Aliquot Volume Checks in Routing Engine

Trying to present a lab automation workflow to your peers may be a difficult task, both for the speaker but also for the audience. But not impossible. Read on, to learn how. :)

On Lab Automation

Medical laboratories have been long confronted with a dilemma: flexibility or throughput? Of course, manual processes are the most flexible. But they are also slow, consume manpower and include the risk of manual errors. In fully automated laboratory processes the situation is reversed - with the highest possible output and lower flexibility.

The challenge to new generation lab automation solutions is to find a suitable compromise between these two.

Our long-time business partner – Sysmex Europe - provides modular concepts for full EDTA management in a standardized workflow – from benchtop to automated solution, from sample entry to archiving, and with the highest efficiency on the smallest footprint.

The GLP team at RomSoft works hard to create the Routing Engine application that is meant to coordinate the entire workflow in such a lab-automation solution provided by Sysmex.

This is our colleague CS. He worked hard too, in an effort to explain to his colleagues how the aliquot volume checks are performed in Routing Engine.

This refers to a small part of the application, but still, complex enough, so he decided to use an analogy that most of us can relate to: various types of beer volumes...

Here it goes :)

Primary Samples and Secondary Tubes

When a person goes to a medical facility for a blood analysis, the lab nurse will draw what is called a total sample volume. From the total sample volume, a part will constitute the primary sample, another part will be kept for archive and the rest will be available for aliquots. The size of the primary sample is based on the number and type of tests ordered by the doctor.

So Each Sample Has an Amount of Liquid Volume

A primary sample is usually calculated depending on the type and number of tests ordered for it. Primary samples do not all have the same volume. To get a better view:

A Part of the Primary Sample Volume Is Used to Make Secondary Tubes

The aliquot module can create multiple aliquots from a primary sample. The explanation of an aliquot is a portion of the total amount of a primary sample placed in a different tube:

A Minimum and a Maximum Amount of Liquid Is Required for Each Secondary Tube (Aliquot)

From this, the following situations can derive:

(1) A primary sample can have enough liquid to fill all aliquots with the maximum amount

(2) A primary sample can have enough volume to make aliquots with volume between the minimum and maximum amount

(3) A primary sample may not have enough volume to fill all aliquots with the minimum required amount

Hang in there. There’s more...

What are Aliquot Routes and How Are They Built

Every time a route is built for a primary tube, Routing Engine will check if any area from all groups is configured with Secondary=TRUE. If Yes, Routing Engine will eventually generate a route that will contain aliquots and/or primary destinations. For the primary tube, the area with Secondary=TRUE will NOT be part of the route.

Based on ordered tests for each sample, the secondary tubes will have to be moved through a specific path (route), so the required analyses (tests) are performed.

These track areas are filtered via some normal checks to match the sample. Then, a query is performed on each track area, to see if some areas require secondary volume.

What Situations May Generate Aliquots?

Secondary tubes are generated in the following situations:

(1) The area has the Produce Secondary Tubes option set to TRUE

(2) At least one test in the area has the option Produce Secondary Tubes set to TRUE. If two area tests have this option checked, two secondary volumes are generated

(3) An area test may have an aliquot group assigned to it. Also in this case, a secondary tube is generated

(4) Finally, the Lab Information System (LIS) can request directly a secondary sample, so an aliquot is generated in this case

Main Steps

(1) Calculate available volume for aliquots

(2) Decide what action to do based on volume calculation

(3) Execute volume check action

(4) Update the sample volume (subtract volume if necessary) and tests (remove history and undo “requested for aliquot” status if aliquots could not be generated)

(5) Update remaining aliquot areas in the route

How to Calculate Volume Available for Aliquots

(1) Calculate the estimated volume needed for primary sample measurement

(2) Calculate the minimum volume needed for archive (refrigerator)

(3) Subtract from the sample volume the calculated above volumes, and the remaining volume is the available volume for aliquots. The formula goes like this:

If aliquots need to be generated, the next step is to calculate the volume amount needed/aliquot. There are two ways to do that. You can either:

a) use the aliquot definition that is included in the routed area

b) calculate based on material consumption

We'll explain in a bit.

How to Decide what Action to Execute

Method 1 – by Using Aliquots Definition

Go through each aliquot definition in the routable aliquot areas

For each aliquot definition, add the minimum and maximum volumes to the total minimum and maximum volumes

Compare the available volume for aliquots with the total minimum and maximum aliquot volumes

Based on the comparison above 3 main actions can be executed:

1. Add maximum volume to aliquots

2. Add volume between min and max for each aliquot

3. Less than minimum volume available for aliquots

In the third scenario, the primary tubes are routed out of the track area to a refill destination. Not so bad after all :)

Method 2 – Based on Material Consumption

Each test at aliquot level is performed with a certain material consumption, but also, has a certain amount of dead volume – a volume of material that cannot be used. Here's how to calculate total volume available for aliquots.

(1) Go through every aliquot group and calculate the following:

Test 1 = Material consumption1 + Dead Volume1

Test 2 = Material consumption2 + Dead Volume2

...

Test “n” = Material consumption “n” + Dead Volume “n”

(2) Add results for all tests in the aliquot group

(3) Add results for all aliquot groups

(4) Compare the available volume for aliquots with the total result

Two possible situations can occur:

(a) Available Volume for Aliquots > = Total Volume Needed for Aliquots (Total material consumption + Total dead volume) – this is the happy scenario, the tests are performed as ordered.

(b) Available Volume for Aliquots < Total Volume Needed for Aliquots (Total material consumption + Total dead volume) – this is the pessimist scenario. The tubes are taken on the output route, for refill

System Optimization

By implementing this logic, the necessary sample collection volume will be optimized at all times and unnecessary process steps will be avoided in all areas.

At all times, human intervention is allowed in order to:

  • Change list of ordered tests
  • Prioritize actions and drop the less important ones
  • Adjust aliquot volume

THE END.