Anti Nuclear Antibodies

Update on Anti-Nuclear Antibody Testing

Anti-nuclear antibody testing by indirect immunofluorescence remains an effective method for the detection of antibodies directed against nuclear antigens. We have previously, in order to ensure appropriate turnaround time for ANA requests, stopped the routine assessment of the ANA titre, allowing more rapid processing to follow-up testing for double-stranded DNA (dsDNA) antibodies, and extractable nuclear antigen (ENA) antibodies, including Ro, La, Sm, RNP and Scl70.

The purpose of this update is to inform users of our protocol for both initial and repeat testing of ANA, dsDNA and ENA antibodies.

1. Initial Testing

  • Samples with no previous record of ANA testing will be screened using indirect immunofluorescence. We are confident that our current methodology detects clinically relevant ANA.
  • In the majority of cases, positive ANA will automatically be booked in for dsDNA and ENA testing, and additional tests such as Rheumatoid Factor, complement C3 and C4 may be added if not already requested. Results will be reported accordingly.
  • Negative ANA will NOT be processed for dsDNA and ENA testing UNLESS clinical details suggest that further screening would be clinically useful e.g. recurrent miscarriage

Repeat testing

  • Samples will be screened using indirect immunofluorescence.
  • Samples known to be ANA positive but NEGATIVE for dsDNA and ENA will NOT have dsDNA and ENA repeated unless:
  • change in clinical status is indicated on the request form
  • the last dsDNA test was more than 6 months previously
  • the last ENA test was more than 12 months previously
  • Samples known to be ANA positive and POSITIVE for dsDNA and/or ENA will ONLY have dsDNA and/or ENA repeated automatically in the following situations:
  • change in clinical status indicated on the request form
  • the last dsDNA test was more than 1 month previously/li>
  • the last ENA test was more than 12 months previously

By prior arrangement with a senior member of the medical or scientific staff, ANA titres will be performed on patients with clinical disease in whom variation in ANA titre is a good indication of variation in disease severity.

We are confident that these protocols will allow assay quality and the clinical utility of these tests to be maintained, whilst allowing the laboratory to provide the results in an efficient and timely manner.

Introduction of Immunocap 250 for Autoimmune Serology

After an extensive period of evaluation, from the beginning of February we will be using a new fully automated diagnostic system called the Immunocap 250 for the measurement of some autoantibodies. The system is produced by Phadia diagnostics who supply the ELISA based diagnostics currently used for the same assays. We have been using Immunocap technology for 2 years for allergy testing.

The autoantibody assays involved are anti-CCP, the ENA screen, specific ENAs - anti-Ro, La, RNP, Sm, Jo-1 and Scl-70 and the ANCAs; anti-MPO and Anti-Pr3. Because the same antigen preparations are used in the Immunocap that are used in the ELISAs, you should not see major changes. Indeed for those assays where we report results as positive or negative there should be no differences between results obtained by either technique. For quantitative assays i.e where we report results in arbitrary units/ml there could be differences in values because of the different detection methods. In most cases the new assay will give higher results.

We  are now going to change over to our assays for anti-MPO and anti-PR3 (18.3.08)

It is therefore extremely important for anti-MPO  and anti-Pr3, where patients are monitored using the assays, that care is taken during the change over period.  For new patients and in the future when existing patients have been monitored for a while using the new Immunocap assay there will be no problem.

However, the first result using the new assay may well be higher than that obtained with the earlier assay.

The laboratory will identify on the report forms when the change to use of the Immunocap has been made. We will also give interpretive comments on whether we believe that changes in values from the old to new assays are significant or not.

This is an important change which should markedly shorten turnaround times, improve accuracy and ease the strain on laboratory staff. If you have any questions or concerns please email Michael.Kerr@leedsth.nhs.uk or phone 01133922979.

For more details about the assays go to www.immunocap.co.uk


Page updated: 01/01/11 | Updated by: Anna McHugh

Antinuclear Antibodies