Validity of a Four-Item Household Water Insecurity Experiences Scale for Assessing Water Issues Related to Health and Well-Being

The original 12-item scale was designed using classical test theory to assess all components of household water insecurity in the prior 4 weeks. Responses to each item were summed to create a continuous score (range: 0-36). A shortened version of the HWISE Scale, the HWISE-4 Scale, was sought to be developed to promote its use in surveys with stringent criteria for retaining or adding new items. The HWISE-4 Scale was designed to be equivalent across contexts, easily answerable, capture a range of severity, and assess key constructs (availability, access, use, and reliability) of water insecurity. The scale was evaluated using data from 9,261 households in 25 LMICs. The four-item subset of the HWISE-4 Scale consisted of items assessing "worry," "changing plans," "limited drinking water," and "inability to wash hands" because of problems with water. This subset was highly correlated with full HWISE Scale scores (correlation coefficient: 0.949-0.980) and introduced minimal additional error (root mean square error: 2.13-2.68). Criterion validity was demonstrated, and a cut point of ≥ 4 correctly classified more than 91% of households as water secure or insecure. The HWISE-4 Scale was evaluated for its predictive accuracy, criterion validity, and sensitivity-specificity. Predictive validity was assessed by regressing food insecurity, perceived stress, satisfaction with water situation, and perceived water standing in the community on subset scores. Convergent validity was assessed by examining the association between subset scores and time to drinking water source. Discriminant validity was tested using differentiation between "known groups"; specifically, whether subset scores differed between those who did and did not report injury during water acquisition. The results showed that the four-item subset of the HWISE-4 Scale was a valid measure of household water insecurity. The scale was positively associated with full HWISE Scale scores, and a cut point of ≥ 4 correctly classified more than 91% of households as water secure or insecure. The HWISE-4 Scale can be used in LMICs to inform decisions about how to most effectively target resources and evaluate public health interventions.