Validation of the Dutch version of the itching cognitions questionnaire.

The purpose of this study was to examine the reliability and validity of the Dutch itching cognitions questionnaire (ICQ). This by origin German questionnaire, the Juckreiz Kognitons Fragebogen consists of two subscales: catastrophizing and helpless coping and problem-focused coping, and measures itch-related coping. The results were compared with the German and Japanese validation studies. The Dutch ICQ was completed by 171 patients with chronic pruritic skin diseases. Reliability was evaluated by determining internal consistency, mean inter-item correlation, and item-total correlation. Cronbach's alpha was .90 (catastrophizing and helpless coping) and .81 (problem-focused coping). The mean inter-item correlations for the subscales were .48 (catastrophizing and helpless coping) and .30 (problem-focused coping). The item-total correlations range from .57 to .76 (catastrophizing and helpless coping) and from .32 to .57 (problem-focused coping). Confirmatory factor analysis indicated a good fit of the model and support construct validity. Concurrent validity was determined by examining correlations of the ICQ with intensity of itching and scratching, depression, and anxiety. The correlations of the subscale catastrophizing and helpless coping with intensity of itching and intensity of scratching are .28 (p < .01) and .32 (p < .01), respectively. The correlation between the subscale problem-focused coping and intensity of itching is .23 (p < .01). No significant correlation exists between problem-focused coping and intensity of scratching. Correlations between both subscales and anxiety and depression vary from .33 to .58 (p < .01). It was concluded that the Dutch version of the ICQ is a reliable and valid instrument.