Anti-nuclear antibody

A raised antinuclear factor (ANF) is almost always present in SLE (80-90% - note that uraemia may render the result negative) (1).

Other conditions that are associated with a positive ANF but usually of lower titre than in SLE, include:

• systemic sclerosis (80%)
• Sjogren's syndrome (60%)
• polymyositis/dermatomyositis (30%)
• Still's disease (30%)

Also seen in:

• autoimmune chronic active hepatitis
• primary biliary cirrhosis
• infections, infective endocarditis
• fibrosing alveolitis
• drug reactions

Occasionally a positive ANF is found in normal elderly people.

Some patients are ANA positive but have antibodies which recognise different sets of nuclear proteins, termed extractable nuclear antigens (ENA)

• the commonest is anti-Ro which is usually clinically associated with photosensitivity (1)

Notes:

• low-titre ANF (titres of <=1:80) may be clinically insignificant. Higher titres may be seen in various conditions, including RA and connective tissue diseases, and sometimes in viral and chronic infections (2)

Reference:

• 1) ARC. Connective tissue disease in primary care. Hands On 2006; 9:1-5.
• 2) ARC.The approach to the patient presenting with multiple joint pain. Hands On 2012; 7(1):1-12.