Direct measure of unconjugated bilirubin by VITROS method

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  • #467031
    PC Ho
    Participant

    VITROS method provide a direct measure on unconjugated bilirubin rather than indirect bilirubin which is by calculation (E.g. Total bil. – Direct bil.

    But in LOINC, unconjugated bil and indirect bil are same. Should we create submission?

    <a href=”https://clpmag.com/miscellaneous/article-18147/”>https://clpmag.com/miscellaneous/article-18147/</a&gt;

     

     

    #467032
    Pam Banning
    Moderator

    Hello, Before submitting, consider if the Regenstrief definitions vary from the VITROS description. There could be a dichotomy of “indirect” semantics.

    Have you checked the descriptions on the details pages? Under 1971-1 LP15449-9 Bilirubin non-glucuronidated – “…Non-glucuronidated bilirubin (also called unconjugated or indirect) is the breakdown product of heme and is not water soluble. ..Glucuronidated bilirubin (also called conjugated) is a water-soluble form of bilirubin that is made in the liver by the addition of sugar molecules to non-glucuronidated bilirubin. …A third form of bilirubin is that which is bound to albumin, and it is also known as delta bilirubin because it was originally identified based on the unexpected difference between the total bilirubin level and the level of glucuronidated plus non-glucuronidated bilirubin in some patient samples. Prior to the discovery of albumin-bound bilirubin, the term “direct” bilirubin was used as a synonym for glucuronidated bilirubin, but direct bilirubin is actually glucuronidated plus delta bilirubin (bilirubin covalently bound to albumin)”.

    Would you please check the VITROS package insert for the description of bilirubin in the Principles or Summary section for the actual target analyte.

    Thanks!

    #467033
    Pam Banning
    Moderator

    Hello, Before submitting, consider if the Regenstrief definitions vary from the VITROS description. There could be a dichotomy of “indirect” semantics.

    Have you checked the descriptions on the details pages? Under 1971-1 LP15449-9 Bilirubin non-glucuronidated – “…Non-glucuronidated bilirubin (also called unconjugated or indirect) is the breakdown product of heme and is not water soluble. ..Glucuronidated bilirubin (also called conjugated) is a water-soluble form of bilirubin that is made in the liver by the addition of sugar molecules to non-glucuronidated bilirubin. …A third form of bilirubin is that which is bound to albumin, and it is also known as delta bilirubin because it was originally identified based on the unexpected difference between the total bilirubin level and the level of glucuronidated plus non-glucuronidated bilirubin in some patient samples. Prior to the discovery of albumin-bound bilirubin, the term “direct” bilirubin was used as a synonym for glucuronidated bilirubin, but direct bilirubin is actually glucuronidated plus delta bilirubin (bilirubin covalently bound to albumin)”.

    Would you please check the VITROS package insert for the description of bilirubin in the Principles or Summary section for the actual target analyte.

    Thanks!

    #467040
    PC Ho
    Participant

    Yes, agree that they are same analyte.

    Bilirubin fractions may be measured either directly, or calculated from the results of direct measurements of other bilirubin fractions. With VITROS (Chemistry) Systems, TBIL, Bu, and Bc are directly measured. Other, more conventional bilirubin methods, especially those employing diazo chemistry, directly measure both total bilirubin and the direct bilirubin fraction (approximately equivalent to Bc), but cannot directly measure unconjugated bilirubin (Bu).

    http://vinylsocks.com/msnac/images/Bilirubin.pdf

    Would ‘Indirect bilirubin [Moles/volume] in Serum or Plasma by Direct assay’ is fine?

    Thanks.

    #467044
    Pam Banning
    Moderator

    Before you submit ‘Indirect bilirubin [Moles/volume] in Serum or Plasma by Direct assay’ to Regenstrief, please check Ortho Clinical’s customer service for their LOINC terms? The larger IVD manufacturers have been working internally to identify the correct LOINC terms for their assays. I tried to look online at their technical documents to determine how they chemically directly measure indirect (non-glucuronidated) bilirubin; couldn’t locate the package inserts for reagents on VITROS machine. Regenstrief would need that package insert as well if it’s necessary to submit.

    The method of “Direct assay” has only been assigned to LDL Cholesterol in LOINC. The submission would need to make a solid case that direct measurement in this instance is to be kept separate from values measured differently.

    Thank you for your discussion!

    Best regards,

    #467045
    PC Ho
    Participant

    Hi, thank you very much for the information.

    I find following PDF kit insert online. Would it be fine as reference?

    https://manualzz.com/doc/23391529/instructions-for-use-dbil

     

     

    #467046
    Pam Banning
    Moderator

    This PDF is for the Direct Bilirubin on the VITROS. The Principle section talks about the different types of bilirubin and states the direct bilirubin is “estimated”. That context doesn’t appear to be a measurement.  I tried the search engine within this website, but didn’t find a similar document for the indirect bilirubin.

    Thank you for performing this due diligence in your consideration. Are you in a position to get the package insert from the chemistry bench in your laboratory? There’s usually information in the reagent boxes for the instrument.

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