The goal of this observational study is to improve the epidemiological data of pancreatic exocrine insufficiency in China, determine the FE-1 cut-off value for the classification of PEI, and explore the characteristic differences between T3cDM and type 2 diabetes mellitus in clinical symptoms and laboratory indicators.

Pancreatic exocrine insufficiency (PEI) refers to the reduction in the synthesis and secretion of pancreatic enzymes caused by various reasons, which leads to malabsorption and even nutritional deficiencies. The main causes of PEI include chronic pancreatitis (CP), acute pancreatitis, pancreatic cancer, pancreatectomy, enterectomy, diabetes mellitus and cystic fibrosis. Due to its numerous etiologies, the current prevalence of PEI is uncertain and very varied. The prevalence of PEI in the Chinese population is still lacking. Diagnosis of PEI in clinical practice is hindered by the lack of accurate tests, and it usually requires the combination of symptoms, nutritional markers and a noninvasive pancreatic function test in the appropriate clinical context. At present, the fecal elastase-1 (FE-1) test is the most widely applied non-invasive approach in routine clinical practice.

First, the study plans to record the baseline data of participants and perform the FE-1 test in specific elderly population and community population, in order to improve the epidemiology of PEI in China.

Second, the study will perform the FE-1 test in 100 CP patients, in order to determine the FE-1 cut-off value for the classification of PEI (mild-moderate and severe), using the coefficient of fat absorption as the "gold standard".

Third, people with CP often have diabetes mellitus which is described as type 3c diabetes mellitus (T3cDM). However, there are no recognized diagnostic criteria for T3cDM. Studies have shown that close to 50% of T3cDM cases are misclassified, most of which are diagnosed as type 2 diabetes mellitus (T2DM). According to certain research, the early stages of T3cDM are characterized by insufficient insulin and C-peptide secretion. The study will provide laboratory testing to 300 patients with T3cDM and T2DM in order to compare the differences and create T3cDM diagnostic criteria.

For elderly population and community population:

Inclusion Criteria:

1. Agree to participate in the study and sign the informed consent.
2. Age of elderly participants are over 60 years old and the participants from community is unlimited.

Exclusion Criteria:

1. Participants in critical condition.
2. Have mental disorders and unable cooperate with investigators.
3. Have received bladder replacement with ileocolon surgery, or have intestinal obstruction and other diseases that can not defecate.

For chronic pancreatitis patients:

Inclusion Criteria:

1. Patients with chronic pancreatitis.
2. Age between 18 and 80 years.

Exclusion Criteria:

1. Pregnant or breastfeeding women
2. Participants in critical condition.
3. Have mental disorders and unable cooperate with investigators.
4. Have received bladder replacement with ileocolon surgery, or have intestinal obstruction and other diseases that can not defecate.
5. Fecal sample quality, storage and transportation do not meet the requirements of fecal elastase-1 test.
6. Have undergone gastrectomy or pancreatectomy more than once.

For chronic pancreatitis patients with diabetes and patients with type 2 diabetes mellitus:

Inclusion Criteria (meet 1 or 2):

1. Patients with chronic pancreatitis and diabetes mellitus.
2. Patients with type 2 diabetes mellitus.

Exclusion Criteria:

1. Patients with type 2 diabetes mellitus.
2. Participants in critical condition.
3. Have mental disorders and unable cooperate with investigators.

Elderly participants will be recruited from several nursing homes. Community participants will be recruited from the community in Shanghai, China. Patients whti chronic pancreatitis and type 2 diabetes mellitus come from Changhai Hospital, Ruijin Hospital and Shanghai General Hospital.