A Clinical Comparison, Simulation Study Testing the Validity of SIMS and IOP-29 with an Italian Sample

  • Luciano Giromini
  • Donald J. Viglione
  • Claudia Pignolo
  • Alessandro Zennaro


The Inventory of Problems–29 (IOP-29) was recently introduced as a brief, easy-to-use measure of non-credible mental and cognitive symptoms that may be applied to a wide variety of contexts or clinical conditions. The current study compared its validity in discriminating bona fide versus feigned (via experimental malingering paradigm) psychopathology against that of the Structured Inventory of Malingered Symptomatology (SIMS). Specifically, 452 Italian adult volunteers participated in this study: 216 were individuals with mental illness who were asked to take the SIMS and IOP-29 honestly, and 236 were nonclinical participants (experimental simulators) who took the same two tests with the instruction to feign a psychopathological condition. Two main, broad categories of symptom presentations were investigated: (a) psychotic spectrum disorders and (b) anxiety, depression, and/or trauma-related disorders. Data analysis compared the effect sizes of the differences between the patients and experimental simulators, as well as the AUC and classification accuracy statistics for both the SIMS and IOP-29. The results indicate that the IOP-29 outperformed the SIMS, with the differences between the two tools being more notable within the psychotic (IOP-29 vs. SIMS: d = − 1.80 vs. d = − 1.06; AUC = .89 vs. AUC = .79) than within the anxiety, depression, and/or trauma related subgroup (IOP-29 vs. SIMS: d = − 2.02 vs. d = − 1.62; AUC = .90 vs. AUC = .86). This study also demonstrates that the IOP-29, with its single cutoff score, is generalizable culturally and linguistically from the USA (English) to Italy (Italian).


Inventory of Problems SIMS Malingering Psychosis Anxiety Depression 



We thank Drs. Giuseppe Maina, Karla Martino, Vincenzo Villari, Daniele Zizolfi, and Salvatore Zizolfi for their help in recruiting the clinical sample. We also thank Carlotta Brega, Giulia Carnino, Sonia Di Pietro, Celeste Gualinetti, Silvia Longo, Simone Manso, Sara Marchini, Edoardo Pepe, Silvia Pitirra, and Leonardo Stefanelli for their help in the data collection.

Compliance with Ethical Standards

Conflict of Interest

When this study was designed and realized, none of the authors had any conflict of interest. However, Luciano Giromini and Donald J. Viglione are currently in the process of creating a Limited Liability Company for the commercial use of the IOP-29. Conversely, Claudia Pignolo and Alessandro Zennaro continue to have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of PsychologyUniversity of TurinTurinItaly
  2. 2.California School of Professional PsychologyAlliant International University - San DiegoSan DiegoUSA

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