Suggested Rational Considerations for ANA-IF and ENA-Profile Test Requisition: Clinical Manifestation, Gender, Pattern, and Titer of ANA-IF

BACKGROUND: The anti-nuclear antibody
immunofluorescence (ANA-IF) test is used for
screening of autoantibody presence in patients with
suspected autoimmune disease. Positive ANA-IF should be
followed-up with extractable nuclear antigens profile
(ENA-profile). High ANA-IF sensitivity combined with
low ENA-profile sensitivity, and the evolution of ANA-IF
requests may result in a higher number of positive ANAIF
but negative ENA-profile. It is necessary to make an
objective assessment in determining the conditions
in which rational ANA-IF and ENA-profile should be
suggested.
METHODS: Data were retrieved retrospectively from
the medical records of subjects who performed both
ANA-IF and ENA-profile. ANA-IF were examined using
immunofluorescence principle with cut-off 1:100. ENAprofile
which contained sixteen purified antigens was
performed using line-immunoblot principle. Data was
analyzed descriptively and analytically using SPSS, and
significant result was indicated if p<0.05.
RESULTS: The ANA-IF result was dominated by negative
(44.9%) and positive-speckled, titer 1:100 (32.9%). Of 923
subjects with positive ANA-IF, 45.4% had a negative ENAprofile.
Of 751 subjects with negative ANA-IF, 10.2% had
positive ENA-profile. In subjects whose specific clinical
entity, the ANA-IF sensitivity and negative predictive value
(NPV) in detecting ENA-profile were 93.8% and 93.3%,
respectively, but the positive predictive value (PPV) was
63.2%. Women with specific autoimmune manifestation
accompanied by ANA-IF homogeneous ≥1:100, or
centromeres ≥1:100, or speckled ≥1:320 might have been
predicted as subsequent positive ENA-profile with area
under curve (AUC) of 77.2%, 76.9%, 79.2%, respectively.
CONCLUSION: ANA-IF should only be indicated for
those with specific clinical symptoms. For woman with
typical symptoms, the presence of positive ANA-IF with
homogeneous ≥1:100, or centromeres ≥1:100, or speckled
≥1:320 should be further followed-up by ENA-profile