Reliability and convergent and discriminant validity of the Child Oral Health Impact Profile (COHIP Child’s version)
Authors: Broder Hillary L. , Wilson‐Genderson Maureen 
Published: July 2007

Objectives:  The purpose of the current study was to assess the reliability as well as the convergent and discriminant validity of the Child Oral Health Impact Profile (COHIP). The questionnaire consisted of five domains that assessed oral health, functional well‐being, social‐emotional well‐being, school environment, and self‐image. COHIP was designed to measure self‐reported oral health‐related quality of life (OHRQoL) of children between ages 8 and 15 years old, using both positively and negatively worded items.

Methods:  Children were recruited from pediatric, orthodontic, and craniofacial clinical settings in the USA and Canada. A comparison group of children not seeking dental treatment was recruited from two US elementary schools. Participants included 157 pediatric, 152 orthodontic and 110 patients with craniofacial anomalies, and 104 community‐based participants. Scale reliability was assessed with Cronbach’s alpha coefficient. Retest reliability was examined by intraclass correlation and paired t‐test for a subset of participants who did not report a health change. Discriminant validity was assessed in two ways: (i) the COHIP scores of the four groups of children (three clinical and one community‐dwelling) were compared by anova and (ii) for two of the clinical groups, the association between COHIP scores and clinical indices was calculated. Convergent validity was examined using partial Spearman correlations between COHIP scores and Global Health Ratings controlling for demographic variables.

Results:  The children (n = 523) averaged 11.6 years (SD = 1.60); 51.6 % were female; and represented diverse ethnicities (black = 22.4%, Latino = 32.1%, white = 35.1%, other 10.4%). Overall COHIP scores ranged from 28 to 135 (mean ± SD, 99.0 ± 19.2) for the children. Scale reliability for the overall COHIP was excellent: Cronbach’s alpha coefficient = 0.91 for the overall score. The test–retest reliability of the overall COHIP was also excellent (ICC = 0.84) and there was no statistically significant shift in scores over time. Discriminant validity was supported by significant differences (P = 0.003 overall COHIP) among the three clinical groups: the craniofacial group reported the lowest overall COHIP quality of life scores of the clinical groups. Within the pediatric dental group, children with greater dental decay reported lower COHIP scores suggesting a lower OHRQoL (r = −0.26, P = 0.02) and within the orthodontic group, children with larger overjet reported lower COHIP scores (r = −0.25, P = 0.005). Controlling for the effect of the participants’ age, gender, and ethnicity, the association between the overall COHIP score and Global Health rating was statistically significant (P < 0.05) and similar in strength for the three clinical groups (pediatric dental = 0.29, orthodontic = 0.23, and craniofacial = 0.24) and highest for the community group (0.36).

Conclusion:  The overall COHIP showed excellent scale reliability overall and test–retest reliability. Both discriminant and convergent validity of the COHIP were supported by the comparisons among and within the four groups of children. Further testing will examine the utility of the instrument in both clinical and epidemiological samples.