Perneger et al. excluded patients "too sick to complete a questionnaire" from a mail survey.
Sheikh
Kazim
K
D019538:Health Care Surveys / Q000379:methods*; D006801:Humans; D007297:Inpatients / Q000523:psychology*; D017060:Patient Satisfaction / Q000706:statistics & numerical data*; D018579:Patient Selection; D015983:Selection Bias; D012803:Sick Role; D011795:Surveys and Questionnaires