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CarOvr

Russell Sargon, Product Specialist


eModule Carryover

• “CarOvr” flag is triggered when there is an extreme signal difference between two consecutive

measurements.

• The warning is an indication that a "potential micro particle carry over" within the analytical unit

may have occurred.


eModule Carryover

• How can this be?

• Each sample on e411, e601, e602, e801 have unique tips and cuvettes (cups).

• But… they all end up going to one of the two measuring cells

(single measuring cell on e411).

• Measuring Cells are effectively flow cells with each sample cocktail entering sequentially with

a wash sequence between them.

• Within the 42 second cycle time of a measuring cell*, more than 40 seconds of that is dedicated to

measuring cell scrubbing, cleaning and preparation for the next sample.

• Theoretically however, if some of the material from one sample was not cleaned out

properly, it could remain in the measuring cell and affect the next sample reading.

*e801 is 24 seconds


eModule Carryover


eModule Carryover

• Light generated (RLU) by the ECL reaction is common to all analytes being measured

• Microparticles common to all Elecsys assays

Biotin

Ruthenium

Microparticle

Antigen

1O Antibody

2O Antibody


eModule Carryover

• The alarm is generated if a sample with a very low RLU count happens to follow a sample through

the measuring cell with a very high RLU count:

• A low result sandwich assay follows a high result sandwich assay or a low result competitive

assay

• A high result competitive assay follows a high result sandwich assay or a low result

competitive assay

• if there was any sort of carryover, these are the samples that would be at risk.

• Hence the suggestion is to re-run that sample.

• In reality, no feedback about anyone re-running such a sample and getting a different result but it

is theoretically a risk.


eModule Carryover

42 16812684 Time (seconds)

RLU

(620 n

m)


eModule Carryover

42s 168s126s84s time

RLU


eModule Carryover

• “It is technically impossible to measure the micro particle carry over in a single determination of a

sample.”

• Potential micro particle carry over is calculated by a mathematical algorithm.

• Equation is confidential but it takes to account different parameters like:

• actual measured low signals in counts,

• signals of previous measurement,

• assay specific factors that are encoded in the reference data,

• CutOff Signals for qualitative assays etc.

• Carry over calculation is not required between the last sample in a rack (eg rack 1, position 5) and

first sample in the next rack (eg rack 2 position 1)

• Because an additional washing step is carried out between both pipettings.


eModule Carryover

• If seen often, it will be because of the order the tests going through a measuring cell.

• Orders tests are run depends on*:

• Host Order

• If a host is involved the e601 tests are pipetted in the same order as they are requested

by the host.

• If there is no host request but a profile run instead the pipetting order is the same as in the

list of the profile.

• If there is neither a host request nor a profile, then the pipetting order will be according to

the order of the Test Key setting from left to right.

* With exceptions


eModule Carryover

• How to minimise the occurrence of CarOvr Flags?

• look at what tests are on each measuring cell and look to swap certain assays between the cells

to break up the measuring order.

• Try switching the positions of assigned QC positions - that is, first the high control, then the low

control

• Pipetting order can be influenced the by programming new Special Washes in case of many

CarOvr alarms!


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