General

  1. Why is the Tryptase control range as wide as 9-19µg/l?

    The range can seem wide, 9-19µg/l. Though for tryptase unlike other QC samples, one have to take into account the nature of the sample. It is freeze dried and therefore the reconstitution variance will increase the total variance in a sample run (other variance factors are the other reagents, the instrument etc). The specified range will thus cover all these factors.

  2. Could help me to find the reference of the study which has establish 11,5 ng/l for the upper normal value, to which Escribano refers in his article (enclosed), and is currently accepted by many users?

    The document has been updated and is now available in a newer version (attached). The authors are both Escribano and Peter Valent and they have updated the upper normal value to 15 ng/mL (both on page 4 & 5). Please find the reference to this value attached (Schwartz 2006). When it comes to the evaluation, it is recommended that each laboratory establishes its own expected range of values but I would guess that most of the labs accepts this range or a range very close to this one. Please have in mind also that there is a study shown in the DfU for Tryptase (also attached, look at page 2) that is made in-house and to which we often refer. In this one the 95 upper percentile is 11.4 µg/l corresponding to 11.4 ng/mL but as you can see there are healthy individuals having both 15-16 µg/l and 18-19 µg/l, however the mean is 3.8µg/l.

  3. How stabile is Tryptase in whole blood?

    Sample handling according to DFU for Tryptase: preferable the sample should be centrifuged directly and then it could be stored up to a week in 2-8°C. My personal believe is that it’s okay to centrifuge the sample in the morning if it has not been done earlier, but we have no data of tryptase stability in whole blood.

  4. One of our customers using ImmunoCAP Tryptase has a question regarding the 99th percentile as there is only the 95th percentile in the DFU?

    Referring to the study shown in our Dfu for Tryptase, the 99<sup>th</sup> upper percentile for healthy individuals is 14,8 µg/l. Except for the information that is present on page 2 in the Dfu we do not have any more official documents from this study available. Though this value is calculated from the same patient material as the values shown for geometric mean and 95<sup>th</sup> upper percentile.

  5. Why is the Tryptase control range as wide as 9-19µg/l?

    The range can seem wide as the one you mention, which is 9-19µg/l. Though for tryptase unlike other QC samples, one have to take into consideration the nature of the sample. It is freeze dried and therefore the reconstitution variance will increase the total variance in a sample run (other variance factors are the other reagents, the instrument etc). The specified range will thus cover all these factors.

  6. Can Tryptase serum plasma samples be frozen for several months?

    Yes, it’s possible to store them in -20 degrees for a few months. though, if they are to be stored even longer than this, we recommend -70 degrees.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.