ANA, dsDNA and ENA

 
See below for full information on ANA screen, ANA by indirect immunofluorescence with Hep2 cellsdsDNA and ENA antibodies.
 

Alternative names, keywords

Anti-nuclear antibody, double-stranded DNA antibody, extractable nuclear antigen, anti Ro, anti La, ant Sm, anti RNP, anti Jo-1, anti Scl-70

Samples required

Clotted blood (gold cap, 5 mL tube). 5 mL is sufficient to perform full profile. Smaller tubes are available for paediatric samples.

Test indications

Anti-nuclear antibody (ANA), double-stranded DNA (dsDNA) antibody, and extractable nuclear antigen (ENA) antibody tests are predominantly used for the investigation and diagnosis of inflammatory connective tissue diseases (CTD) such as SLE, Sjogren’s Syndrome, systemic sclerosis, mixed connective tissue disease, polymyositis and dermatomyositis.

Turnaround and results reporting

Test

Turnaround

Report

ANA automated screen

7 days

Positive or negative

ANA by IIF with Hep2 cells

7 days

Positive or negative, titre and pattern.

dsDNA antibody

7 days

Negative <34.9 IU/mL

Positive >35 IU/mL

ENA antibody screen

7 days

Positive or negative

ENA antibody profile

21 days

Positive or negative for individual ENA specificities.

An interpretive comment will be added once all results have been returned.

Enquiries

Immunology

 

ANA screen

Our first-line test is now an automated ANA screening test rather than indirect immunofluorescence with Hep2 cells. This assay has much improved specificity for connective tissue diseases, but retains comparable sensitivity. The results are simply reported as positive or negative.

Where results are positive, the sample will automatically be further analysed as follows:

  • indirect immunofluorescence with Hep2 cells for ANA staining and titre,
  • dsDNA antibody,
  • ENA screen and (if positive)
  • profile of common ENA antibodies (Ro, La, Sm, Scl-70, RNP, Jo-1).

Screen-negative samples will not be analysed for dsDNA or common ENA antibodies as the results will be negative. However, it may occasionally be useful to use conventional indirect immunofluorescence in this context; please contact Dr Tarzi by email if you feel that this is required.

Repeating positives for confirmation is rarely productive, particularly within a short space of time. The laboratory will generally decline to process such requests beyond the ANA screen point. For lupus monitoring, in-house users may request dsDNA as a stand-alone test; users from Primary Care should simply state clinical information as ‘SLE’ and request ANA screen, which will trigger dsDNA antibody analysis when positive.

Anti-nuclear antibody (ANA) by indirect immunofluorescence with Hep2 cells

If indirect immunofluorescence is performed, a pattern and titre will be reported. Indirect immunofluorescence is only rarely indicated when patients are negative by ANA screen. Such requests will usually only be processed for specialists.

Double-stranded DNA (dsDNA) antibody

dsDNA antibody will be automatically measured by immunoassay when the ANA screen is positive, or as a standalone test for lupus monitoring. Positive results have a disease association with lupus, and levels have some correlation with disease activity.  Please note that false positives are rather common with modern assays. Results should be interpreted in clinical context, and also in conjunction with ANA staining: high-avidity, clinically-relevant dsDNA antibodies produce strong homogeneous patterns.

Extractable nuclear antigen (ENA) antibodies

ENA antibodies of differing specificities have particular disease associations. ANA screen-positive samples will be automatically screened for the six common ENA specificities (Ro, La, Sm, RNP, Jo-1 and Scl-70); where positive, further testing will be performed to type the ENA antibody. The ANA screen contains all of these six common specificities, therefore screen-negative samples do not need further analysis for these particular antigens.

Ro antibody
(anti-SSA)
Ro antibody is now subcategorised as Ro60 or Ro52.  Ro60 antibody is associated with SLE, cutaneous lupus and Sjogren's. A small proportions of pregnancies in the prescence of Ro antibody are complicated by neonatal lupus and congential heart block – monitoring is required.  The significance of Ro52 antibody when seen ALONE is less well-established.  An association has been reported with inflammatory myositis, however the antibody is also seen in healthy individuals; clinical correlation is needed.
La antibody
(anti-SSB)
SLE and Sjogren’s Syndrome.
Sm antibody SLE
RNP antibody
(anti-ribonucleolar protein)
Mixed connective tissue disease, but also lupus - particularly when found together with other ENA antibodies.
Scl70 antibody Primary systemic sclerosis (scleroderma).
Jo 1 antibody Polymyositis, particularly when it is associated with interstitial lung disease.