Description
The VOCI was designed to provide a self-report assessment of a range of obsessions, compulsions, avoidance behaviour, and personality characteristics of known or theoretical importance in obsessive-compulsive disorder (OCD). It has 55 questions rated on a five point Likert-type scale. It is useful in tracking the underlying cognitive structure of OCD and assessing symptoms over time. This scale is a more up to date revision of the Maudsley Obsessional Compulsive Inventory-Revised (MOCI-R).

Validity
Thordarson et. al. (2004) evaluated the factor structure of the MOCI-R and modified the scale to produce a test with a high level of internal consistently and high loading factors (see reference). The authors established the validity of the VOCI through testing individuals with known diagnoses of either OCD (n = 88), depression or anxiety (n = 60). These scores were compared to community adult group (n = 39) and a student group (n = 200). A comparison between the mean score for the OCD sample and the mean for each comparison groups was conducted, using the Dunnett method of multiple comparisons. The OCD group scored significantly higher than the other groups on the VOCI total score, Contamination, Checking, Just Right, and Indecisiveness subscales. A t-test analysis was also undertaken to see if the scale could discriminate between different subtypes of OCD. The results clearly support the known-groups validity of the Contamination, Checking, Obsessions, and Hoarding subscales.Test re-test reliability among OCD groups is high, with all coefficients 0.9 or above after 47 days. For the student sample, however, test retest reliability was poor (0.5 to 0.6).

Interpretation
Results consist of a total raw score which is between 0 and 220, and 6 subscale scores:

Contaminations (12 items, scores between 0 and 48)
Checking (6 items, scores between 0 and 24)
Obsessions (12 items, scores between 0 and 48)
Hoarding (7 items, scores between 0 and 28)
Just right (12 items, scores between 0 and 48)
Indecisiveness (6 items, scores between 0 and 24)

In addition to the raw scores, results are presented in terms of percentile ranks compared to an OCD group, anxious/depressed group (AD), community adults (CA), and a student (S) sample. Percentile ranks for the community adults group should be interpreted with caution as the validity group has a low sample size (n=39). High percentiles indicate high levels of symptoms compared to comparison group.

Developer
Thordarson, D.S., Radomsky, A.S., Rachman, S., Shafran, R., Sawchuk, C.N., Hakstian, A.R. (2004). The Vancouver Obsessional Compulsive Inventory (VOCI). Behaviour Research & Therapy, 42(11), 1289-1314