Antinuclear antibodies (ANA)

Reported as Negative or as a titre such as 1:80, 1:160 or 1:640 together with a pattern (homogeneous, speckled, nucleolar or centromere). Many UK laboratories treat 1:80 or below as within the usual range, and a low positive is found in a fair number of healthy adults in the general population, more often in women and with age. Some laboratories use a different method that reports a number or ratio instead.

Antinuclear antibodies are antibodies directed against material inside the nucleus of the body's own cells. The laboratory looks for them by adding diluted blood to cells on a slide and seeing whether the nuclei light up under a fluorescent microscope. The titre is the greatest dilution at which they still light up, so 1:640 means more antibody than 1:80. The pattern of the glow is reported too, as different patterns point towards different antibodies.

Doctors request it when looking at conditions such as lupus, scleroderma, Sjogren's syndrome and some kinds of muscle and liver inflammation, usually when someone has joint pain, rashes, mouth ulcers or unexplained symptoms affecting several parts of the body.

• Lupus, in almost everyone with it
• Scleroderma, Sjogren's syndrome and some muscle and liver autoimmune conditions
• Older age and being female, in the general population
• Some medicines, including some blood pressure, heart rhythm and antibiotic medicines
• Some long-term infections and some cancers
• Having a close relative with an autoimmune condition

• Negative is the usual finding in healthy adults; there is no lower limit
• The titre is not a good guide to how active a condition is and is not usually followed over time
• Immune-suppressing medicines lower it in some people

• Up to 1 in 5 healthy adults, particularly older women, have a low positive titre with no autoimmune condition
• A recent viral infection can produce a temporary positive
• Methods and cut-offs differ between laboratories, so a titre from one lab is not directly comparable with another's

No fasting needed. A single result is read alongside the pattern reported and the tests that follow from it (ENA and anti-dsDNA); the titre is not usually followed over time.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.