Laboratory of Neuropsychophysiology, Faculty of Psychology and Education Sciences, University of Porto, Porto, Portugal.
Brain and Pain (BaP) Research Group, IniPain Lab, Department of Clinical Psychology and Psychobiology, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Pain. 2019 Dec;160(12):2679-2690. doi: 10.1097/j.pain.0000000000001664.
Conditioned pain modulation (CPM) is a promising psychophysical biomarker of central pain mechanisms because it significantly discriminates patients with chronic pain from healthy controls. Nevertheless, it is unclear in what extent CPM assessed experimentally is correlated with clinical manifestations of pain. To assess the concurrent validity of CPM, we performed a systematic review of the literature reporting correlations between CPM responses and pain intensity, disability, duration, and area in patients with different chronic pain conditions. We included 32 studies that altogether encompassed data from 1958 patients and provided 62 correlations. The majority of the results (69%) reported nonsignificant correlations between CPM efficiency and clinical manifestations of pain, whereas the remaining results showed a correlation between CPM reduction and worse clinical symptoms of pain. The modality of stimulation, the type of pain, and the stimulation site appear to be critical variables that influenced the pattern of results. Given that most of the studies were conducted with highly heterogeneous methodologies and unclear risk of bias, the findings highlight the need for future studies using standardized measures of clinical and experimental pain before considering CPM as a valid biomarker of pain. We discuss some guidelines to overcome the constraints in this promising line of research.
条件性疼痛调制（CPM）是一种有前途的中枢疼痛机制的心理物理生物标志物，因为它可以显著地区分慢性疼痛患者和健康对照者。然而，CPM 在多大程度上与疼痛的临床症状相关还不清楚。为了评估 CPM 的同时效度，我们对报告 CPM 反应与不同慢性疼痛患者的疼痛强度、残疾、持续时间和面积之间相关性的文献进行了系统评价。我们纳入了 32 项研究，这些研究共包含了 1958 名患者的数据，并提供了 62 个相关性。大多数结果（69%）报告 CPM 效率与疼痛的临床症状之间无显著相关性，而其余结果表明 CPM 减少与疼痛的临床症状恶化之间存在相关性。刺激的方式、疼痛的类型和刺激部位似乎是影响结果模式的关键变量。鉴于大多数研究采用了高度异质的方法学和不明确的偏倚风险，这些发现强调了在将 CPM 视为疼痛有效生物标志物之前，需要使用标准化的临床和实验疼痛测量方法进行未来研究。我们讨论了一些克服这一有前途研究领域限制的指导方针。
