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Published on: January 17, 2018
Automated ICAP AC-30/AC-2 discrimination on HEp-2 indirect immunofluorescence: development and clinical validation of
Changmeng Wu1, Kechi Fang2, Chuan Li3
1Department of Laboratory Medicine, Peking University Shenzhen Hospital, Shenzhen 518000, PR China.
Background:
Accurate discrimination between the AC-2 nuclear dense fine speckled pattern and the AC-30 nuclear fine speckled pattern with mitotic plate on HEp-2 indirect immunofluorescence is required for ICAP-compliant reporting but remains technically challenging. The 7th ICAP workshop established AC-30 as a distinct entity. Current automated systems operate at the competent level and do not address this expert-level distinction. In addition, the clinical interpretation of AC-2 depends on the complete autoantibody profile rather than pattern morphology alone, underscoring the need for precise and standardized pattern recognition.
Methods:
We developed a retrieval-based diagnostic software module for second-stage AC-2 and AC-30 discrimination in specimens with confirmed mitotic plate positivity. The module integrates a MaxViT encoder with a Milvus vector database. It was developed on a retrospective cohort of 557 cases and independently validated on a prospective clinical cohort of 103 cases from a tertiary referral center. Performance was compared across six encoder architectures using both softmax classification and similarity-based retrieval.
Results:
The optimal configuration achieved 95.1% overall accuracy on the internal hold-out validation set, with 100% precision and 90.6% recall for AC-30, resulting in no false-positive AC-30 assignments. Similarity-based retrieval consistently improved AC-30 precision across all evaluated architectures and demonstrated enhanced reproducibility across repeated runs. Each prediction was accompanied by a retrieved reference image, providing an interpretable and auditable evidence trail for laboratory quality assurance.
Conclusion:
This study presents a validated retrieval-based diagnostic software module for expert-level AC-2/AC-30 discrimination under updated ICAP nomenclature. The system improves class-specific precision while maintaining reproducibility and interpretability. Its vector database design enables incremental updates without retraining, supporting practical implementation in clinical laboratories as ICAP standards evolve. The module is designed as an assistive tool to support expert interpretation rather than replace clinical decision making.
