|Description:||Antibody to the La antigen is detected in approximately 15% of SLE patients. It is also detected in a higher percentage (60-70%) of the sera of patients with Primary Sjögrens syndrome. In both cases it is almost always associated with anti-Ro. Except for the overlapping presence of SS in patients with SLE, there do not appear to be any distinguishing clinical features which are associated with the presence of anti-La.Anti-La antibodies give a fine nuclear speckled pattern of staining on Hep2 cells. However this staining is often obscured by a homogeneous pattern due to other specificities of anti-nuclear antibody in the same sera. La antigen is associated with Ro in specific small ribonucleoprotein complexes. Although it is predominantly located in the nucleus the La protein has a role in transport of some RNAs into the cytoplasm. Autoantibodies recognise conformational and linear epitopes throughout the molecule.|
|Indication:||Autoantibody associated with SLE or Sjögrens syndrome. Important in pregnancy where there is suspicion of congenital heart block.|
|Interpretation:||Antibodies to La are found in 25-80% of patients with primary Sjögrens syndrome particularly those with hyper-gammaglobulinaemia, extra glandular manifestations, especially vasculitis and cytopaenias. 20-90% of patients with secondary Sjögrens have antibodies to La. It is uncommon for patients with Sjögrens syndrome not to have anti-La antibodies.The 5-15% of patients with SLE having anti-La antibodies usually are those with associated Sjögrens syndrome and seldom those with severe kidney involvement. The levels do not correlate with disease activity. 25-40% of Patients with subacute cutaneous lupus are Ro and La positive though Ro alone can also be characteristic.
Anti-La antibodies are found, usually together with anti-Ro antibodies in most mothers of babies with complete congenital heart block although a minority of babies born to mothers with La and autoimmune diseases will develop heart block.
|Sample:||Serum Separator Tube (SST)|
|Assay details:||Fluorescence enzyme linked immunoassay (Phadia Immunocap 250): Human recombinant La protein IgG antibodies.|
|Restrictions:||Test is only carried out when ENA screen is positive.|
|Reference range:||Results reported as negative, equivocal or positive.|
|Assay range notes:|
|Turnaround time:||5 – 7 days|
|Analysing laboratory:||Immunology The James Cook University Hospital|