Improving the Phenotyping in chronic pain conditions using real-time pain-reports and additional patient-reported data.

• Applicant: Dr. Alexander Obbarius
• Subject Area: Clinical Psychiatry, Psychotherapy, Child and Adolescent Psychiatry ; Personality Psychology, Clinical and Medical Psychology, Methodology
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 410208849

Persistent pain is a serious therapeutic challenge and a public health epidemic. Although a wide range of treatments are available there is still a substantial number of non-responders. One reason for this is insufficient knowledge about subgroups of chronic pain patients who respond differently to treatment. To address this issue, during the first part of the research fellowship, summary measures of ecological momentary assessment (EMA) data (“Pain indices”) were used as input to latent class analysis to identify subgroups in data from two large trials in fibromyalgia patients (Ntotal>2000). Contrary to expectations, the best latent class model was based on a very small number of pain indices. Three subgroups were identified, which were considerably different in their treatment trajectories. Within the smallest group (about 5%) patients were found to be above-average placebo responders (i.e., the improvement during treatment was greater than in the other placebo groups and in all active treatment groups). These results are promising as they touch on another very important topic in pain research. If patients in this group had been excluded from the clinical trials, the distinction between placebo and intervention group (assay sensitivity) would have been dramatically improved. In order to make these findings applicable in practice, the first aim of the project is to obtain suitable data from clinical pain studies and to replicate previous results with the new data. Furthermore, to find out more about the reasons for the different trajectories, subgroups in the previous study and replication study will be further evaluated using available data such as information about use of rescue medication or side effects. In the second part of the planned project, further aspects of assay sensitivity will be investigated in more detail. The question will be raised as to whether assay sensitivity can be improved by increasing the reliability and/or precision of outcome instruments. Although the possible influence of instrument quality on assay sensitivity has been increasingly discussed in recent years, surprisingly little has been published on this topic. Improving the reliability of instruments could help to improve the ability of instruments to detect "real" changes in symptoms (i.e. in this case pain). In summary, this project could expand the current evidence on phenotypes in chronic pain patients and on assay sensitivity in pain trials and thus improve the treatment of patients with chronic pain.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Arthur Stone, Ph.D.