Loinc – problems

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  • #16239
    tberger
    Participant

    Hello,

    I carefully read the User Guide (ok the german translation 😉 ), but there are still some questions open.

    If I correctly understood the whole DB u only make a difference between Serum, Plasma, Liquor, … .
    -) But what should I do if I have Analyts eg. D-Dimer. We can measure it from Citratplasma and from Li-Heparinplasma/K²- K³-EDTA, the problem is that the result from the Citrat is 19% lower (its in the package insert)
    Until now I couldnt find an segmentation that solve that problem.

    -) Units
    There are many Analyts like 1751-7 which have a certain Unit, in this case g/dL
    On the other hand there are Analyts without an unit like 1747-5.
    So should it be my aim to generalize and give Albumin which are possibly messured in µmol/L, g/L or mg/L the same LOINC Code or should I request a new Loinc for each Unit thats not available in the set of Codes.

    -) International Units VS Units
    there are many Analyts eg. 19176-7 compared to 19171-8 or 44910-8 where u use in the same analyt one time the IU/ml and the other time U/ml.
    Is it possible that in the Loinc Code u use the International Units as an pseudonym for Units? At least in many cases.
    http://en.wikipedia.org/wiki/International_units

    The IU should not be confused with the enzyme unit, also known as the International unit of enzyme activity and abbreviated as U.

    thank you for your help!
    with best regards
    Thomas

    #16560
    kmercer
    Participant

    I’m not certain if I understand your questions completely, but here’s my response.

    1. Anticoagulant: LOINC does not differentiate the type of anticoagulant used.
    2. Units: Both of the terms that you have given have example units. You would use the same LOINC code for all mass/volume (g/L, mg/dL, etc.) and a different one for substance/volume (umol/L).
    3. IU vs U: In theory, International units (IU) should be used for tests that are compared to a WHO standard, but the reality is that most of the time labs just report units/volume. Conversely, we’ve noted that some labs report International units/volume for everything.

    Hope this helps.

    #16558
    tberger
    Participant

    hi kmercer,

    thank you for responsing, it was really a help.

    We are just very astonished that the loinc code doesn´t support a differentiation between the anticoagulants, I mean there are really a lot of Analyts with +-10 to 12% difference and still a few with up to +-19%.

    #16559
    Dirk Bakkeren
    Participant

    Dear Thomas,

    I understand your problem with the limited number of ‘systems’ (sample materials) to select from. I had the same hesitation when starting to know LOINC. However, every coding system has to deal with the problem of granularity. With granularity I mean the number of different codes that are used to distinguish results from the same component from slightly different materials. Lab people like you and me are use to appreciate these differences, but for docters the results, even ± 10%, often mean the same. We use different codes to tell our information systems whether results may be presented/compared together (on the same row in an cumulative report) or not.
    In The Netherlands we are working on an Dutch susbset of LOINC (and additional SNOMED CT) codes (as not all codes are relevant to us). The LOINC short and long names in the Dutch subset will be translated in the near future.
    In an IHE-NL Lab working group we defined a complete HL7 3.0 CDA message structure (from test request to result communication) for which the LOINC code together with the actual units (like mmol/l) and reference range are the pay load. In this message there are additional (optional) fields reserved to give more detailed information about the exact sample material and the laboratory method used. This information must alway be in accordance with information inherant to the chose LOINC code! This extra information is more important for inter-lab communication then for result communication to docters.

    There is another problem that is not yet covered, that is the problem of method calibration. It is possible that two labs perform the same assay, use the same LOINC code, but have their methods calibrated differently. We have a couple of examples in The Netherland. Most labs have their enzymes (IFCC methods) calibrated using a very good commutable enzym calibrator (KAL 2000 SKML, Nijmegen, http://www.skml.nl). However, as we are close to the Belgium border, enzyme assays performed in Belgium clinical chemistry labs may have the same LOINC code and units, but at the same time have different reference values, as these assays are calibrated using a different calibration method (i.e. using the molar extinction coeffient of the reaction product). These differences have be solved when exchanging results. Selection of LOINC codes alone is not always enough! The actual chosen units are important (esp. with endocrine assays) as are the calibration method or actual reference ranges (as these also change with a different calibration).

    Dirk Bakkeren

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