Chronic obstructive pulmonary disease (COPD) is a disease of the lungs that makes it hard to breathe. COPD can lead chronic breathing problems and even death. COPD is very common, and it is expected that by the year 2020 it will be the third highest cause of death in the world. One of the main causes of this devastating disease is smoking cigarettes, but the start of COPD can also be triggered by other environmental factors, such as allergens. COPD is a complex disease. There is no cure for COPD, but symptoms (difficulty breathing) can be managed with treatment. Inhaled corticosteriods are commonly used, but not effective in all patients. One factor that may be useful in helping decide which patients may respond to inhaled corticosteroids are "eosinophils" - a type of white blood cell. An eosinophil count is a blood test that measures the quantity of eosinophils in a patient's body. Patients with larger numbers of these white blood cells (eosinophils) may respond better to inhaled corticosteroid treatments. This would avoid unnecessary use of corticosteroids in patients unlikely to see improvement in breathing difficulties. But it is first important to know how stable eosinophil counts are in patients with COPD. The study aims to see how stable eosinophil counts are in COPD patients and non-COPD patients. We will also look at stability by eosinophil counts at baseline gender, age, and smoking status.
Rationale: Chronic Obstructive disease is an inflammatory disease which is known to affect the airways of the lungs. Pathophysiology of the disease is mediated by release of macrophages, eosinophils, neutrophils , cytokine, and CD8+ lymphocytes. Peripheral eosinophil counts are increasingly recognised as a biomarker for response to inhaled corticosteroids in COPD and may assist in better targeting treatments to patients who will benefit most. However, little is known about the long-term stability of blood eosinophils in COPD and the impact of age, gender and eosinophil counts. Greater understanding of this subject area can help gain better understanding needed to tailor COPD treatments to specific patient groups, potentially reducing the cost of managing the disease and increasing the chance of improved outcomes.
Objective: The study therefore aims to determine the stability of blood eosinophil counts in COPD patients and non-COPD patients.
Methods: The primary outcome will be the stability of blood eosinophil count, with stability defined as a count remaining persistently at <2% or >/= 2%. Patients will be followed until end of study period, or when defined as unstable ("failure"). Kaplan Meier curves will be plotted to show eosinophil stability, stratified by eosinophil counts at baseline age groups, gender, and smoking status.
Health Outcomes to be Measured:
Stability of blood eosinophil count