The incidence of thrombocytopenia in ICU patients with severe illness ranged from 8.3% to 67.6%, and ranged from 14% to 44% during ICU treatment.Severe patients with thrombocytopenia also have significantly increased bleeding events and blood transfusions, and even a significantly increased risk of death.This study examines whether elevated platelets benefit patients with pneumonia

Inclusion Criteria:

• Clinical diagnosis of pneumonia (community acquired pneumonia, hospital acquired pneumonia or ventilator associated pneumonia);
• Voluntarily signed informed consent;
• ≥18 years old;
• Platelet count ≤75×109/L

Exclusion Criteria:

• A history of hematopoietic stem cell transplantation or solid organ transplantation such as liver, kidney or lung;
• Hematological malignancy;
• Immune thrombocytopenia, such as SLE, ITP, TTP, etc.
• The length of stay in ICU is less than 24h;
• Pregnant or lactation patients;