Allergen conversions
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.
THANKS in advance
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.
THANKS in advance
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 -
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,
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
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" :smile: -