The revised Healthy Purchase Index (r-HPI): a validated tool for exploring the nutritional quality of household food purchases

Background The Healthy Purchase Index (HPI) assesses the nutritional quality of food purchases (FP) from food group expenditure shares only. However, it was developed from the FP of a disadvantaged population. Objective To adapt and validate the HPI for a general population. Methods FP were obtained from a representative sample of French households (Kantar WorldPanel) subdivided into two subsamples. The first sample ( n = 4375) was used to adapt and validate the score; the second sample ( n = 2188) was used to test external validity. The revised-HPI (r-HPI) includes 2 subscores: the diversity subscore and the quality subscore. Diversity subscore points were awarded when expenditure shares were above the 25th percentile for 5 food groups (“Fruits”, “Vegetables”, “Starches”, “Dairy”, “Meat, Fish and Eggs”). Regression models between the expenditure shares of each food group and the Mean Adequacy Ratio (MAR) and the Mean Excess Ratio (MER) of FP were used to select quality subscore components and define cut-offs for point allocation. Construct validity was assessed on the first sample using Spearman’s correlations between the r-HPI and the four nutritional quality indicators (NRF9.3, MAR, MER, energy density), and also by comparing the r-HPI of monthly FP of sub-populations defined by criteria known to influence diet quality (age, gender, income, education) and between households having a monthly food basket of higher (MAR > median and MER and energy density 21%). The r-HPI (mean = 6.50 ± 3.58) was strongly correlated with NRF9.3, MAR, MER and energy density (0.59, 0.52, − 0.41 and − 0.65, respectively, p