# Allergen conversions

6 replies to this topic

### #1 AJL

AJL

• IFSQN Senior
• 297 posts
• 18 thanks
36
Excellent

• Germany

• Gender:Male

Posted 18 June 2022 - 08:41 PM

Hi!

Hoping from some math brains to pop up here and save me!

I have found some great allergen (gluten) swabs with detection limit of 4ug/25cm2.

When I sent the swabs in to the lab to get a validation, the units come back in g/L.

How do I convert so I end up with the same units? It would just be great to know how close to the LOD I got to with the positive result. The lower the better, then I can see that my swabs work close to the LOD.

### #2 Charles.C

Charles.C

• IFSQN Moderator
• 20,537 posts
• 5627 thanks
1,532
Excellent

• Earth

• Gender:Male
• Interests:SF
TV
Movies

Posted 19 June 2022 - 07:35 AM

Hi!

Hoping from some math brains to pop up here and save me!

I have found some great allergen (gluten) swabs with detection limit of 4ug/25cm2.

When I sent the swabs in to the lab to get a validation, the units come back in g/L.

How do I convert so I end up with the same units? It would just be great to know how close to the LOD I got to with the positive result. The lower the better, then I can see that my swabs work close to the LOD.

Hi AJL,

I assume the "swab" delivered to lab was a "swab"  immersed in a liquid (S).

I assume swabbed area was 25cm2

I assume "ug" = microgram

volume of S = X  litre

lab result = Y g/litre

Relevant allergen (gluten) in swab = G

Then (With a few assumptions) -

Quantity of G associated with swabbing area of 25cm2  = XY grams = XY x  106 ug

Can compare to 4 ug

JFI this example might also intrigue you -

https://www.factssa....sked-questions/

Kind Regards,

Charles.C

 Thanked by 2 Members:

### #3 AJL

AJL

• IFSQN Senior
• 297 posts
• 18 thanks
36
Excellent

• Germany

• Gender:Male

Posted 19 June 2022 - 09:36 AM

Thanks Charles,
The swab was not immersed in liquid, but the swab was slightly moistened. The lab must have immersed in a standard amount of extraction solution, which I do not know.
Yes ug=mcg.
Yes swabbed area is 25cm2.
I assume this means that I cannot complete the conversion unless I know the amount of liquid which the lab used for the submersion?
I am not impressed by the units they used, I would have preferred g/swab. I will read the link you shared. Thank you!!

### #4 Tony-C

Tony-C

• IFSQN Fellow
• 4,004 posts
• 1224 thanks
529
Excellent

• United Kingdom

• Gender:Male
• Location:World
• Interests:My main interests are sports particularly football, pool, scuba diving, skiing and ten pin bowling.

Posted 20 June 2022 - 03:06 AM

Hi AJL,

I would ask the Laboratory for a copy of their test method, that should explain their reporting. Post it here if it doesn't make sense.

Kind regards,

Tony

### #5 AJL

AJL

• IFSQN Senior
• 297 posts
• 18 thanks
36
Excellent

• Germany

• Gender:Male

Posted 20 June 2022 - 03:41 AM

Thanks Tony 👍 good point

### #6 Charles.C

Charles.C

• IFSQN Moderator
• 20,537 posts
• 5627 thanks
1,532
Excellent

• Earth

• Gender:Male
• Interests:SF
TV
Movies

Posted 20 June 2022 - 07:32 AM

Thanks Charles,
The swab was not immersed in liquid, but the swab was slightly moistened. The lab must have immersed in a standard amount of extraction solution, which I do not know.
Yes ug=mcg.
Yes swabbed area is 25cm2.
I assume this means that I cannot complete the conversion unless I know the amount of liquid which the lab used for the submersion?
I am not impressed by the units they used, I would have preferred g/swab. I will read the link you shared. Thank you!!

Hi AJL,

Re ^^^(red) - Yes, you will presumably need some feedback from Lab. The quantitative process is not exactly "simple".

Are you using a particular commercial Product/testkit ?  If so, which one ? (This should detail how to proceed or offer technical backup on request).

The ELISA methodology typically requires extraction of the allergenic protein from the swab. The extract is then sampled/analysed.

JFI, I noticed this caveat for one commercial system -

How long can sample extracts and swabs be stored before testing?
Swabs can be stored for up to 24 hours at 4°C after sample collection provided they have not been extracted yet. Once extracted, samples from swabs should be evaluated within 4 hours. All other sample extracts should also be tested within 4 hours.

PS - you may also find this Production-oriented illustration of interest although (a) the included  VITAL-interpreted material likely has geographically restricted useability and (b) note the words "extreme" /  "homogeneously"   -

https://www.zeulab.c...l-de-alergenos/

Kind Regards,

Charles.C

### #7 AJL

AJL

• IFSQN Senior
• 297 posts
• 18 thanks
36
Excellent

• Germany

• Gender:Male

Posted 20 June 2022 - 07:51 AM

I am using Römer labs rapid test kit, the lab I assume is using Elisa, with result in g/L

 Thanked by 1 Member: