Rhodes Index of Nausea and Vomiting--Form 2 in pregnant women. A confirmatory factor analysis

BACKGROUND: Despite widespread application of Rhodes Index of Nausea and Vomiting-Form 2 (INV2) in practice and research, empirical analyses have not been consistently performed to verify the a priori factors that guided the subclass construction of the symptoms. OBJECTIVES: To examine the dimensional structure of Rhodes INV in a sample of pregnant women. METHOD: Data were collected from 152 pregnant women who were experiencing some degree of nausea and vomiting during early pregnancy and analyzed using structural equation modeling techniques. Five competing measurement structures were tested and compared. The structure (model) that provided the closest fit to the data was selected and relationships (factor loadings) between the constructs and indicators were established. RESULTS: The model fitting the data the closest was a three-factor structure measuring nausea, vomiting, and retching as three separate, but correlated dimensions. The factor loadings were high (0.73-0.96) and significant (p < .001). The model treating nausea and vomiting as a one-factor concept as well as the model including two factors named symptom occurrence and symptom distress did not fit the data. CONCLUSION: Rhodes INV2 is a valid measurement tool if subscales are formed to reflect the multidimensional structure of nausea and vomiting in pregnancy.