Pain is a subjective feeling,and pain experts have been trying to assess it using objective methods. Pain index (PI) is extracted from electroencephalographic as an objective diagnostic tool for chronic pain. This study is a diagnostic test aims to explore the reliability and validity of PI, with numerical rating scale(NRS) as the gold standard.

Chronic pain outpatients between 18 and 80 years old, NRS ≥4 at first visit and receive injection or shockwave therapy will be included. After informed consents signed, the age, gender, dominant hand and hospital anxiety and depression scale (HADS) will be collected. Each patient will be connected with a multifunctional monitor HXD-1 for 8 minutes to access EEG in a quiet environment before pain treatment and 30 minutes after pain treatment. NRS will also be recorded before pain treatment and 30 minutes after pain treatment. PI will be extracted from EEG by analysts.

In order to reduce environmental effects, the same quiet research environment will be used throughout the study. All data will be obtained and recorded by the same person, and all PI will be analyzed and calculated by the same person.

SPSS 20.0 will be used to analyze the data, Pearson's correlations and Kappa consistency test to analyze the validity and reliability of PI. The receiver operating characteristic curve will be use to analyze the sensitivity and specificity of PI to evaluating moderate and severe pain(NRS≥4). A multiple linear regression equation with PI as dependent variable and anxiety score and depression score as independent variables will be used to evaluate the influence of anxiety and depression on PI.

Inclusion Criteria:

• 1.chronic pain patients diagnosed lumbar disc herniation, osteoarthritis or other chronic pain diseases, who will received injection therapy or shockwave therapy at clinic.
• 2.patients age 18-80 years-old
• 3.patients with an NRS pain score ≥ 4,
• 4.patients who voluntarily participate in the test and sign the informed consent forms.

Exclusion Criteria:

• 1.patients with central nervous system disorders, such as epilepsy, cerebral infarction, or cerebral hemorrhage,
• 2.patients with mental disorders,
• 3.patients with a history of long-term use of psychotropic drugs.
• 4.patients who can't understand NRS.

The sample capacity calculation is based on the sensitivity/specificity of the diagnostic test allowed a minimum sensitivity of 80%, a minimum specificity of 80%, a significance level α of 0.01, an allowable error of 0.1 strictly.The estimated sample is 107 patients. Considering a predicted shedding rate of 10%, 118 patients will be enrolled.