Biomedical text tagging systems are plagued by the dearth of labeled training
data. There have been recent attempts at using pre-trained encoders to deal
with this issue. Pre-trained encoder provides representation of the input text
which is then fed to task-specific layers for classification. The entire
network is fine-tuned on the labeled data from the target task. Unfortunately,
a low-resource biomedical task often has too few labeled instances for
satisfactory fine-tuning. Also, if the label space is large, it contains few or
no labeled instances for majority of the labels. Most biomedical tagging
systems treat labels as indexes, ignoring the fact that these labels are often
concepts expressed in natural language e.g. `Appearance of lesion on brain
imaging'. To address these issues, we propose constructing extra labeled
instances using label-text (i.e. label's name) as input for the corresponding
label-index (i.e. label's index). In fact, we propose a number of strategies
for manufacturing multiple artificial labeled instances from a single label.
The network is then fine-tuned on a combination of real and these newly
constructed artificial labeled instances. We evaluate the proposed approach on
an important low-resource biomedical task called \textit{PICO annotation},
which requires tagging raw text describing clinical trials with labels
corresponding to different aspects of the trial i.e. PICO (Population,
Intervention/Control, Outcome) characteristics of the trial. Our empirical
results show that the proposed method achieves a new state-of-the-art
performance for PICO annotation with very significant improvements over
competitive baselines.

本研究提出了一种方法解决生物医学标记系统中标记实例匮乏的问题，该方法使用预训练编码器为任务提供文本表示，并通过使用标签文本作为输入来制造多个人工标记实例。实验结果表明，这种方法在 PICO 注释任务上实现了最新的最佳性能。