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Biochemistry & Immunology » Immunology » ANA, dsDNA and ENA

Last update to this site: 22.7.2014
    

Lab Tests OnlineUK
ImmunologyAnti-nuclear antibody (ANA), double-stranded DNA (dsDNA) antibody, and extractable nuclear antigen (ENA) antibody

These 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.

Sample requirements: Gold cap tube (serum with separator gel)5 mL clotted blood is sufficient to perform full profile.

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
14 days
Negative <30 IU/mL
Borderline positive 30-75 IU/mL
Positive >75 IU/mL
New ranges from 31.7.13
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.

ImmunologyANA 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; screen and (if positive) profile 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.

ImmunologyAnti-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.

ImmunologyDouble-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.

ImmunologyExtractable 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)

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. Note frequent positives with negative ANA staining on indirect immunofluorescence; this is usually due to Ro52 rather than Ro60 antibody. Such results should be interpreted with caution as Ro52 does not have a strong disease association.

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.

    

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Page last amended: 24.07.2013
    

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