Nuclear Fine Speckled ? Validate Diagnosis Before Sign-Out

The HEp-2 indirect immunofluorescence assay (IFA) remains the most widely used method for detecting autoantibodies associated with systemic autoimmune rheumatic diseases (SARD) and other systemic autoimmune conditions (SAID). This technique enables the screening of a broad range of clinically significant autoantibodies. Importantly, the test provides three key information: whether autoantibodies are present in the sample, the antibody titer and the observed immunofluorescence pattern. Both the titer and the fluorescence pattern play a critical role in distinguishing clinically meaningful positive results from those that may occur in individuals without autoimmune disease. Furthermore, the observed HEp-2 IFA pattern can offer preliminary insight into the likely target autoantigens, helping guide further testing for specific autoantibodies and supporting clinical diagnosis and management.

But here is one twist, among the recognized patterns, the dense fine speckled (DFS) pattern (AC-2) has often been associated with apparently healthy individuals. However, this association is conclusive only when the target antigen is confirmed to be monospecific for DFS70. Current evidence suggests that DFS70 autoantibodies are more commonly linked to non-autoimmune conditions rather than systemic autoimmune diseases.

Prior to the recent new classification of AC-30 as a separate pattern differentiating from AC-2, cases showing AC-2-like features lacking anti-DFS70 antibodies were frequently reported. It is likely that many of these cases would now be more accurately categorized as AC-30. While AC-30 shares morphological similarities with AC-2 both presenting as fine speckled patterns staining interphase nuclei and the metaphase plate, emerging data indicate that these patterns are associated with different immunological profiles.

It is also important to recognize that, in routine laboratory practice, not all samples will exhibit clearly distinguishable pattern characteristics. In such instances, interpretation should remain cautious, taking into account a broader range of possible autoantibody associations and their potential clinical relevance.

References

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2. Mahler M, Parker T, Peebles CL, et al. Anti-DFS70/LEDGF antibodies are more prevalent in healthy individuals compared to patients with systemic autoimmune rheumatic diseases. J Rheumatol. 2012;39(11):2104-2110.

3. Ochs RL, Mahler M, Basu A, et al. The significance of autoantibodies to DFS70/LEDGFp75 in health and disease: integrating basic science with clinical understanding. Clin Exp Med. 2016;16(3):273-293.

4. 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.

5. Dellavance A, Baldo DC, Zheng B, Mora RA, Fritzler MJ, Hiepe F, Ronnelid J, Satoh M, et al. Establishment of an international autoantibody reference standard for human anti-DFS70 antibodies: proof-of-concept study for a novel Megapool strategy by pooling individual specific sera. Clin Chem Lab Med. 2019;57:1754-63.

6. Mahler M, Fritzler MJ. The clinical significance of the dense fine speckled immunofluorescence pattern on HEp-2 cells for the diagnosis of systemic autoimmune diseases. Clin Dev Immunol. 2012;2012:494356.

7. Sanchez-Hernandez ES, Ortiz-Hernandez GL, Ochoa PT, Reeves M, Bizzaro N, Andrade LEC, Mahler M, Casiano CA. The Nuclear Dense Fine Speckled (DFS) Immunofluorescence Pattern: Not All Roads Lead to DFS70/LEDGFp75. Diagnostics (Basel). 2023;13.

8. Durmus MA, Komec S. Frequency of the AC-2 pattern's new variant (AC-30) and detection of different immunological relationships. Clin Immunol. 2025;278:11053.