The fluorescent antinuclear antibody test (FANA) utilizes the indirect fluorescent
antibody technique. Antinuclear antibodies in a patient's serum will bind with
nuclear antigens of a tissue cell culture substrate affixed to a slide. Fluorescein-
conjugated antihuman globulin interacts with nuclear antibodies attached to the
cell nuclei in a positive assay which is indicated by an apple-green fluorescence.
If the results for the FANA are negative, the fluorescent intensity of the cells' nuclei
is about the same as that of the negative control, and there is no discernible
pattern in the nucleus.
If the results are positive, the fluorescent intensity of the cells' nuclei is greater
than the negative control, and there is a clearly discernible pattern in the nucleus.
Report positive controls and patients by the specific fluorescent pattern observed.
For a homogeneous pattern, there is smooth, even staining of the nucleus. The
antibodies indicated are anti-native-DNA and anti-DNP. The condition indicated
by a high titer is SLE. The condition indicated by a low titer is RA.
For a peripheral pattern, there is staining of the nuclear membrane only. The
antibody indicated is anti-native-DNA. The condition indicated is SLE.
For a speckled pattern, there is grainy staining throughout the nucleus usually not
affecting the nucleoli. The antibodies indicated are anti-Sm and anti-RNP. Four
possible conditions indicated are SLE, PSS, SS, and MCTD.
For a nucleolar pattern, there is solid staining of the nucleoli. The antibodies
indicated are antinucleolar. The condition indicated is PSS.
The FANA is a laboratory diagnostic aid and by itself is not diagnostic. Positive
results require further testing for specific antinuclear antibody identification and
Another limitation of the FANA is that SLE patients undergoing steroid therapy
may have negative test results. Also, many commonly prescribed drugs may
induce positive results.
End of Lesson 6