. 2019 Jul 10;19:217. doi: 10.1186/s12888-019-2195-3

Table 3.

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

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 change^a	No factor loadings above .3
OIP13	My symptoms are worse when I am in particular places^a	No factor loadings above .3
OIP2	I find it hard to separate what is ‘me’ and what is my OCD^a	No factor loadings above .3
OIP35	My OCD gets worse when I have more time^a	No factor loadings above .3
OIP22	My OCD makes me obsessive about things in general, such as my hobbies and interests^a	No factor loadings above .3
70 item IPQ-O
OIP9	My symptoms of OCD are affected by my physical health^a	No factor loadings above .3
OIP24	My OCD makes me feel guilty^a	No factor loadings above .3
68 item IPQ-O
	Factor 1: OIP48 – Other people’s behaviour can make my OCD worse^a	Item reduction of consequences scale - α reduced .001 when removed.
	Factor 1: OIP10. My OCD gets worse when I need to conceal my symptoms^a	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 symptoms^a	No change in α if removed.
Final 65 items

Items marked ^awere new items, not included in the original IPQ-R