Detection identification and clinical significance of ANAs

ANAs with I FT

The IFT is generally used as a screening assay for the presence of ANAs. The method is highly sensitive and detects almost all ANA specificities. Most laboratories now use cultured cells as substrate instead of tissue sections. Sera from patients with generalized autoimmune diseases mostly have several distinct ANAs at the same time. Since the titers of these antibodies differ, titration of the serum can reveal the strongest ANAs giving a certain pattern of nuclear fluorescence. Homogeneous patterns are frequently observed in patients with SLE or rheumatoid arthritis (RA), speckled or granular patterns in sera from patients with Sjogren's syndrome or scleroderma. Nucleolar fluorescence is often seen in patients with progressive systemic sclerosis (PSS). These associations, however, are of limited value to the clinician.

Only the discrete speckled pattern of nuclear fluorescence is informative, since this points to the presence of antibodies to centromeres. This should be confirmed by performance of the IFT on mitotic cells or chromosome spreads. Also the presence of other types of nuclear fluorescence is mostly the start of studies to specify the kind of the ANA.

Nearly all patients with SLE have ANAs, mostly in high titers. In RA, Sjogren's syndrome, PSS, MCTD, myasthenia gravis and chronic active hepatitis the frequency of the ANAs and the titers of these antibodies are considerably lower (Table 3).

A negative result in the IFT does not necessarily mean that ANAs are not present. It is known that low titered reactivities to Ro/SS-A, rRNP and Jo-1 are relatively difficult to detect in this assay.

Most laboratories have tested sufficient sera from healthy individuals to be aware of the statistical limits between normal and pathological ANA titers. Nevertheless, it should be noted that not only generalized autoimmune diseases show a preponderance for women and adults, but that also healthy elderly women have a far greater tendency to show these antibodies than young boys. A positive ANA in a boy, therefore, draws more attention than the same ANA in a woman over 60 years of age.

LE cell test

In 1948 Hargraves described for the first time the occurrence of LE cells. The demonstration of these cells was a great help to define the complicated clinical picture of SLE (Table 3). Later on, the 'LE cell factors' were identified as autoantibodies and the 'LE cells' as granulocytes which had phagocytosed complexes of these autoantibodies and nuclei of other cells. Nucleosomes are able to inhibit the formation of 'LE cells', in contrast to free dsDNA or histones. Thus, it appears that the LE cell phenomenon is related to the presence of antinucleosome autoantibodies. After 45 years the test is still in use but with the introduction of more specific methods, it has become somewhat redundant.

Anti-DNA

Antibodies to DNA can be found in the circulation of the majority of patients with SLE. They are quite specific for this disease, which makes their detection an important diagnostic aid to the clinician (Tabic 3). Fluctuations in the level of anti-dsDNA in an individual patient generally parallel the clinical status of that patient. Under defined conditions, increases in the level of anti-DNA predict an upcoming flare of the disease. Indeed, it has recently been shown that instalment of (prednisone) treatment on the basis of increasing levels of anti-DNA may prevent the exacerbation from becoming overt. Furthermore, the presence of anti-dsDNA may precede the diagnosis of SLE by more than a year.

Table 3 Frequencies of ANA in various autoimmune diseases (percentages in round figures) ANA Autoimmune disease
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