Historically measurement of antinuclear antibodies (ANA) was done by indirect immunofluorescence using serial dilutions of patient serum. ELISA testing offers many advantages and is becoming more widely used. A clinician may need to evaluate a patient with results from both types of testing, both of which differ in their units of reporting.
NOTE: The 2 tests use different units since the tests use different methodologies. Although one result will not map directly to another an approximation is usually sufficient.
Intensity Grade
Dilution
negative
<= 1:20
+/-
1:40 or 1:80
1+
1:160 to 1:320
2+
1:640
3+
1:1,280
4+
1:2,560
Intensity Grade
ELISA Units
negative
< 1.0
weakly positive
1.0 - 2.9
positive
3.0 - 5.9
strongly positive
>= 6.0
Dilution
ELISA Units
<= 1:20
< 1.0
1:40 or 1:80
1.0 - 2.9
1:160 to 1:640
3.0 - 5.9
1:1,280 to 1:2,560
>= 6.0
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