Interpretation of a Positive ANA
A positive ANA is significant only in the presence of clinically relevant symptoms. A high titre ANA can occasionally be present in normal individuals, particularly with increasing age, and under those conditions may be of no significance. An ANA may also be associated with the use of certain classes of drugs. If the ANA is considered to be clinically relevant, investigations as outlined below may be helpful in disease classification and assessment of activity
In those who have a high titre ANA with no relevant symptomatology, occassional clinical and serological review may be useful, as it is possible for the antibody to appear well before disease symptoms.
Additional Investigations for Positive ANA:
1. Antibodies to double stranded DNA:
2. Antibodies to ENA:
3. Rheumatoid factor:
Most frequently present in RA or Sjogren's Syndrome, in the latter often in combination with ANA and anti SSA and/or SSB.
5. Centromere pattern of ANA:
Highly associated with the limited (CREST) variant of scleroderma.
6. Cardiolipin antibody, Antibody tob2GP1 and Lupus inhibitor:
These antibodies mark a group of patients particularly predisposed to arterial or venous thromboembolic phenomena and recurrent miscarriages. A large proportion have SLE but in many this antibody is present without SLE or an associated ANA. In SLE its presence is also associated with CNS disease and thrombocytopenia. It is worthwhile screening for these antibodies in patients with SLE and in anyone with recurrent arterial or venous thromboembolic phenomena or recurrent miscarriages.
7. C3 and C4:
These are depressed in active SLE and rise with disease remission
8. Acute phase reactants (alpha 1 antitrypsin, fibrinogen, haptoglobin, CRP)
Elevated in active connective tissue diseases and fall with remission. These will sometime be elevated in the presence of a normal ESR.
Tend to be elevated in the presence of inflammatory diseases
For further information please contact Dr Sam Breit on 8382-7700
|Last updated 5/1/2000|