Few test results cause more worry than a positive ANA. People arrive having read that it means lupus, and they have often been carrying that fear for weeks. In most cases it does not mean lupus, and understanding why takes only a few minutes.
What the test actually measures
ANA stands for antinuclear antibody. The test looks for antibodies directed at material inside the nucleus of the body's own cells. That sounds alarming, but the immune system produces small quantities of such antibodies routinely, and the test is deliberately set to be very sensitive so that it does not miss disease.
The consequence of that sensitivity is a large number of positive results in people who are perfectly well. Depending on the cut-off used, somewhere between five and fifteen per cent of healthy adults test positive, and the proportion rises with age. It is more common in women, and it can be positive for months after a viral infection.
Why the titre matters
A positive result comes with a number, written as a ratio: 1:80, 1:160, 1:320, 1:640 and so on. That titre describes how far the blood sample could be diluted and still show a positive reaction. A higher number means more antibody.
A titre of 1:80 is weakly positive and, on its own, is usually of no consequence. Titres of 1:320 and above are more likely to be associated with a genuine autoimmune condition, particularly when the person also has symptoms. But even a high titre in someone with no symptoms and normal examination often needs nothing more than a review in a few months.
The pattern is a clue, not an answer
The laboratory also reports a pattern — homogeneous, speckled, nucleolar, centromere, and others. The pattern narrows the field. A centromere pattern raises the possibility of limited systemic sclerosis. A nucleolar pattern points towards scleroderma. A dense fine speckled pattern is, if anything, reassuring: it is associated with health rather than disease.
Patterns are read alongside everything else. No pattern makes a diagnosis by itself.
What a rheumatologist does with the result
The result is placed next to the story and the examination, and that is what decides whether anything further is needed.
- Symptoms that fit: joint swelling, a rash brought on by sunlight, mouth ulcers, hair loss, dry eyes and mouth, fingers changing colour in the cold, unexplained fever or weight loss
- Examination findings: swollen joints, a rash, nail fold changes, dry eyes
- Basic tests: blood counts, kidney function, urine for protein and blood, inflammatory markers
- Specific antibodies: anti-dsDNA, anti-Sm, anti-Ro, anti-La, anti-RNP, anti-Scl-70, anti-centromere and others, ordered according to what the picture suggests
If the symptoms, examination and follow-up tests are all normal, a positive ANA very often needs no treatment and no repeat testing. Repeating an ANA that is already known to be positive rarely adds anything, because the titre does not track disease activity.
When a positive ANA does need attention
A positive ANA matters when it comes with something else. Persistent joint swelling, a rash that flares in the sun, recurrent mouth ulcers, unexplained fever or weight loss, dry eyes and mouth, or fingers changing colour in the cold are all reasons to be assessed properly rather than reassured. Protein or blood in the urine alongside a positive ANA always needs investigating, because kidney involvement is silent in its early stages.
The practical advice
If you have been told your ANA is positive and you feel well, do not assume the worst and do not start searching for a diagnosis to fit the result. Bring the report to a consultation, together with any other results you have. In most cases the conversation ends with an explanation and no treatment at all. In the minority where it matters, having the result already in hand means the work-up starts on the right foot.
This article is general information and does not replace a consultation.