This study aims to discover, verify and evaluate the potential biomarkers with regard to the diagnosis, prognostic and/or prediction of diabetic chronic wounds.

Investigators will conduct a multicenter prospective case control study consisting of three stages.

In the first stage, investigators will collect clinical data and blood, urine and stool samples from diabetic patients with chronic wound (CWD), diabetic patient without newly identified wound (NWD) and patients without diabetes (ND to discover the candidate bioindicator with differences through combined high-throughput non targeted detection.

In the second stage, investigators will expand the sample size and collect the clinical data and biological samples (blood, urine and stool) of the CWD,NWD and ND participants to verify the difference of the candidate bioindicator in the first stage by targeted technologies.

In the third stage, investigators will collect the clinical data and biological samples (blood, urine and stool) of the CWD and NWD participants to evaluate the value of these candidate bioindicators as biomarkers.

Inclusion Criteria:

1. Age between 18 and 75;
2. Signed the informed consent form；
3. Subjects in the ND group are the healthy participants without diabetes；
4. Subjects in the NWD group are the diabetic participants without newly identified wounds；
5. Subjects in the CWD group are the diabetic participants with chronic wounds

Exclusion Criteria:

1. With sever acute underlying diseases of the brain, heart, lungs, liver and/or kidney;
2. No diabetes but combined with lower limb arterial stenosis, occlusion or other conditions affecting wound healing or other causes of wounds such as varicose veins in the lower limbs;
3. Special exclusion criteria for blood, urine and stool samples taking.

Participants are required to complete a structured questionnaire for assessment of inclusion requirement and then divided into the CWD group, NWD group and the ND group.