The inventory of problems-29 (IOP-29) in a US clinical sample

Area of Science:

• Psychological assessment
• Clinical psychology
• Personality testing

Background:

• Limited research exists on the Inventory of Problems-29 (IOP-29) using simulation designs and non-US samples.
• Previous studies have not evaluated the IOP-29's performance within US clinical populations.

Purpose of the Study:

• To assess the validity of the IOP-29 in US clinical samples.
• To compare the IOP-29's False Disorder Probability Score (FDS) with validity scales from the Minnesota Multiphasic Personality Inventory (MMPI).

Main Methods:

• 217 clinical patients completed the IOP-29 and MMPI (versions 2 or 3).
• Criterion validity of the IOP-29 FDS was assessed using correlations with MMPI validity scales.
• Diagnostic accuracy statistics were calculated to identify invalid response profiles.

Main Results:

• The IOP-29 FDS positively correlated with MMPI overreport scales (ρ = .24–.62) and negatively with underreport scales.
• At an FDS cutoff of ≥ .50, sensitivity was .72 and specificity was .88.
• Increasing the FDS cutoff to ≥ .58 improved specificity to .90 without affecting sensitivity, while a cutoff of ≥ .64 yielded .95 specificity but reduced sensitivity to .56.

Conclusions:

• The IOP-29 demonstrates utility as a measure of negative response bias in mixed US clinical samples.
• The recommended FDS cutoff of ≥ .50 is effective, with a slight increase needed for higher specificity.
• Further research is recommended using diverse clinical and forensic samples and varied methods for identifying invalid profiles.