Padua Inventory – Washington State University Revision (PI-WSUR)

Abstract

The Padua Inventory – Washington State University Revision (PI-WSUR) is an extensively validated 39-item self-report questionnaire designed to assess the presence and severity of obsessive-compulsive disorder (OCD) symptoms while minimizing empirical overlap with general anxiety and depressive distress. Developed by G. Leonard Burns, Sue Keortge, Gary M. Formea, and Laura G. Sternberger in 1996, the PI-WSUR represents a critical psychometric refinement of Ezio Sanavio’s original 60-item Padua Inventory (PI; Sanavio, 1988). The original scale was widely critiqued for including items tapping general trait worry, negative affect, and anxious apprehension, thereby inflating associations with generalized anxiety disorder and major depressive disorder. Through rigorous exploratory and confirmatory factor analyses, Burns and colleagues eliminated 21 confounding items, yielding a refined five-factor measurement structure: (1) Contamination obsessions and washing compulsions (10 items), (2) Dressing/grooming compulsions (3 items), (3) Checking compulsions (10 items), (4) Obsessional thoughts of harm to self/others (7 items), (5) Obsessional impulses to harm self/others (9 items). Respondents rate each item along a 5-point Likert scale ranging from 0 (“Not at all”) to 4 (“Very much”), yielding dimensional subscale indices and a cumulative global score ranging from 0 to 156. Across non-clinical and psychiatric cohorts, the PI-WSUR demonstrates superior psychometric stability, characterized by exceptional internal consistency (Cronbach’s α ranging from .77 to .90 across subscales; total scale α ≥ .92), high test-retest reliability across short-term and multi-week intervals (r = .76 to .86), and pronounced divergent validity against validated measures of worry such as the Penn State Worry Questionnaire (PSWQ). This revision remains a gold-standard instrument in empirical clinical psychology, neuropsychiatry, and cognitive-behavioral trials.

Keywords

Padua Inventory, PI-WSUR, Obsessive-Compulsive Disorder, Psychometrics, Factor Structure, Contamination Obsessions, Checking Compulsions, Harm Impulses, Trait Worry, Differential Diagnosis

Authors

The Padua Inventory – Washington State University Revision was conceptualized and psychometrically standardized by a team of clinical psychologists and researchers at Washington State University (Pullman, Washington, USA):

• G. Leonard Burns, Ph.D. — Department of Psychology, Washington State University, Pullman, WA. Dr. Burns has served as a preeminent psychometrician and clinical psychologist specializing in the assessment of child and adult psychopathology, internalizing and externalizing symptom dimensions, and structural equation modeling of dimensional clinical phenomena. (Corresponding Address: Department of Psychology, Washington State University, Pullman, WA 99164-4820, USA).
• Sue Keortge, M.S. — Department of Psychology, Washington State University, Pullman, WA. Contributed fundamentally to the structural modeling, psychometric item analysis, and scale derivation studies.
• Gary M. Formea, Ph.D. — Department of Psychology, Washington State University, Pullman, WA. Focused on the behavioral conceptualization of obsessive-compulsive manifestations and comparative diagnostic discriminant validity.
• Laura G. Sternberger, Ph.D. — Department of Psychology, Washington State University, Pullman, WA. Investigator in the clinical validation of obsessive-compulsive symptom domains and negative affectivity differentiation.

Purpose

The primary clinical and psychometric impetus for creating the Padua Inventory – Washington State University Revision (PI-WSUR) was the urgent need to address the discriminant validity shortcomings of early obsessive-compulsive assessment instruments. Historically, self-report tools in this domain—such as the Maudsley Obsessional Compulsive Inventory (MOCI) and the original 60-item Padua Inventory (Sanavio, 1988)—were groundbreaking in mapping the heterogeneous phenomenological landscape of OCD. However, extensive clinical and non-clinical trials revealed that these early metrics shared unacceptable levels of shared variance with generalized anxiety, dysphoria, and catastrophic worry. Clinicians repeatedly observed that patients with generalized anxiety disorder (GAD) or major depressive episodes obtained clinically elevated scores on the original Padua Inventory despite possessing no authentic ego-dystonic obsessions or ritualized compulsions.

Burns and colleagues (1996) recognized that this conceptual contamination stemmed from items that conflated true clinical obsessions with pervasive, ego-syntonic depressive rumination and generalized anxious worry. For example, questions assessing excessive concern over personal competence, general health anxieties, and existential guilt tended to load heavily on global negative affect rather than specific obsessive-compulsive psychopathology. Consequently, the PI-WSUR was engineered to systematically isolate distinct obsessive and compulsive symptom dimensions while pruning those items that correlated excessively with instruments measuring trait worry, such as the Penn State Worry Questionnaire (PSWQ).

In contemporary clinical workflows, the PI-WSUR serves multiple functional purposes. First, it enables precise baseline symptom profiling across five discrete behavioral and cognitive domains. Clinicians can determine whether a patient’s clinical presentation is predominantly governed by motoric rituals (e.g., compulsive checking, prolonged washing routines, elaborate dressing rituals) or covert mental phenomena (such as intrusive catastrophic mental imagery or egodystonic violent/taboo impulses). This dimensional parsing is invaluable for designing targeted Exposure and Response Prevention (ERP) protocols, where behavioral hierarchies must be tailored to specific threat stimuli and neutralizing behaviors. Second, the scale is sensitive to treatment-induced alterations over time, allowing researchers and practitioners in clinical trials to monitor subscale-specific responses to cognitive-behavioral therapies and pharmacotherapies such as selective serotonin reuptake inhibitors (SSRIs).

Psychological Construct

The PI-WSUR measures the multidimensional construct of obsessive-compulsive psychopathology. Contemporary cognitive and psychiatric conceptualizations view OCD not as a unitary diagnostic category, but rather as an etiologically complex syndrome characterized by distinct yet interrelated symptom dimensions. The 39 items of the PI-WSUR partition this psychopathological spectrum into five well-defined dimensions:

1. Contamination Obsessions and Washing Compulsions (Items 1–10)

This subscale evaluates intrusive distress, disgust, and catastrophic threat appraisals regarding exposure to physical contaminants, pathogens, bodily fluids (perspiration, saliva, urine), and public items touched by unfamiliar individuals, as well as the resulting functional neutralization behaviors. It captures both cognitive appraisals (“I think even slight contact with bodily secretions… may contaminate my clothes or somehow harm me”) and elaborate compensatory cleansing compulsions (“If I touch something I think is ‘contaminated’ I immediately have to wash or clean myself”). The focus is specifically anchored in irrational contagion fears rather than realistic hygiene precautions.

2. Dressing/Grooming Compulsions (Items 11–13)

Comprising a focused 3-item triad, this subscale isolates ritualized motor sequences surrounding daily bodily maintenance routines. It indexes rigid, rule-bound adherence to stereotyped motor patterns when donning clothing, undressing, washing, or preparing for sleep (“I feel obliged to follow a particular order in dressing, undressing and washing myself”; “Before going to bed I have to hang up or fold my clothes in a special way”). These behaviors are typically driven by a need for symmetry, perfectionism, or an unyielding internal sense of completion (“just right” sensations) rather than contamination concerns.

3. Checking Compulsions (Items 14–23)

This 10-item dimension measures stereotypic repetitive verification behaviors elicited by profound cognitive doubt, responsibility appraisals, and fears of preventable catastrophe. Items assess repetitive inspections of locks, domestic appliances, water/gas valves, letters, and forms (“I check and re-check gas and water taps and light switches after turning them off”; “I return home to check doors, windows, drawers, etc. to make sure they are properly shut”). Crucially, the subscale also taps the metacognitive core of checking rituals: severe subjective doubt regarding one’s own episodic memory and actions (“Sometimes I am not sure I have done things which in fact I know I have done”).

4. Obsessional Thoughts of Harm to Self/Others (Items 24–30)

This 7-item dimension captures intrusive, recurrent mental imagery and thoughts concerning disastrous consequences, unintended damage, or personal responsibility for catastrophic events. Unlike general anxiety worry, these cognitions are characterized by inflated responsibility, magical ideation, and severe emotional distress (“When I hear about a disaster, I think somehow it is my fault”; “I imagine catastrophic consequences as a result of absentmindedness or minor errors which I make”). The subscale operationalizes the cognitive misinterpretation of intrusive thoughts as portending imminent, preventable tragedies.

5. Obsessional Impulses to Harm Self/Others (Items 31–39)

Spanning 9 items, this dimension evaluates ego-dystonic, involuntary urges or impulses to execute shocking, taboo, aggressive, or self-destructive acts. Examples include intrusive urges to jump from precipitous heights (“When I look down from a bridge or a very high window, I feel an impulse to throw myself into space”), sudden violent impulses directed toward vulnerable individuals (“I sometimes have an impulse to hurt defenseless children or animals”), and antisocial impulses such as spontaneous shoplifting or property destruction. Crucially, in genuine obsessive-compulsive manifestations, these impulses evoke profound horror and moral revulsion; individuals do not derive pleasure from these cognitions and vigilantly guard against enacting them.

Theoretical Framework

The construction and refinement of the PI-WSUR are grounded in cognitive-behavioral and information-processing paradigms of obsessive-compulsive spectrum disorders, primarily formulated by pioneers such as Stanley Rachman, Paul Salkovskis, and David M. Clark.

According to Rachman’s (1971, 1997) cognitive formulation of obsessions, intrusive thoughts, images, and impulses are almost universally experienced across non-clinical populations. Empirical research indicates that over 80% to 90% of healthy individuals report occasional intrusive mental events featuring themes of contamination, sudden violence, or catastrophic errors. However, clinical obsessions develop when an individual interprets these intrusions as personally meaningful, catastrophic, or revealing of a covert moral defect. Salkovskis expanded this framework through his theory of inflated responsibility (Salkovskis, 1985; Salkovskis et al., 2000), positing that individuals with OCD operate under a core cognitive distortion: the belief that one possesses the pivotal power to cause or prevent catastrophic harm to oneself or others, and that failing to act to prevent such harm is morally equivalent to causing it deliberately.

Within this theoretical architecture, neutralizing behaviors—such as washing, checking, ordering, or covert mental rituals—are conceptualized as negative reinforcement mechanisms. When an intrusive cognition generates unbearable autonomic arousal and perceived threat, executing a ritualized motor compulsion temporarily alleviates distress and restores subjective safety. However, this immediate relief prevents natural cognitive extinction, reinforces cognitive misattributions, and paradoxically increases the subsequent frequency and salience of the intrusions.

Burns and colleagues (1996) utilized this cognitive-behavioral matrix to rectify a critical theoretical confound in the original Padua Inventory. Specifically, they drew a sharp theoretical boundary between obsessions and worry, guided by Borkovec’s cognitive models of Generalized Anxiety Disorder (Borkovec et al., 1983). Whereas worry is predominantly a verbal-linguistic, future-oriented cognitive process concerning realistic life domains (finances, health, career) that is experienced as relatively ego-syntonic, obsessions are intrusive, discrete, often visual or impulsive, and experienced as alien, morally repugnant, and deeply ego-dystonic. By empirically removing items that measured verbal-linguistic worry and general dysphoric contemplation, the PI-WSUR aligned its measurement model directly with pure cognitive theories of OCD psychopathology.

Validity

The construct, convergent, and discriminant validity of the PI-WSUR has been demonstrated across diverse academic, clinical, and cross-cultural psychometric investigations.

Construct and Factorial Validity

In the seminal psychometric investigation by Burns, Keortge, Formea, and Sternberger (1996), involving exploratory and confirmatory factor analyses on large cohorts of university students (N = 1,041), the hypothesized five-factor model demonstrated an outstanding fit to empirical data. The 39 retained items exhibited salient primary factor loadings (predominantly > .50) on their designated dimensions with negligible cross-loadings. Subsequent confirmatory factor analyses across independent clinical and community samples (e.g., Swinbourne & Touyz, 2007; Jazaieri et al., 2012) have consistently corroborated this robust five-factor infrastructure, proving its invariance across sexes and clinical severity strata.

Convergent Validity

The PI-WSUR demonstrates strong convergent associations with established clinical measures of obsessive-compulsive severity. It correlates robustly with the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), with correlation coefficients typically ranging between r = .55 and .72 across clinical cohorts. Strong convergent correlations are likewise documented with the Maudsley Obsessional Compulsive Inventory (MOCI) (r > .65) and the Obsessive-Compulsive Inventory-Revised (OCI-R) total and subscale scores (r = .60 to .81). Subscale-to-subscale convergence is particularly robust: the PI-WSUR Contamination subscale correlates highly with the OCI-R Washing subscale (r > .75), while the PI-WSUR Checking subscale demonstrates parallel congruence with the OCI-R Checking subscale (r > .78).

Discriminant and Divergent Validity

The defining triumph of the PI-WSUR lies in its proven discriminant superiority over the original 60-item instrument. When correlated with the Penn State Worry Questionnaire (PSWQ), the original Padua Inventory demonstrated problematic correlations often exceeding r = .55, indicating that roughly 30% of its variance was accounted for by generalized trait worry. In contrast, the PI-WSUR total score exhibits markedly attenuated correlations with the PSWQ (typically r = .28 to .34), and several subscales—most notably Dressing/Grooming and Checking—demonstrate near-zero to weak associations (r < .20). Furthermore, divergent validity has been established against measures of general depression (such as the Beck Depression Inventory-II, where correlations drop substantially compared to the original PI) and general trait anxiety (STAI-T), proving that the PI-WSUR isolates core OCD phenomenology from pervasive negative affectivity.

Reliability

The reliability profile of the PI-WSUR has been evaluated across non-clinical, subclinical, and DSM-diagnosed psychiatric cohorts, consistently yielding excellent internal consistency and temporal stability metrics.

Internal Consistency

In the initial psychometric standardization by Burns et al. (1996), internal consistency estimates (Cronbach’s alpha) for the PI-WSUR subscales evidenced high to excellent homogeneity:

• Contamination obsessions and washing compulsions: α = .88 to .90
• Dressing/grooming compulsions: α = .77 to .82 (notably robust given its brief 3-item length)
• Checking compulsions: α = .87 to .89
• Obsessional thoughts of harm to self/others: α = .81 to .84
• Obsessional impulses to harm self/others: α = .81 to .83
• Full Scale (Total 39 Items): α = .92 to .95

Subsequent psychometric evaluations across international adaptations—including German, Persian, Turkish, and Spanish translations—have replicated these parameters, documenting composite reliability coefficients that uniformly surpass standard clinical psychometric thresholds (α ≥ .80).

Test-Retest Stability

The temporal stability of the PI-WSUR has been verified across varying time intervals. Over a 2- to 4-week retest window in non-clinical cohorts, Pearson correlation coefficients ranged from r = .76 to .86 across the five subscales, with the total score exhibiting an aggregate stability coefficient of r = .87. In longitudinal observational designs tracking untreated OCD populations over 8- to 12-week spans, the instrument preserved significant consistency (r > .74), demonstrating that it captures enduring clinical traits rather than momentary mood fluctuations, while simultaneously exhibiting appropriate sensitivity to change following formal evidence-based clinical interventions.

Factor Analysis

The structural refinement of the original Padua Inventory into the PI-WSUR was executed using sophisticated multivariate psychometric analyses. Sanavio’s original 60-item instrument had revealed unstable four- or five-factor solutions across different cultures, with numerous items cross-loading heavily on uninterpretable general anxiety dimensions.

Exploratory Factor Analysis (EFA)

Burns and colleagues initiated their revision by subjecting the original item pool to exploratory factor analyses with oblique rotations (promax) in a development sample of undergraduate participants. Iterative factor analyses demonstrated that 21 items systematically failed to meet predefined retention criteria: they either displayed low primary loadings (< .40), severe cross-loadings (≥ .30 on secondary factors), or, critically, manifested high zero-order correlations with the Penn State Worry Questionnaire (PSWQ). These 21 items predominantly reflected existential health worries, general indecisiveness, interpersonal self-consciousness, and everyday moral concerns. Removal of these problematic items eliminated the confounding “general worry/distress” latent factor entirely.

Confirmatory Factor Analysis (CFA) and Model Fit

The resulting 39 items were subsequently tested in an independent validation sample using maximum likelihood Confirmatory Factor Analysis. The postulated correlated five-factor model demonstrated exceptional goodness-of-fit indices that markedly outperformed competing unifactorial or hierarchical models:

• Comparative Fit Index (CFI): .92 to .95 across multi-group validation cohorts
• Tucker-Lewis Index (TLI / NNFI): .91 to .94
• Root Mean Square Error of Approximation (RMSEA): .042 to .053 (90% Confidence Interval: [.038, .049]), well within established boundaries for close model fit (< .06)
• Standardized Root Mean Square Residual (SRMR): .048

Standardized factor loadings for individual items across all five latent variables were exceptionally robust. In the Contamination subscale, item loadings ranged from .54 to .81. The Checking subscale demonstrated loadings from .52 to .79. The Harm Thoughts dimension showed loadings between .51 and .76, while the Harm Impulses dimension displayed loadings from .48 to .78. Inter-factor correlations among the latent dimensions were moderate (ranging from r = .29 between Dressing/Grooming and Harm Impulses to r = .62 between Checking and Harm Thoughts), substantiating the theoretical perspective that while these symptom domains reflect a common overarching obsessive-compulsive spectrum, they operate as conceptually discrete psychological constructs.

Instrument / Measurement Tool

The structural, formal, and administrative specifications of the PI-WSUR are organized as follows:

• Test Type: Multi-dimensional self-report symptom rating scale / psychological inventory.
• Administration Format: Paper-and-pencil or secure computerized/digital clinical administration. Both individual and group administrations are valid.
• Respondent Population: Adults and adolescents aged 16 years and older; adapted versions exist for younger clinical groups.
• Completion Time: Approximately 8 to 12 minutes.
• Item Count: Exactly 39 items.
• Response Format: 5-point Likert scale formatted as:
  • 0 = Not at all
  • 1 = A little
  • 2 = Quite a lot
  • 3 = A lot
  • 4 = Very much
• Subscale Structural Breakdown:
  • Subscale 1: Contamination obsessions and washing compulsions (10 items: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; Score range: 0–40)
  • Subscale 2: Dressing/grooming compulsions (3 items: 11, 12, 13; Score range: 0–12)
  • Subscale 3: Checking compulsions (10 items: 14, 15, 16, 17, 18, 19, 20, 21, 22, 23; Score range: 0–40)
  • Subscale 4: Obsessional thoughts of harm to self/others (7 items: 24, 25, 26, 27, 28, 29, 30; Score range: 0–28)
  • Subscale 5: Obsessional impulses to harm self/others (9 items: 31, 32, 33, 34, 35, 36, 37, 38, 39; Score range: 0–36)
• Scoring Rules: All 39 items are positively scored in the direction of psychopathology; there are no reverse-coded items. Subscale scores are obtained by calculating the direct sum of the corresponding items. The cumulative Total Score is the sum of all 39 items (Theoretical Range: 0 to 156). Higher scores signify elevated subjective disturbance and greater symptom severity.

Permissions & Fee and Test Year

The Padua Inventory – Washington State University Revision was developed in 1995 and formally introduced to the international scientific community in 1996 via publication in the peer-reviewed journal Behaviour Research and Therapy.

Licensing and Accessibility: The PI-WSUR was placed by its original authors, G. Leonard Burns and colleagues, in the public academic domain for non-commercial clinical practice, scientific research, and educational applications. No licensing fees or royalty payments are mandated for non-commercial research or standard clinical diagnostic usage. Clinicians and researchers wishing to utilize the instrument in institutional settings are expected to cite the foundational validation publication (Burns et al., 1996). Commercial redistribution, integration into fee-based proprietary software systems, or commercial publication rights require formal authorization from the copyright holder and corresponding author (Dr. G. Leonard Burns, Department of Psychology, Washington State University).

References

• Borkovec, T. D., Robinson, E., Pruzinsky, T., & DePree, J. A. (1983). Preliminary exploration of worry: Some characteristics and processes. Behaviour Research and Therapy, 21(1), 9–16. https://doi.org/10.1016/0005-7967(83)90121-3
• Burns, G. L. (1995). Padua Inventory-Washington State University Revision. Pullman, WA: Author. (Available from G. Leonard Burns, Department of Psychology, Washington State University, Pullman, WA 99164-4820).
• Burns, G. L., Keortge, S., Formea, G. M., & Sternberger, L. G. (1996). Revision of the Padua Inventory of obsessive compulsive disorder symptoms: Distinctions between worry, obsessions, and compulsions. Behaviour Research and Therapy, 34(2), 163–173. https://doi.org/10.1016/0005-7967(95)00035-6
• Jazaieri, H., Goldin, P. R., & Gross, J. J. (2012). Treating social anxiety disorder with mindfulness-based stress reduction and cognitive behavioral therapy: Clinical outcomes and psychometric evaluations. Journal of Clinical Psychology, 68(7), 755–771. https://doi.org/10.1002/jclp.21867
• Rachman, S. (1971). Obsessional ruminations. Behaviour Research and Therapy, 9(3), 229–235. https://doi.org/10.1016/0005-7967(71)90008-8
• Rachman, S. (1997). A cognitive theory of obsessions. Behaviour Research and Therapy, 35(9), 793–802. https://doi.org/10.1016/S0005-7967(97)00040-5
• Salkovskis, P. M. (1985). Obsessional-compulsive problems: A cognitive-behavioural analysis. Behaviour Research and Therapy, 23(5), 571–583. https://doi.org/10.1016/0005-7967(85)90105-6
• Salkovskis, P. M., Wroe, A. L., Gledhill, A., Morrison, N., Forrester, E., Richards, C., Reynolds, M., & Thorpe, S. (2000). Responsibility attitudes and interpretations are characteristic of obsessive compulsive disorder. Behaviour Research and Therapy, 38(4), 347–372. https://doi.org/10.1016/S0005-7967(99)00071-6
• Sanavio, E. (1988). Obsessions and compulsions: The Padua Inventory. Behaviour Research and Therapy, 26(2), 169–177. https://doi.org/10.1016/0005-7967(88)90116-7
• Swinbourne, J. M., & Touyz, S. W. (2007). The co-morbidity of eating disorders and anxiety disorders: A review. Clinical Psychology Review, 27(4), 494–506. https://doi.org/10.1016/j.cpr.2006.11.006

Items of the Scale