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Table 3 Stepwise approach to main scale item removal using exploratory factor analysis and Cronbach’s alpha

From: Testing the psychometric properties of the illness perceptions questionnaire for OCD (IPQ-O)

Question number Item Justification for removal
76 items IPQ-O
 OIP70 My OCD is likely to be permanent rather than temporary Inspection of correlation matrix showed this item highly correlated (.825) with OIP67. OIP67 retained due to lower missing data.
75 items IPQ-O
 OIP14 My symptoms get worse when my daily routine needs to changea No factor loadings above .3
 OIP13 My symptoms are worse when I am in particular placesa No factor loadings above .3
 OIP2 I find it hard to separate what is ‘me’ and what is my OCDa No factor loadings above .3
 OIP35 My OCD gets worse when I have more timea No factor loadings above .3
 OIP22 My OCD makes me obsessive about things in general, such as my hobbies and interestsa No factor loadings above .3
70 item IPQ-O
 OIP9 My symptoms of OCD are affected by my physical healtha No factor loadings above .3
 OIP24 My OCD makes me feel guiltya No factor loadings above .3
68 item IPQ-O
  Factor 1: OIP48 – Other people’s behaviour can make my OCD worsea Item reduction of consequences scale - α reduced .001 when removed.
  Factor 1: OIP10. My OCD gets worse when I need to conceal my symptomsa Item reduction of consequences scale - α reduced .001 when removed.
  Factor 5: OIP26. Hearing or talking about OCD could lead to me picking up new symptomsa No change in α if removed.
Final 65 items
  1. Items marked awere new items, not included in the original IPQ-R