Reagent Handling

[RR1]

Please could you give me your views on the following:

If a blood grouping (or any) reagent insert states that the reagent cannot be left on an analyser continuously for >72 hrs.

a) is it acceptable to place the reagent back into a fridge every 12 hrs and continue to use this over a long period (of 4-8 weeks) ?

if it is acceptable to perform a) , why would the reagent manufacturer give a maximum 72 hr time period on the reagent ?

many thanks

Rashmi

rashmirook@hotmail.com

[David Saikin]

I think the buzz word is "continuously" . . . which to me means 72 hrs on the instrument, not on again/off again.

[RR1]

Thanks David- but even if the reagent is left 8-12 hrs at room temperature and rotated over a few weeks, there must be deterioration in potency.

Also we are then introducing repeated microbial contamination by the analyser probe- into the reagent bottle, this must have a detrimental effect on the reagent by the time we get to the final few mls.

I suppose the answer would be to validate some ABO annd Rh D antisera by performing titres and cultures over the span of use. Has anyone does this, or have any suggestions ?

Many thanks

Rashmi

rashmirook@hotmail.com

[Lcsmrz]

This is a good question to ask the vendor. If studies have been performed to verify its perfromance with discontinuous storage on the analyzer, than they can send you a letter stating so. My guess is that they have not, given the problems with such a complicated validation.

Some analyzers have a reagent timer, allowing you to start it on placement and stop it on removal.

[RR1]

Thanks for that, it would be a very complex validation. Ultimately we need to use some common sense with reagent handling. Reagents will generally go 'off' if stored and handled incorrectly.

There are automation manufacturers and suppliers promoting equipmentbased on 'cost-savings'- which may be to do with using basic antisera for prolonged periods. These companies need to to show documented evidence that room temperature storage, with repeated exposure to potentially contaminated sample/ reagent probes does not cause avidity and contamination of their reagents.

Sometimes we have to question what manufacturers and suppliers tell us- and we all need to ensure good practices are adhered to - especially in regards to our critical ABO and D typing reagents, of which the quality must always be maintained to the highest standards.

[JHH1999]

Reagent manufacturers must have data to fully support any claims in their package insert. They should have stability data over the shelf-life of the product. If the manufacturer really covered all the bases they should also have data on some failure mode testing. For example; using the same reagent container over multiple days to show that it works, keeping the reagent at room temperature for extended time and even shipping validation to prove the product can handle temperature excursions during shipment. Contacting them to see if they have additional data may not be a bad idea. They cannot put everything they have done in the package insert or it would be a book.

Most reagents have a preservative in them to help prevent microbial contaimination. For blood grouping reagents that is traditionally sodium azide. This preservative is very effective in microbial control.

We also need to rely on the controls that are run. They are run for a good reason. Expected results obtained with proper postive and negative controls verify reagents are performing as expected.

[RR1]

If there have been reports of bacterial contamination of D-typing reagents, after being left on analysers for a couple of weeks- would you not question the reagent handling , especially if companies say that these reagents can be repeatedly moved on and off the analysers until their expiry date?

With reference to controls, this should detect potential problems- but it depends on how often you run them.

Thanks!

[JHH1999]

I would suspect improper handling of reagents if bacteria contaimination was actually proven. In the US the FDA requires that licensed blood grouping reagents undergo preservative effectiveness testing. This is usually done according to USP standards where the product is challenged with 1X10 6 concentration of microorganisms. A colony count is then performed over a 28 day period to determine log reduction of viable organisms.

The preservative helps control organism growth over the shelf life of the product since these reagents would be considered a multi-dose device. I think it would take a considerable amount of bacterial contamination to make an Anti-D reagent stop working since they are usually very potent reagents.

For manual typing reagents I go with running controls daily. On automated instruments I would rely on the instrument manufacturer's recommendation for control frequency.

[RR1]

I'm more concerned with anti-D reagent giving false positive reactions if contaminated with bacteria (could this have a Lectin -like effect on the reagent ?) .

Currently we run our controls twice a day (which is greater than the manufacturers recommendations), but a recently inspected lab in the UK- was asked that if a control fails- did they repeat/ question the validity of ALL samples tested prior to the failed controls. This would involve possibly re-testing a justified number (or all?).

Thanks for the info!

Rashmi

[JHH1999]

I have never heard of bacterial contamination causing spontaneous agglutination or something like polyagglutination, but I guess anything is possible depending on the type of microorganism. From a quality point of view, the validity of any test results obtained after a control fails should be questioned.

[RR1]

Yes I agree, but they are questionning the validity of all test results prior to the failed control.

[JHH1999]

If both controls were run on the same day I would also question the results obtained before the second control failed. There would need to be more investigation as to why the controls failed to be able to evaluate previous test results.

One could argue the need to run controls at the begining and the end of a run when performing automated testing. As long as both sets of controls are acceptable there should be no question to the accuracy of the results. I have seen this done for infectious disease testing.