The term "nuclear speckled" is an overarching competent- HEp-2 IFA pattern that includes both fine speckled (AC-4) and large/coarse speckled (AC-5). In some cases, it can be difficult to define precisely the speckled pattern a sample produces, being either the fine or large/coarse speckled pattern. Obviously, one may use the ICAP competent level terminology AC-4/5. In such case, one may combine the antibody targets and clinical relevance of the individual patterns, i.e., AC-4 and AC-5. Using the competent level AC-4/5 term may also be appropriate in mixed patterns caused by more than one autoantibody specificity in the sample.
Ideally, one should provide the most complete definition of the pattern (expert level), because these provide more specific information on antigenic associations and clinical relevance. For example, as indicated in the "antigen association section" of ICAP website, the nuclear coarse speckled pattern (AC-5) is associated mainly with anti-Sm and anti-U1-RNP antibodies, whereas the nuclear fine speckled pattern (AC-4) has a broader target antigen association. In the ICAP Note #2, AC-4 can be further divided into fine speckled with myriad discrete tiny dots (AC-4a), or simple fine speckled (AC-4b). These are defined patterns and have respective antibody targets, immunological associations, and clinical relevance. The nuclear dense fine speckled pattern (AC-2), on the other hand, should be distinguished from the nuclear speckled patterns AC-4 and AC-5 based on the positive staining of the metaphase plate. With exception of the centromeric pattern (AC-3), the clinical relevance of all patterns is only indicated if the antibody target has been identified.

This is an interesting question and reflects a challenge frequently encountered by ANA laboratories. At the present time, the “pseudo-DFS” nomenclature has not been endorsed by ICAP or included in the ICAP algorithm. Nevertheless, there is published evidence that not all sera having a nuclear “dense” fine speckled pattern with similarly stained mitotic chromatin contain detectable anti-DFS70 autoantibodies. This situation may reflect a HEp-2 IFA pattern that is distinct from the anti-DFS70 positive AC-2 pattern even though it stains the interphase nuclei and mitotic chromatin with a speckled texture. However, the speckled texture is slightly different from the genuine AC-2 pattern (1, 2). The anti-DFS70-positive AC-2 pattern has a speckled texture that is heterogeneous within each nucleus, with some denser speckled areas adjacent to sparser areas; and areas with larger and brighter speckles intercalated with areas with smaller and dimer speckles. The same applies to the staining of mitotic chromatin. Some investigators have suggested the term “pseudo-DFS” to designate sera that do not have these precise AC-2 staining characteristics (1, 2), The Autoantibody Standardizing Committee offers free of charge reference sera with several HEp-2 IFA patterns and antibody specificities (http://www.autoab.org/), including a reference material for AC-2 pattern (with reactivity to DFS70) (3). This can help in the exact recognition of the AC-2 pattern. Note that the specific autoantibody target(s) and the clinical relevance for the pseudo-DFS pattern but anti-DFS70 negative remains to be published.

1. Mahler M, Andrade LE, Casiano CA, Malyavantham K, Fritzler MJ. Anti-DFS70 antibodies: an update on our current understanding and their clinical usefulness. Expert Rev Clin Immunol. 2019;15:241-250.
2. Infantino M, Bizzaro N, Grossi V, Manfredi M. The long-awaited 'pseudo-DFS pattern'. Expert Rev Clin Immunol. 2019 15(5):445.
3. Dellavance A, Baldo DC, Zheng B, Mora RA, Fritzler MJ, Hiepe F, Ronnelid J, Satoh M, Garcia-De La Torre I, Wener MH, Chan EKL, Andrade LEC. 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.