If the indirect immunofluorescence assay
on HEp-2 cells (HEp-2 IFA) is positive at 1/80, it is recommended that the
serum be titered to a dilution of at least 1/640 and thereafter the report
should indicate if the titer is
- >1/80
– <1/640
- =1/640
- >1/640
A
dilution of 1/640 is suggested as the minimum requirement. Some laboratories do
not dilute beyond 1/640 for logistic and budgetary considerations, while others
who use some automated ANA IFA technologies will obtain digitally calculated
end point titer results.
Additional notes:
Although
it may be true that for some antibodies, higher titers are more indicative of
an autoantibody-associated rheumatic diseases (AARD), there are caveats when
considering only the HEp-2 IFA method:
- It is not true for the full spectrum of HEp-2 IFA (ANA) patterns
described by ICAP. The most obvious example is the nuclear dense fine speckled
pattern (AC-2 pattern) that has been shown to occur at high titer in the
general population (1), but uncontrolled experience suggest the same is true for
Golgi, centrosome, and some other cytoplasmic patterns.
- A
point in time ANA is not really that revealing on its own. What is more
important to know is whether titers are decreasing, increasing or staying the
same over time.
Reference:
- Mariz HA, Sato EI, Barbosa SH, Rodrigues SH, Dellavance A, Andrade LE. Pattern on the antinuclear antibody-HEp-2 test is a critical parameter for discriminating antinuclear antibody-positive healthy individuals and patients with autoimmune rheumatic diseases. Arthritis Rheum. 2011;63:191-200.