Limites e desafios na caracterização e interpretação dos padrões nucleares AC-4 (A e B), AC-5 e BAC-4.

Abstract

The indirect immunofluorescence (IIF) technique is widely used for detecting autoantibodies in human serum. It is characterized by its high sensitivity, enabling the estimation of autoantibody concentration through fluorescence intensity and the identification of patterns with clinical relevance. Recommended by the American College of Rheumatology, IIF tests are employed in the investigation of autoimmune diseases, with specific guidelines for their performance and interpretation provided by the Brazilian Consensus on Autoantibodies (CBA) and the International Consensus on ANA Patterns (ICAP). Although test positivity can occur in individuals without clinical manifestations, its request must be based on appropriate clinical reasoning. Furthermore, other technical and clinical aspects must be considered to avoid misinterpretation. In 2021, the ICAP advanced the subclassification of the fine speckled nuclear pattern (AC-4), dividing it into subgroups AC-4a and AC-4b, which were subsequently incorporated into the Brazilian consensus in 2022. In the laboratory setting, distinguishing AC-4 from AC-5 and BAC-4 patterns has long been challenging, given their relative prevalence and potential association with significant clinical conditions. In this context, the present study, through a narrative review focusing on publications addressing the above-mentioned cellular patterns and their variations, aimed to review the morphological characteristics of speckled patterns with negative staining, their clinical relevance, and their immunological identities. The goal is to provide support for more accurate analyses by clinical laboratories and more informed interpretation of these findings by attending physicians.