History of ANA Testing

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History of ANA Testing

Slide-based ANA testing using a cell substrate started in the 1950s and continues to be the gold standard method. In the early days of ANA testing, rodent tissue (stomach, liver and/or kidney) was commonly used as the substrate. Rodent tissue however had several drawbacks such as small cell size, a lack of dividing cells (mitotics) and poor antigen expression that made interpretation of ANA patterns difficult. In the 1980s, cultured cell lines were examined for utility as an ANA substrate and the human epithelial- like cell line HEp-2 gained popularity. HEp-2's advantages over rodent tissue are:

  • A large nucleus
  • Better antigen expression
  • Abundant mitotic cells that assist in interpretation of the ANA pattern (if grown properly).

More recently a cell line called HEp-2000® has become popular for ANA detection. HEp-2000® is a HEp-2 cell line that has been transfected with the cDNA for overexpression of the SSA/Ro antigen. This results in a substrate with all of the original advantages of HEp-2 plus an added advantage of increased sensitivity for detection of antibodies directed to the SSA/Ro antigen and the ability to identify these clinically significant antibodies during the screening process.(Ref4)

It has also been demonstrated that antibodies to SSA/Ro develop early in the disease process.(Ref5) Perhaps most importantly, if a woman has anti-SSA/Ro antibodies and becomes pregnant there is a risk of the antibodies crossing the placenta, resulting in the fetus developing neonatal lupus and congenital heart block in utero.

The advantage of using these transfected cells is documented in the current Clinical and Laboratory Standards Institute (CLSI) guidelines for ANA testing. Here they note the "dramatically increased" sensitivity of transfected cells for the detection of SS-A/Ro and the unaltered effect of transfection on other ANA patterns.(Ref6)