3.1. Sample characteristics
As shown in , hoarding, OCD, and NCC participants did not differ in terms of gender, ethnicity (White/Nonwhite), employment status, or education (college graduate or greater). OCD participants were significantly younger on average than were hoarding or NCC participants. Hoarding participants were more likely than were OCD or NCC participants to describe themselves as disabled.
As expected, hoarding participants scored higher on all measures of compulsive hoarding (SI-R, CIR, OCI-R hoarding scale) than did OCD or NCC participants, who did not differ from each other. Hoarding participants also reported higher levels of depression (Mildy Depressed range on the BDI-II) than did OCD or NCC participants (Minimally Depressed range). Hoarding and OCD participants did not differ in levels of anxiety (Mildly Anxious range on the BAI), and both groups scored higher than did NCC participants (Minimally Anxious range). OCD participants scored higher than did NCC participants on all OCI-R scales (with the exception of hoarding); hoarding participants also scored higher than did NCC participants on the OCI-R subscales Checking, Neutralizing, Obsessing, and Ordering. Eleven (15%) of the hoarding participants were also diagnosed with OCD.
3.2. Internal consistency
Internal consistency (Cronbach's α) of the HRS-I completed in the clinic was high, α = 0.97. Inter-item correlations ranged from 0.77-0.91. At the home visit, internal consistency was also high, α = 0.96, with inter-item correlations ranging from 0.76-0.96.
3.3. Test-retest and cross-context reliability
Reliability analyses for HRS-I ratings completed in the clinic and at home are shown in . These reliability analyses vary across time (1 to 12 weeks), and across contexts (clinic vs. home). Given the differences between these two administrations, correlations were remarkably high (range 0.85 - 0.94 for corresponding items, and 0.96 for the total score). Partial correlations, controlling for the number of days elapsed between assessments, yielded similar results.
Test-Retest and Cross-Context Reliability of the Hoarding Rating Scale-Interview (HRS-I)
3.4. Known groups validity
depicts scores on the HRS-I for hoarding and non-hoarding participants. Groups differed significantly on each item and on the total HRS-I score. In the clinic analyses, Tukey HSD post hoc tests indicated that hoarding participants scored higher on all items and on the total score than did OCD or NCC participants, who did not differ from each other. Identical results were obtained during the home visit. These analyses were conducted again using analyses of covariance (ANCOVAs), controlling for age, gender (dummy coded), and race (White vs. NonWhite, dummy coded), with identical results (not shown).
Hoarding Rating Scale-Interview (HRS-I) item scores in the clinic and home visit for participants with compulsive hoarding, obsessive-compulsive disorder (OCD), and nonclinical controls (NCC).
Receiver Operating Characteristic (ROC) analysis was conducted to determine the capacity of the HRS-I items and total score to discriminate between hoarding and OCD participants. For items 1-5 and the total score, areas under the curve were 0.98 (standard error [SE] = 0.01), 0.98 (SE = 0.01), 0.93 (SE = 0.02), 0.99 (SE = 0.01), 0.98 (SE = 0.01), and 0.99 (SE = 0.01), respectively (all ps < 0.001), suggesting good discrimination. Analysis of the sensitivity and specificity of each potential cutoff score suggested that a cutoff score of 3 yielded optimal sensitivity and specificity for item 1 (sensitivity = 0.97, specificity = 0.97), item 4 (0.93 and 0.97), and item 5 (0.96 and 0.95). The optimal cutoff score for item 2 was 4 (0.92 and 0.93), and the optimal cutoff score for item 3 was 2 (0.93 and 0.80). For the total HRS-I score (sum of all 5 HRS-I items), the optimal cutoff score was 14 (0.97 and 0.97).
3.5. Convergent validity
Pearson correlations between HRS-I scores and the other measures of hoarding severity are shown in . Each HRS-I item, as well as the total score, correlated significantly and positively with each of the other hoarding measures in the clinic. The same pattern of results was found in the home visit. Results in either analysis did not change when controlling for age, gender (dummy coded), and race (dummy coded) using partial correlation coefficients (not shown). Examination of scatterplots (not shown) revealed no clear outliers.
Correlations between Hoarding Rating Scale-Interview (HRS-I) items in the clinic and home visit and other measures of hoarding.
3.6. Discriminant validity
To examine the relationship between the 3 corresponding HRS-I and SI-R subscales (Clutter, Difficulty Discarding, Acquisition), we computed partial correlations between each pair of subscales, while controlling for the other two SI-R subscales (see ). For clinic ratings, the HRS-I Clutter scale correlated only with SI-R Clutter when controlling for the other SI-R subscales. HRS-I Difficulty Discarding correlated significantly with SI-R Clutter and Difficulty Discarding (but not SI-R Acquiring). HRS-I Acquiring correlated significantly with SI-R Difficulty Discarding and Acquiring. All three HRS-I items showed the strongest relationship with their corresponding SI-R subscale. In-home ratings yielded a similar pattern (with the exception that HRS-I Acquiring did not correlate significantly with SI-R Difficulty Discarding), despite the fact that one measure (SI-R) was conducted in the clinic, and the other (HRS-I) was conducted later in the home. In both assessments, the general pattern is of a stronger association for like subscales than for unlike subscales.
Correlations between the 3 symptom items on the Hoarding Rating Scale-Interview (HRS-I) with corresponding subscales of the Saving Inventory-Revised (SI-R), controlling for other SI-R subscales
As indicates, The HRS-I items and total score did not show strong correlations with the Checking, Neutralizing, Obsessing, or Washing subscales of the OCI-R. HRS-I scores did correlate significantly with the OCI-R Ordering subscale, although the strength of the correlations was modest and substantially lower than were the correlations between the HRS-I and measures of hoarding depicted in . The HRS-I items and total score correlated significantly with depression and anxiety as measured by the BDI-II and BAI, although these correlations too were substantially lower than those in . This pattern of findings was replicated in the home visit. To examine the independence of these correlations, a stepwise regression analysis of the clinic variables was conducted, with OCI-R Ordering, BDI-II, and BAI scores as predictors, and HRS-I total score as the dependent variable. Of these three predictor variables, only BDI-II independently predicted HRS-I scores (b = 0.61, t = 8.79, p < .001). Thus, the modest relationship between ordering and HRS-I scores was no longer significant when controlling for depression.
Correlations between the Hoarding Rating Scale-Interview (HRS-I), completed in the clinic and during the home visit, and non-hoarding measures completed in the clinic