The purpose of this study is to analyze associations between symptoms and specific markers in the blood in patients suffering from neuropathic pain linked to diseases of different origin. Such markers could be utilized in the future for precise diagnosis of neuropathic pain and might lead to targeted pain treatment.

On average, 3-8% of the German population suffers from neuropathic pain, which can occur after damage of somatosensory nerves in the peripheral or central nervous system. In terms of a "personalized" medicine, only a strict separation of neuropathic and chronic pain allows an individualized therapy to reduce pain severity and to enhance patients' quality of life.

Currently, the diagnosis of neuropathic pain is based on the medical history, the subjective description of somatosensory symptoms and the application of (non-genetic) diagnostic tests. To improve diagnosis and therapy of complex disorders for individual patients, novel methods are introduced based on flow cytometric (FACS) analysis of human immune cells or analysis of the human genome (genomics). Those techniques can support the identification of characteristic features indicating ongoing individual pathophysiologic processes in the body (biomarkers).

Often diseases are based on a complex relationship between genetics, environmental factors and the manifestation of the disease. To capture this complexity via genomics, phenotypical and genotypical data of high quality and detailed information about the study population are required.

This observational study includes patients suffering from painful and non-painful neuropathies associated with HIV-infection, diabetes mellitus and breast cancer. With the targeted application of validated questionnaires (such as the Brief Pain Inventory, Pain Catastrophizing Scale, Hospital Anxiety and Depression Scale, Ten-Item Personality Inventory, 36-Item Short Form Health Survey, and the Insomnia Severity Index) and parallel usage of genomics or FACS analysis of selected biomarkers in the blood, this study will provide information about the manifestation of certain genes or immune markers which are directly correlated to the symptoms of the disease. Additional performance of neuropsychological/cognitive tests and quantitative sensory testing (QST) will enhance the phenotypic profile. Identification of potential indicators could be utilized prospectively to precisely diagnose and effectively treat neuropathic pain.

Inclusion Criteria:

• HIV-associated neuropathy
• Sufficient knowledge of the German language

Exclusion Criteria:

• Co-incident severe central nervous system diseases
• Major psychiatric conditions
• Dementia
• Limited mental capacity or limited German language skills
• Intoxication with alcohol or recreational drugs within the last 48 hours of the study

Hospitals, primary care clinics, resident physicians