Measuring psychosis proneness in a nonclinical Korean population: is the Peters et al Delusions Inventory useful for assessing high-risk individuals?
OBJECTIVE
We examined the psychometric properties of the Korean version of the Peters et al Delusions Inventory (PDI) 40 and investigated the distribution of delusional ideation in a nonclinical population. We also used the item response theory to evaluate the usefulness of the PDI in measuring the risk for psychosis.


METHODS
A total of 310 nonclinical individuals completed the Korean PDI-40, the Magical Ideation Scale (MIS), and the Schizotypal Personality Scale (STA). In addition, 60 psychotic inpatients with delusions completed the PDI-40. Among 310 individuals, 124 participated in a follow-up study 6 months after completing their original questionnaire.


RESULTS
The PDI-40 revealed a slightly skewed distribution, but the score range was similar to that of the British population. Scores were negatively correlated with age, but no sex differences were found. The Korean PDI-40 exhibited good internal consistency and test-retest reliability. The PDI was significantly correlated with the MIS and the STA. Ten components were extracted through a principal component analysis with varimax rotation. The test results using item response theory revealed 39 items as the items which individuals with very high level of psychosis proneness will answer as "yes." Moreover, all items yielded "above moderate" discrimination in terms of psychosis proneness.


CONCLUSIONS
We confirmed the reliability and validity of the Korean PDI-40. The usefulness of the PDI-40 in a nonclinical population was replicated in the Korean sample. The PDI-40 can be used as an informative device when investigating "psychosis proneness" in a group at high risk for psychosis.
Jung
Hee Yeon
HY
Department of Psychiatry and Behavioral Science, and Institute of Human Behavioral Medicine, Seoul National University College of Medicine, Seoul 110-744, Republic of Korea.
Chang
Jae Seung
JS
Yi
Jung Seo
JS
Hwang
Samuel
S
Shin
Hyun-Kyun
HK
Kim
Jong Hoon
JH
Cho
In Hee
IH
Kim
Yong Sik
YS
D000293:Adolescent; D000328:Adult; D000368:Aged; D044466:Asian People / Q000208:ethnology*; D003702:Delusions / Q000175:diagnosis* / Q000208:ethnology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011618:Psychotic Disorders / Q000175:diagnosis* / Q000208:ethnology* / Q000523:psychology; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires