are automatically generated by the LIMS for interim fields on ARs and Worksheets

Formula

The formula you type here will be dynamically calculated when an analysis using this calculation is displayed.

Standard mathematical operators, + - * / (), and percentages, square roots, exponentiation, and logarithmic functions  can be used on any Analysis Service or Interim Field keywords, as well as valid Python Expressions and Builtins

Enclose keywords in square brackets, [ ]

Press [save] to submit your edits 

Testing a Calculation

When the user navigates away from the formula field, the LIMS populates a list Test parameters lower down on the page, collecting the Keywords from the formula

The user may then enter values for them and when the calculation is saved, a test results is calculated and displayed from which the formula's accuracy can be determined

Applying Calculations

In Methods

Once the Calculation is configured, it can be used to configure Methods and by implication the Analysis Services usiong them. They may be tweaked further per indiviual AS

On Analysis Services

Applying Methods to Analysis Services will automatically clone the Calculations associated with the Method onto the AS where they can be tweaked one final time

Calculations can also be directly selected for Analysis Service

Runtime

Capturing Calculated results 

When Interim results are capture on ARs and WSs the final results calculation is done automatically

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Going Deep with Results Calculations

Microbiology. Sensitivity Testing

  See the formulas used to interpret organism size in Antibiotic Susceptibility and Drug Sensitivity Testing, as used in health care laboratories and applied in Bika Health

 Langelier Saturation Index, LSI, is an approximate indicator of the degree of saturation of calcium carbonate in water. Negative values are indicative of corrosion whilst positive values indicate scaling or coating

In Bika Water:

[pH]-((math.log10(100000/[CaHardnessasCaCO3]))+(math.log10(50000/[MAlkalinityasCaCO3]))+(2.6045*math.exp((-0.0108*[FieldTemp]))+(0.0144*[TtlDS]**0.4545))+(math.log10(1+((10**-(10.6-[pH]))*(1+[FieldTemp]/30))*2)))

 Worksheet wide. Correction Factors

Apply wide

It is convenient, reduce human error and faster capturing say a single Blank Correction or Dilution Factor applicable to multiple Samples in the same run, only once, and adjust their results accordingly. For that purpose collect them on a Worksheet

Configure the Calculation

In this example we have to correct all the calculated ADF Fibre results with a Blank Correction determined earlier. Routine feeds samples are dried in paper bags and an empty bag is put through the same process to determine the factor, 0.97 here

When defining the Interim fields for these factors, be sure enable them to be applied Worksheet Wide, and set an appropriate default value for it

The ADF Fibre formula looks like this:

Analysis Services

Be sure the ADF Fibre Analysis Service inherits the Calculation

Capturing Results and factoring them

With Analyses created for these Services are grouped on a Worksheet, the Correction Factor is offered for optional Worksheet wide application. Individual results may still be adjusted too

After the interim weights were captured, most likely weighed in directly from a balance, the 0.97 Blank Correction applied Worksheet wide automates 99% of the ADF Fibre results