OASys PD Screen

The Offender Assessment System (OASys) contains within it a number of specific questions which can be selected to screen for personality disorder. The tool consists of 10 items from OASys which bear considerable resemblance to diagnostic features of antisocial personality disorder and psychopathy. In addition to this, some additional personality disorder indicator items have been included.

OASys PD screen

  1. One of more convictions aged under 18 years
    Violence/threat of violence
  2. coercion
  3. Excessive use of violence/sadistic violence
  4. Recognises victim impact?
  5. Financial over reliance on friends, family, others for support
  6. Predatory lifestyle
  7. Reckless/risk taking
  8. Childhood behaviour problems
  9. Impulsivity
  10. Aggressive/controlling behaviour.
  11. Additional personality disorder item indicators
    1. Childhood Difficulties
    2. History of mental health difficulties
    3. Self harm/ suicide attempts
    4. Challenging behaviour


The presence of 8 or more items might indicate raised concerns.

The OASys guidance indicates that a specialist PD Pathway referral should be identified and made if offender scores positively on all or most items. The presence of eight or more items indicates consideration of a referral to a more specialist treatment intervention. A scoring checklist for the OASys PD screen with all the items and scoring instructions can be found here

Some important points to remember about the OASys PD screen:

  • High numbers of offenders reach the cut off. It is currently estimated that over 30% of offenders within probation’s caseload score at or above a suggested cut off of eight or more of the items endorsed.
  • It will only screen for antisocial/psychopathic traits and will not screen for characteristics of other disorders. So other types of personality disorder may be present even of the OASys PD scores are not raised.
  • Higher overall scores are likely to reflect a more severe antisocial presentation.

A note on the use of screening tools

There are a number available for personality disorder. Along with the OASys PD screen there is the International Personality Disorder Examination (IPDE) screen, P-Scan (for psychopathy) and the Standard Assessment of Personality – Abbreviated Scale (SAPAS). Of these, only SAPAS has been tested for validity (Lincoln University) with a Probation Trust managed population. Screening tools must always be used with extreme caution. In using any screen it is important to consider:

  1. Purpose – what exactly is it designed to screen for and in what setting?
  2. Competence – what qualifications and skills are required for its use?
  3. Validity – what does the tool claim to do? What evidence is there for its effectiveness? How likely is it to be accurate in terms of who it identifies and who it misses?
  4. Next steps – a screen is exactly what it says it is. It will identify a proportion of people who meet certain criteria; it will also miss some. Screens should only be used when there is clear guidance as to what happens next, for example, further assessments or advice sought from other professionals. Firm conclusions should never be drawn; the results never quoted in reports. Their only purpose is to guide the practitioner to further action.