Regulatory Use of

In Vivo MicroFlow Kits

Are these data accepted by regulatory agencies?

Data obtained using the MicroFlow method have been evaluated and accepted by regulatory authorities in the US and EU. These results meet OECD test guideline 474 and comply with the new ICH S2(R1) guideline.

Does this method meet OECD test guideline 474 for micronucleus assays?


The MicroFlow method meets all of the following criteria:

The guideline states, "At least 4,000 immature erythrocytes per animal should be scored for the incidence of micronucleated immature erythrocytes."

It also indicates, "Counting sufficient immature erythrocytes in the peripheral blood or bone marrow of adult animals is greatly facilitated by using an automated scoring platform."

And, "Comparative studies have shown that such methods, using appropriate calibration standards, can provide better inter- and intra-laboratory reproducibility and sensitivity than manual microscopic scoring."

Here’s how MicroFlow kits meet these criteria:

Score 4,000+ cells in less than a minute. Complete a typical study in a single day.

With Litron's MicroFlow kits, you will be using the most validated and peer-reviewed ‘automated scoring method’ available. In fact, it was the MicroFlow method that was used for the comparative studies referred to in the guideline (
Reference 1, Reference 2). This method is used by 16 of the top 20 pharma companies in the world, along with top CRO, medical device and chemical companies, among others.

Since 1999, MicroFlow kits have included ‘appropriate calibration standards’ to ensure inter- and intra-laboratory reproducibility and sensitivity.

Can Litron perform GLP-compliant analyses (MicroFlow BASIC kits)?

Litron routinely performs these analyses and complies with FDA GLP regulations and the OECD Principles of GLP. For more information, please contact us.

Does this method comply with the new ICH S2(R1) guideline?


ICH states: "Systems for automated analysis (image analysis and flow cytometry) can be used if appropriately validated…" Assays are considered validated if they meet the criteria as stated by the International Workshop on Genotoxicity Testing (IWGT): Provide % MN-RET, % MN-NCE and % RET, detect both fragments and whole chromosomes, score consistently within and between experiments, and understand how known artifacts behave in the system.

Additionally, IWGT indicates, "A number of different flow cytometric-based micronucleus assays have been developed, but at the present time the validation data are most extensive for the flow cytometric method using anti-CD71 fluorescent staining especially in terms of inter-laboratory collaborative data." [Note: This "anti-CD71" method is the MicroFlow method.]

ICH further states, "Rat blood can be used for micronucleus analysis provided methods are used to ensure analysis of the newly formed reticulocytes…and the sample size is sufficiently large to provide appropriate statistical sensitivity…"

Here’s how the MicroFlow method complies with the guideline:

The MicroFlow method meets all the criteria of IWGT. Furthermore, it is the most validated method in the world.

MicroFlow kits use the anti-CD71 method referred to above to label and score the youngest of reticulocytes, even in rat blood. Additionally, this method ensures a scoring error below the level of animal-to-animal variation by analyzing 20,000 cells per sample.