Targeting therapy in people with severe asthma: A retrospective cohort study describing commonly measured biomarkers (eosinophil count and IgE levels) in patients with severe asthma

Study type

• Study topic:
  Disease /health condition
• Study type:
  Non-interventional study
• Scope of the study:
  Disease epidemiology
• Data collection methods:
  Secondary use of data

Non-interventional study

• Non-interventional study design:
  Cohort

Study drug and medical condition

• Medical condition to be studied:
  Asthma

Population studied

• Short description of the study population:
  All patients currently on the NHSGGC database who had read or ICD coded diagnosis for asthma ever recorded, age ≥ 18 years two years prior to the index date, ≥ 1 prescription for any of SABA, ICS, ICS/LABA combination in the two years prior to the index date, ≥ 1 estimation of IgE in the two years prior to the index date.
• Age groups:
  • Adults (18 to < 46 years)
  • Adults (46 to < 65 years)
  • Adults (65 to < 75 years)
  • Adults (75 to < 85 years)
  • Adults (85 years and over)
• Special population of interest:
  Other
• Special population of interest, other:
  Asthma patients
• Estimated number of subjects:
  2000

Study design details

• Main study objective:
  To categorise people with severe asthma according to their eosinophil and total IgE biomarker status.
• Outcomes:
  Description and correlation coefficient of maximum EOS versus maximum IgE among those with asthma and receiving therapy at British Thoracic Society step 4 level and above, Number with same day biomarker measurementMaximum IgE in past 2 years Maximum EOS in past 2 years Same day EOS versus same day IgE. Maximum EOS by compliance with inhaled steroid medication Characteristics of patients at BTS step 4 and above by EOS/IgE combination group Number fulfilling the criteria for Xolair and the possible criteria for reslizumab Truncated
• Data analysis plan:
  Creation of new IgE and EOS variables− Maximum IgE in past two years − An IgE >75 and ≤1500 at any time in past two years − The number of measurements of IgE levels in past two years − The value of IgE corresponding to the same day measurement as EOS at any time in past two years − Maximum EOS in past two years − An EOS ≥400 at any time in the past two years − The number of measurements and the proportion of EOS levels ≥400 in the past two years − The value of EOS corresponding to the same day measurement as IgE at any time in the past two years Frequency plots to illustrate the distribution of the continuous variables. Scatterplots to assess the relationship between two continuous variables such as IgE and EOS. Correlation coefficients to assess the linear relationship between two continuous variables such as IgE and EOS (Spearmans correlation will be used if both variables are skewed and Pearson correlation if one or both variables are normally distributed).