Autoimmunity

  1. Why are EliA dsDNA and Varelisa dsDNA Antibodies only against IgG and not IgG and IgM?

    IgM for dsDNA are, similar to IgG, a heterogeneous group of antibodies, some with high avidity, some with low avidity. Farr RIA is a highly specific assay for SLE which measures only IgG and IgM antibodies with high avidity. Low avidity antibodies are not found with this assay. ELISAs in general find antibodies of both, low and high avidity, which leads to a lower specificity but higher sensitivity of these assays.
    Anti-dsDNA IgM antibodies have a lower specificity than IgG, particularly when they are of low avidity. Determined by ELISA, they have been demonstrated in a variety of diseases like Sjögren's syndrome, scleroderma, MCTD and chronic active hepatitis.

    Specificity is a big aim in autoimmune diagnostics, particularly - to ensure the highest specificity possible, we do not measure IgM.

    Please find some articles to this topic here:

  2. How is the lot specific code or factor for each EliA batch determined?

    The lot specific code for each EliA batch that is used to calculate the final concentration of the test (in IU/ml, U/ml, Ratio etc) is determined at the end of the internal Quality Control procedure for the release of the newly produced EliA Well batch.

    In this QC test, amongst other results, the concentration of several predefined positive and negative Quality Control samples and the EliA Positive Control for this test is determined. For each positive sample a target value and a target range is predefined. For the negative samples a threshold level (maximum concentration) is specified. The samples are not only tested on the new batch but also on a reference batch.

    Within certain limits the factor is adjusted to best fit the combination of these different specifications on the positive and negative samples in comparison to the absolute targets and to the reference batch results. If the factor cannot be adjusted to fit one of the specifications (for example, the positive samples do not fit inside the concentration range without the blood donors being inside the maximum value) this batch cannot be released.

    The factor is needed to minimize the impact of biological, chemical, biochemical variances of the coating processes on the concentration results.

    The limitation of the factor selection is that the factor has to be higher than a certain minimum factor. This minimum factor cannot fall below this minimum because otherwise the upper limit of the measuring range given in the DfU would not be valid anymore. This minimum is defined during the tests development & validation by allowing a 20% decrease of the factor from the so called master factor determined during development. The master factor is the factor used to release the validation batches (for the product validation studies) and it is the aim of the production of subsequent batches to always stay as close as possible to this master factor.

  3. What do you know about antibodies to collagen type II?

    Collagens are components of the extracellular matrix. Collagen type II is the major collagen in articular cartilage.

    The value of the antibody determination is limited: the prevalence of anti-collagen-antibodies is relativeley low in RA-sera and they are not uncommonly found in many other diseases. Thus, specificity and sensitivity of type II anti-collagen antibodies for RA are low.

    Neither the occurrence of serum autoantibodies to native nor denatured type II collagen is specific for RA, but synovial fluids of RA patients, compared to controls, contain anti-collagen antibodies in higher frequencies and amounts. Probably, the determination of anti-collagen antibodies in synovial fluid is of greater value than in serum.

    Whenever antibodies to collagen are found, immunological cross-reactivities with C1q and fibronectin have to be taken into account.

    Since type II collagen is the predominant cartilage collagen and since type II collagen can induce an experimental arthritis in mice and rats, autoimmunity to type II collagen is of special interest in RA. However, their determination is curently more important for scientific than for diagnostic purposes.

  4. Why are the detection limits of our EliA tests so different although it is always the same curve?

    The detection limit of all EliA IgG tests is 600 µg/l as this is the highest calibration point. However, we do not give results in µg/l but in Units/ml and, thus, every limit is multiplied with the individual lot-specific factors. How this calculation is done in IDM, please see Calculation of EliA Units ».

    In our DfUs we give a minimum upper limit, specific per test. This value was calculated with the lowest lot-specific-factor, which is possible with this test. In most cases it is higher (that is why we give the upper limit of the measuring range with a ">"-sign). Please find the minimum measuring ranges given in the EliA DfUs. (see further explanation on the limit here)

    Of course, the fluorometer is able to measure higher RU-values than that of the highest calibration curve. The fluorometer measures 4-MUF in concentrations between 6.7 nM – 54 uM. This leads to signals between approximately 0.3 mV – 1900 mV or, expressed in RU, 7.5 RU – 47500 RU.

    However, as the curve is not a line but a curve with an S-shape, the values above the highest calibration point are not valid. If a sample is "above" it could be diluted until it is in the measuring range. However, for autoimmune sera this is not recommended, because they often do not dilute linearly (see linearity »).

  5. Do we have sensitivity and specificity data for all EliA analytes?

    Sensitivity and specificity data for CCP, Celikey and ANCA on EliA are available. Sometimes taken from external studies, but e.g. for ANCA we have done them internally before launch. 

    Some of the EliA analytes are markers of very rare diseases and are found only in a portion of patients. Obviously, for those markers it is not possible to define clinical sensitivity and specificity when developing such a test.
    For those analytes a technical sensitivity and specificity was evaluated by measuring samples with defined antibody specificity such as AMLI samples, CDC samples and WHO samples.
    Of course the data for technical sensitivity and specificity are not at all comparable to clinical sensitivity and specificity.

  6. What are the new conversion factors for TG and TPO on ImmunoCAP?

    The conversion factors are fixed in the software and are different for ImmunoCAP 100 vs ImmunoCAP 250:

     - TPO     16.7
     - TG       122

    ImmunoCAP 100:
     - TPO      18
     - TG       140

     For EliA there is no conversion factor, the factor is different from lot to lot and is implemented in the barcode.

  7. What are the new conversion factors for TG and TPO on ImmunoCAP?

    The conversion factors are fixed in the software and are different for ImmunoCAP 100 vs ImmunoCAP 250:

     - TPO     16.7
     - TG       122

    ImmunoCAP 100:
     - TPO      18
     - TG       140

     For EliA there is no conversion factor, the factor is different from lot to lot and is implemented in the barcode.

     

    Detection limits

    With these conversion factors you can calculate the detection limits by multiplying with 2 for the lower detection limit and with 200 for the upper detection limit.  

    Assay

    conversion factor

    detection limits

    TPO on ImmunoCAP 250

    16.7

    33.4 - 3340 IU/ml

    TG on ImmunoCAP 250

    122

    244 - 24400 IU/ml

    TPO on ImmunoCAP 100

    18

    36 - 3600 IU/ml

    TG on ImmunoCAP 100

    140

    280 - 28000 IU/ml

     

  8. Why does the EliA ANA positive control give a negative result?

    You should not dilute the ANA Control

    Please enter a request (sample id),
    then select a method (EL-G),
    then input a testname (sy),
    then press "shift enter" instead of "enter",
    then you can select "prediluted" instead of "instrument dilution" (dilution factor 100 is OK for sy)

  9. Do we have linearity data for all EliA analytes?

    All EliA assays have very broad measuring ranges.  In practice, patient samples will rarely exceed these ranges and, thus, a linearity in dilution is not often needed in practice.
    For samples which do exceed the measuring range, the actual quantitation is rarely clinically significant.  It is enough to state that the result is "greater than..."

    In all studies on linearity in EliA the specifications were set very narrowly with O/E= 0.8-1.2. It was found in a separate study (see validation plan UEVPPC03-02) that "a linearity for all tests and all sera is not achievable inside the targets O/E= 0.8-1.2 due to the unique calibrator system in ImmunoCAP".

    Statements on linearity are made under these restrictions.

    Limitations on linearity are stated in the respective DfU: "Please note that due to differing binding characteristics of the antibodies in patient samples, not all sera can be diluted linearly within the measuring range."

  10. Is EliA dsDNA suitable for the monitoring of SLE?

    dsDNA as monitoring marker is not mentioned as intended use in our DfUs. However, it has been shown in several studies, that EliA dsDNA reflects the disease activity and the involvement of the kidney. Therefore it can be used as monitoring marker.  In the following, the references are sorted by publishing data:

    Hernando M et al. Clinical Evaluation of a New Automated Anti-dsDNA Fluorescent Immunoassay.

     

    Varelisa

    EliA

    Farr

    CLIFT

    Sensitivity for SLE (%)

    44.7

    39.5

    31.6

    13.2

    Sens. for active SLE (%)

    70.8

    70.8

    66.7

    29.2

    Sens. for nephritic SLE (%)

    70.0

    55.0

    50.0

    25.0

    Specificity (%)

    82.5

    93.2

    96.1

    99.0

    • "In conclusion, the EliA™ dsDNA assay showed a very good specificity for SLE and a good sensitivity for active SLE. This assay can be used for diagnosing SLE and also for the follow-up of the disease activity."
    • "However, in clinical laboratories in which the Farr assay cannot be employed,the good sensitivity, high specificity, analytical accuracy, high degree of automation, and simplicity of execution of the EliA dsDNA test make it particularly appropriate for both the diagnosis and the monitoring of SLE patients."
    • "When compared with the ELISA, the newly developed FIA had better correlation with the serial changes of SLEDAI and C4, and was inversely correlated with the serum levels of C3. In addition, FIA had the advantage of better correlation with the occurrence of nephritis. It is worth developing this method for clinical evaluation of disease activity in SLE patients."
    • "In this retrospective study of a large cohort of patients, the new EliA dsDNA assay was demonstrated to be of slightly more diagnostic value for detecting lupus flares than the CLIFT. These data, together with the easier handling of the method, make EliA dsDNA a suitable tool for monitoring of SLE patients."
    • "CLIFT assay is likely to be accurate...; however, even though easy to perform, it is greatly operator-dependent and semiquantitative in antibody level measurement. Antibody quantitation by serum titration is considered inadequate in measuring changes in anti-dsDNA levels during disease course."
      "The ROC curves with our data showed that the EliA assay performs better than the Farrzyme dsDNA test."
    • "As regards SLE clinical monitoring, the assays gave meaningful results, generally concordant one to the other in realtion to global activity and organ specific involvement, mostly renal and haematologic, as expected. In addition, antibody levels correlated with global disease activity score measured by ECLAM score, in an independent manner."
  11. ENA vs ANA definition

    Definition ANA

    ANA (antinuclear ANTIBODIES) classically are detected by immunofluorescence. Thus they are named after their place where they bind the antigens - in the nucleus. It is a general name for all antibodies which react with nuclear antigens.
    But in the practical termination of doctors ANA also can bind antigens in the cytoplasm (like Jo-1 and Rib-P).

    Definition ENA

    ENA (extractable nuclear ANTIGENS) are a wide spectrum of nuclear antigens, which can be eluated easily by salt extraction. ENA are usually commercially available rabbit or calf thymus extract (CTE). They commonly has been used for Ouchterlony assays, but can be used also in other methods than immunodiffusion. ENA for ELISA or RIA are also commercially available, but their purity is not known. Usually, recombinant nuclear antigens are not called ENA.

    The diagnostically most important ENAs are the Sm antigens. Other ENAs are U1-snRNP, SS-A/Ro, SS-B/La, Jo-1, Scl-70, PM-1, Mi and Ku.

    DNA, centromere proteins and histones don't belong to the group of ENAs, but are nuclear antigens.

    ENA or ANA

    In summary the term ENA is used for a special group of nuclear antigens, defined by the method of purification. ANA can bind to ENA but also to other nuclear antigens.

    I think the term "ANA Screen" is more correct than "ENA Screen" (even if we used only ENA for coating), as we mostly use recombinant antigens, not extracted antigens from animal tissue. (Besides we screen for antibodies, not for antigens).

    More difficult is the situation in France or other countries were the term ANA is only used for ANA detected by immunofluorescence. The laboratory is obliged to use immunofluroescence if the physician asks for an ANA Screen. Only if ENA is asked for, the laboratory has the possibility to use ELISA.

  12. Why is UniCAP TG not included in NEQAS?

    TG antibodies are not included any more because NEQAS has the opinion that measuring TPO alone is sufficient and TG doesn't add any further information. Therefore TG is almost not measured any more in the UK.

    This is the general international opinion of most of the opinion leaders. However, there are still some hints in the literature, that TG Abs is a valid marker.

  13. What is the clinical association of antibodies to the different U1 antigens?

    Anti-U1 RNP antibodies are found in about 30 to 40 % of patients with SLE. These antibodies may occur alone but are often present in conjunction with other specificities. Although these antibodies may occur alone in SLE, the converse finding, patients with anti-Sm who lack anti-RNP, is unusual.

    The major clinical association of anti-U1 RNP antibodies is with mixed connective tissue disease (MCTD) where they typically occur in high titers and are not associated with other specificities. Indeed, this illness is defined by the presence of these antibodies.

    Anti-U1 RNP antibodies may also occur in a small fraction of patients with Sjögren¿s syndrome, rheumatoid arthritis, scleroderma, and polymyositis.

    Longitudinal studies have indicated that anti-U1 RNP antibody titers vary over time, but it is uncertain whether these levels reflect underlying disease activity.

    Different antibody populations

    The three unique proteins of U1 snRNP, 70 kD, A, and C, do not share known cross-reactive epitopes, and are recognized by at least three separate antibody populations, which may occur together or singly in a given patient. In other words, all three antibodies contribute to the anti-U1 RNP response.

    When patient sera are grouped and examined irrespective of disease, anti-70kD, anti-A and anti-C antibodies appear to have similar prevalences.

    Anti-70 kD U1 RNP
    In general, anti-70 kD antibodies are found in around 12 % of patients with SLE.

    As few as 8% to 21%, up to 85% of preselected anti-U1 positive SLE patients will have anti-70 kD antibodies, depending on the sensitivity of the assay. Anti-70 kD occur in 75 to 95 % of patients with MCTD (who are, per definition, preselected as anti-U1 RNP positive).

    When patients with MCTD and SLE are grouped together, anti-70 kD antibodies appear to correlate with myositis, esophageal hypomotility, Raynaud¿s phenomenon, lack of nephritis, and the HLA-DR4 phenotype.

    Anti-A RNP
    Among patients selected because they have SLE, anti-A antibodies appear to be twice as common as anti-70 kD antibodies, appearing in approximately 23% of such patients overall, or in approximately 75% of preselected anti-U1 positive SLE patients.

    Presently, it is unclear, whether anti-A antibodies are associated with specific disease manifestations.

    Anti-C RNP
    Clinical associations of these antibodies have not been recognized as yet.

  14. What is the Wo80 standard and how can kits have different cut-offs although they are standardised against the same international standard?

    The Wo/80 Standard is the international standard of the WHO for measuring of anti-dsDNA antibodies. All anti-dsDNA kits which are calibrated against this standard, do use Internation Units (IU/ml) instead of arbitrary units (which is the common quantitative unit in autoantibody testing, because only in very few cases a standard is available).

    The Wo/80 is human serum with dsDNA antibodies. The standard has existed since 1985 and is marketed by the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service (CBL) in Amsterdam.

    All kits which are calibrated against the Wo/80 Standard have to find it at a level of 100 IU/ml.
    Both Varelisa dsDNA Antibody test and EliA dsDNA are calibrated against the Wo/80 standard.

    However, both kits have different cut-offs: EliA dsDNA at 15 IU/ml and Varelisa dsDNA Antibodies at 55 IU/ml. This is due to the high heterogeneity of dsDNA antibodies: Some patients make low affinity antibodies that do not bind tightly, do not form very stable complexes or the complex can be separated by minor changes in temperature, ionic strength, pH etc.
    Some patients make low affinity antibodies that do not bind tightly AND high affinity antibodies that do bind tightly.

    What is the result? Every sample has the potential to behave differently from:

    • every other sample
    • samples at different times from a patient
    • any standard
    • any quality control material
    • any quality assurance material

    This results in a huge variability in results between

    • labs
    • methods
    • samples
    • concentrations

    Thus, although all tests are standardised against Wo80 and give international units, the result can vary widely between different patient samples. In quality assessment schemes it can be seen that one sample can produce very different results, depending on the method used.

  15. Do we have any studies of the interference about Lipemic, hemolyzed or microbially contaminated samples poor results and not applicability?

    We are doing interference studies each time when we develop a new test. We use an interference kit from Japan, measuring bilirubin F and C, hemoglobin, chyle and rheumatoid factor. We test normally 2 positive samples with concentration level around the cutoff and 1 medium to high positive sample. The data are available for all tests. However, we never saw any interference in one of our tests.

    However, as we never can measure all kinds of samples, we put this warning of possible poor results in all our DfUs.

    Poor means bad and can go in every direction. It depends which part of the test reacts with the substance. As we have never seen these poor results we have no personal experience.

  16. Why do some samples not give linear results when diluted (particularly in Celikey IgG)?

     The immune response in the human body is polyclonal. There are different B-cells producing slightly different antibodies with different avidity and affinity and which may even react with different epitopes on the same antigen. If you dilute a sample, the different avidities and affinities may affect their frequency of binding. The more the serum contains specific antibodies and the more it is positive for the respective parameter, the more these effects of different antibody types may be pronounced. Thus, a relatively small concentration of high avidity antibodies may give the same result in a diluted sample as a big amount of low avidity antibodies in an undiluted sample will give. Because real samples contain a mixture of such antibodies, they will not necessarily behave linearly.

     In some tests such as tTG IgG assays there is an additional reason for possible non-linearity: most sera which are positive in this test are also positive for tTG IgA and quite often these IgA antibodies against the same antigen may be present in high amounts. These IgA antibodies compete with the tTG IgG antibodies for the binding to the antigen and, thus, occupy most of the available binding sites. The higher the avidity of the IgA antibodies is, the more this effect occurs.

     If the sample is diluted the tTG IgA antibodies are diluted in the same degree and more binding sites can be accessed by the tTG IgG antibodies. For some samples, this can even lead to higher results for tTG IgG in diluted samples than in non-diluted ones. In samples with very high antibody concentration it may also happen that the antigen coated to the wells is not sufficient to bind all tTG antibodies (IgG and IgA). Even if the sample is diluted there may still be enough antibodies to bind all antigens.

     Result in both cases: the sample does not behave linearly.

     EliA Celikey IgG is evaluated for a sample dilution of 1:100. If a sample is diluted more with diluent, the matrix of the antibody containing sample will change. The more it is diluted the more it will differ from the original, physiological environment of the antibodies and will be more artificial with every dilution step. This may result in the binding features of the tTG antibodies changing which would lead to non-expected results. Result: the sample does not behave linearly.

  17. Is it often seen, that La antibodies are positive, but Ro abs are negative?

    Anti-SS-B/La antibodies are found almost always in combination with anti-SS-A/Ro antibodies and in 10 to 20 % of cases the anti-SS-A/Ro antibodies are found solely. (1) Neonatal lupus erythematosus (NLE) rarely occurs in the absence of Ro antibody; only four cases of La antibody positivity in the absence of Ro antibody have been reported. However, three of the four mothers were positive for both anti-Ro and anti-La antibodies. It is extremely rare to find La antibody in the absence of Ro antibody in both mother and infant. One case is described in the article of Neidenbach et al. (2) The significance of the finding of solely La antibody positivity is unknown, but it does support observations by Provost et al. that La antibody is significant in the pathogenesis of NLE. (2) Franceschini et al. describe an infant with cutaneous lupus lesions who, along with his mother, was positive for antibodies to La and negative for anti-Ro and anti-U1 RNP antibodies. (3) In 1989 Buyon et al. found, that antibodies to the 48-kD La antigen and its 43-kD degradation product were both found in the highest prevalence and were the antibody species most strongly associated with NLE. The individuals without detectable antibodies either to 52- or 60-kD Ro antigens each had very high levels of antibodies that reacted with the La polypeptides.

     

    References:
    (1) Humbel RL (1998) Autoantikörper und Autoimmunerkrankungen, Elsevier, Amsterdam

    (2) Neidenbach PJ, Sahn, EE (1993) La (SS-B)-positive neonatal lupus erythematosus: Report of a case with unusual features. J Am Acad Dermatol 29, 848-852

    (3) Franceschini F, Bertoli MT, Martinelli M et al. (1990) The neonatal lupus erythematosus associated with isolated La(SSB) antibodies. J Rheumatol 17, 415-417

    (4) Buyon et al. (1989) Acquired Congenital Heart Block. J Clin Invest 84, 627-634 

    References:
    (1) Humbel RL (1998) Autoantikörper und Autoimmunerkrankungen, Elsevier, Amsterdam

    (2) Neidenbach PJ, Sahn, EE (1993) La (SS-B)-positive neonatal lupus erythematosus: Report of a case with unusual features. J Am Acad Dermatol 29, 848-852

    (3) Franceschini F, Bertoli MT, Martinelli M et al. (1990) The neonatal lupus erythematosus associated with isolated La(SSB) antibodies. J Rheumatol 17, 415-417

    (4) Buyon et al. (1989) Acquired Congenital Heart Block. J Clin Invest 84, 627-634

  18. Why don't we put Histones on EliA?

    Reasons for discontinuing Histone Abs:

    1. The right antigen is not known
    2. Histone Abs are not specific for any disease
    3. Diagnosis of drug-induced lupus can be made without histone antibodies
    4. Positivity for AHA is often misinterpreted.

    Details to these points see below. Further arguments are:

    1. Patient-to-patient variability is very high
    2. Association with disease activity in lupus or RA is possible but not usable for monitoring
    3. No association with specific manifestations
    4. A negative result for IgG antihistone antibodies does not exclude a diagnosis of drug-induced lupus or SLE

    1. The right antigen is not known

    For drug induced lupus it is said, that antihistone antibodies (AHA) react with all histones, but have a predominant specificity to H1 and H2B. The classical ELISA for AHA is coated with a mixture of all histones. It is not known, whether those are coated as complex or as single proteins or if the proteins are in a natural or denatured conformation.

    Some authors claim that antibodies against the (H2A-H2B)-DNA complex are the "real" markers for drug-induced lupus (DIL). But what is the difference of this complex to the nucleosome? Nucleosomal antibodies are said to be highly specific for SLE, not for DIL. The dimer H2A-H2B seems to much less specific and sensitive for DIL. DNA lacks here - but DNA-antibodies are very specific markers for SLE and are an exclusion criterion for DIL.

    On the congress in Geneva in February, one lecturer spoke about H1 antibodies being very specific for SLE. But if they are the typical antigen for histone antibodies and these are typical for DIL ¿ than what is the truth?

    2. Histone antibodies are not specific for any disease

    Histone Abs belong to the most common ANA. In some connective tissue diseases they occur regularly and in a high amount:

    -  SLE                                         50-70%
    -  Active SLE                                80%
    -  Rheumatoid arthritis (RA)          15%
    -  Juv. chronic arthritis (JCA)          50-70%
    -  Sjögren`s Syndrome                  23%
    -  Polymyositis/Dermatomyositis    17%

    But they occur also often in Felty's syndrome, diffuse cutaneous scleroderma, systemic sclerosis, autoimmune disorders of the liver, some neurological diseases, infections and even in asymptomatic relatives of SLE-patients.

    And of course they are found in drug induced lupus, but dependent on which drug the lupus induced, the frequency of histone abs varies:

    -  Procainamide induced lupus         85-95%
    -  Quinidine induced lupus               50%
    -  Hydralazine induced lupus            approx 30%       

    3. Diagnosis of drug-induced lupus is more accurate without measuring histone antibodies

    The diagnosis of DIL should base on the following criteria:

    • Signs or symptoms of SLE in a patient on lupus-inducing drug therapy
    • No multisystem involvement or serious CNS or renal involvement
    • Improvement and resolution of symptoms within days to weeks of discontinuing drug therapy
    • No dsDNA antibodies (no Sm, RNP, Ro, La)
    • No hypercomplementemia

    4. Positivity for AHA is often misinterpreted

    AHA often are understood as markers for SLE and drug-induced lupus. But because histone Abs can occur in a wide variety of diseases and even in healthy individuals, the positive result is more misleading than helpful.

  19. Why is the EliA upper limit of the measuring range given with ">"?

    The upper limit of the measuring range for EliA is lot-specific!

     The measuring range for EliA is limited at the upper end (usually) by the highest calibrator:

    EliA IgG System: CAL-6 is 600µg/l
    EliA IgA System: CAL-6 is 80µg/l
    EliA IgM System: CAL-6 is 1000µg/l
    EliA Calprotectin System: CAL-6 is 750ng/ml

    But how does this transfer to the measuring range for a specific product in EliA Units?

    For the calculation of the concentration in EliA Units (full explanation see here) the lot-specific factor is relevant. Thus, the actual upper limit for an EliA test is lot-specific, depending on the value of the factor. But we are required to give a limit in the DfU, and we also want to guarantee a certain measuring range. Therefore, we have limits in which the lot-specific factor can vary. In this case, we have the general limit that the lot specific factor can only decrease 20% from the usual lot-specific factor (master factor, defined during validation). The limit in the DfU is calculated on this lowest allowed lot factor, because it means that we cannot relese any batch for which the upper limit of the measuring range will be lower than this limit in the DfU. That is also why we give the limit in the DfU with ">" because usually the detection limit for any batch at the customer will be higher than this value.

    Example:

    EliA Ro
    Master factor: 0.50
    Lowest allowed lot-specific factor: 0.40

    detection limit in the DfU: ">240 U/ml"
    (600 µg/l x 0.40 = 240 U/ml)

    detection limit for a batch with factor 0.48: 288 U/ml
    (600 µg/l x 0.48 = 288 U/ml)
    So, results between 240 and 288 will still be given with actual, correct, numeric concentration results. Only results above 288 U/ml will be reported as "ABOVE".

     

  20. Where can I find a list of the FDA registered products?

    On Dianet:

    Sites: Germany

    left side: "QR"

    QR: "Registrations"

    click on "USA"

  21. Where can I find a list with sensitivities and specificities of the EliA products?

    On Dianet:

    Sites: Germany

    Autoimmunity: Our Products

    click on the first Excelspreadsheet under Overview List

  22. Do some patients have anti-streptavidin antibodies? And regarding streptavidin-coated EliA tests: Is there a reaction between anti-streptavidin antibodies in the sera of patients and does this effect influence the test result?

    Yes there are patients with anti-streptavidin antibodies. And this also may be a reason for positive CTD-Scree test results but negative Symphony results.

    Several tests are streptavidin-coated (CTD Screen, SmDp, Fib, Pm-Scl, Mi-2, PCNA, RNA Pol III, Scl-70s, PR3s, MPOs). Because the dilutions for this tests are always more than 1:10 (which means also an increased dilution of the streptavidin antibodies) there is in genaral no great influence, merely a slight increase of the result can be an implication of streptavidin antibodies.

  23. Are there patients with anti-streptavidin antibodies in their sera? And regarding streptavidin-coated tests: do unspecific reactions between these antibodies and the streptavidin influence the test results?

    Yes there are patients with anti-streptavidin antibodies. And this also may be a reason for positive CTD-Screen test results but negative Symphony results.

    Several tests are streptavidin-coated (CTD Screen, SmDp, Fib, Pm-Scl, Mi-2, PCNA, RNA Pol III, Scl-70s, PR3s, MPOs). Because the dilutions for this tests are always more than 1:10 (which means also an increased dilution of the streptavidin antibodies) there is in general no great influence, merely a slight increase of the results can be an implication of streptavidin antibodies.

  24. Do the EliA beta 2-Glycoprotein tests include domain I of beta 2-Glycoprotein I? Is especially domain I of beta 2-Glycoprotein I a new risk marker?

    Yes, domain I of beta 2-Glycoprotein I (beta 2-GPI) is also included in our test, like all the other protein domains of this protein. For this tests we use human purified beta 2-GPI as antigen, so all the sufficient domains are comprised.

    Inova advertised domain I as a risk marker for thrombosis and to a lesser extent for pregnancy complications in patients suffering from APS (Mahler M., Autoimmne Rev. 2012,  12(2):313-7). But the opinion of our KOL's is, that there is no sufficient sensitivity of domain I for use in routine diagnostics.

  25. Please explain the number printed on the DFU to me: what's the meaning of each digit in detail?

    Here you have an example: the number printed on the DFU of EliA TG for Phadia 250 and the corresponding explanation:

    250-5642 -01 / UK

    250: Phadia instrument

    5642: product

    01: version of DFU

    UK: country

     

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