Enhancing User Message Intent Detection in a Mobile Health Smoking Cessation Intervention: Fine-tuning a Large Language Model with Data Downsampling and Error Correction (Preprint)

BACKGROUND Although smoking cessation aids including support groups and nicotine replacement therapy (NRT) can help people quit smoking, quit rates remain low. Emerging mobile health interventions like online support groups can help overcome barriers related to aid accessibility and convenience. Combined with NRT, online support groups hold significant potential but demand continuous, labor-intensive efforts to deliver timely responses that maintain participant engagement. Accurate user intent detection, which is the process of understanding the purpose behind a user’s message, can play a critical role by identifying individual needs and consequently providing timely and proper responses. Recent large language model advancements in natural language processing and artificial intelligence (AI) have shown promise. However, these systems often struggle when faced with a large number of intent categories or the complex nature of human language. Uneven data across intent categories—some rare and others dominant—makes it harder for the system to correctly recognize user intent and respond. OBJECTIVE The main goal of this study was to develop an AI tool, especially a large language model that could accurately recognize users’ message intents, despite imbalances and complexities in data. In our application, users’ message intents were related to a smoking-cessation support-group intervention and utilization of the free nicotine replacement therapy (NRT) provided as part of that intervention. METHODS We consistently used a state-of-the-art public domain large language model, Llama-3 8B from Meta. First, we used the model off-the-shelf. Second, we fine-tuned it on our annotated domain dataset of 25 intent categories. Third, we downsampled the predominant intent category to reduce bias and fine-tuned the model. Finally, we combined downsampling with corrected annotations to create a cleaned dataset for another round of fine-tuning. This stepwise approach progressively improved classification accuracy by addressing prior limitations. RESULTS Without fine-tuning, the large language model achieved an unweighted-average F1-score of 0.29 and a weighted-average F1-score of 0.37, where unweighted treated all categories equally, while weighted emphasized larger ones. Fine-tuning alone achieved unweighted and weighted-average F1-scores of 0.72 and 0.86 respectively. Downsampling plus fine-tuning achieved unweighted and weighted-average F1-scores of 0.80 and 0.85 respectively. Downsampling, fine-tuning and human error correction achieved an unweighted-average F1-score of 86% and a weighted-average F1-score of 90%. CONCLUSIONS On smoking cessation data, large language models performed poorly without fine-tuning, underscoring the need for domain-specific training. However, with domain-specific fine-tuning, performance has suffered because of the highly imbalanced dataset. Downsampling the majority category before fine-tuning improved results moderately, however left room for further enhancement and raised concerns about potential noise in the dataset. Carefully reviewing the misclassified samples has helped identify annotation inconsistencies, and after correcting these errors and fine-tuning the model on the corrected dataset, best performance has been achieved.