Guest Claire M, Harris Rob, Anjum Iqbal, Concha Astrid R, Rooney Nicola J
Medical Detection Dogs, Greenway Business Park, Milton Keynes, United Kingdom.
US Army Research Office - Texas Tech University, Lackland, TX, United States.
Front Vet Sci. 2020 Aug 18;7:525. doi: 10.3389/fvets.2020.00525. eCollection 2020.
Training new medical odors presents challenges in procuring sufficient target samples, and suitably matched controls. Organizations are often forced to choose between using fewer samples and risking dogs learning individuals or using differently sourced samples. Even when aiming to standardize all aspects of collection, processing, storage and presentation, this risks there being subtle differences which dogs use to discriminate, leading to artificially high performance, not replicable when novel samples are presented. We describe lessons learnt during early training of dogs to detect prostate cancer from urine. Initially, six dogs were trained to discriminate between hospital-sourced target and externally-sourced controls believed to be processed and stored the same way. Dogs performed well: mean sensitivity 93.5% (92.2-94.5) and specificity 87.9% (78.2-91.9). When training progressed to include hospital-sourced controls, dogs greatly decreased in specificity 67.3% (43.2-83.3). Alerted to a potential issue, we carried out a methodical, investigation. We presented new strategically chosen samples to the dogs and conducted a logistic regression analysis to ascertain which factor most affected specificity. We discovered the two sets of samples varied in a critical aspect, hospital-processed samples were tested by dipping the urinalysis stick into the sample, whilst for externally sourced samples a small amount of urine was poured onto the stick. Dogs had learnt to distinguish target aided by the odor of this stick. This highlights the importance of considering every aspect of sample processing even when using urine, often believed to be less susceptible to contamination than media like breath.
训练新的医学气味在获取足够的目标样本和匹配得当的对照样本方面存在挑战。各机构常常被迫在使用较少样本并冒着让狗识别个体的风险，与使用来源不同的样本之间做出选择。即使旨在使采集、处理、储存和呈现的所有方面标准化，这也存在细微差异的风险，而狗会利用这些差异进行区分，从而导致人为的高性能，在呈现新样本时无法复制。我们描述了在早期训练狗从尿液中检测前列腺癌的过程中吸取的教训。最初，六只狗接受训练，以区分医院来源的目标样本和据信以相同方式处理和储存的外部来源对照样本。狗的表现良好：平均敏感度为93.5%（92.2 - 94.5），特异度为87.9%（78.2 - 91.9）。当训练进展到纳入医院来源的对照样本时，狗的特异度大幅下降至67.3%（43.2 - 83.3）。意识到一个潜在问题后，我们进行了系统的调查。我们向狗展示了新的经过策略性选择的样本，并进行了逻辑回归分析，以确定哪个因素对特异度影响最大。我们发现两组样本在一个关键方面存在差异，医院处理的样本是通过将尿液分析试纸浸入样本中进行检测的，而对于外部来源的样本，则是将少量尿液倒在试纸上。狗已经学会借助试纸的气味来区分目标。这凸显了即使使用通常被认为比呼吸等介质更不易受污染的尿液时，考虑样本处理各个方面的重要性。
