Validity and reproducibility of the Prime Diet Quality Score (PDQS) against a four-day food diary in adults at risk of cardiovascular disease on the island of Ireland

There is an increasing need for valid, rapid diet screening tools. A significant association between the Prime Diet Quality Score (PDQS) and reduced risk of cardiovascular disease (CVD) has been demonstrated in the US but evidence of its use in Europe is lacking. The aim of this study was to amend the PDQS for a UK/Irish population and determine validity and reliability in those at risk of CVD. Participants were recruited via online adverts across the island of Ireland. The PDQS was amended for a UK/Irish population and participants completed PDQS and reference measure (4-day food diary (FD)) on two occasions. PDQS score was calculated directly from PDQS and indirectly from FDs. Validity was determined using Spearman correlation coefficients (SCCs) (r), intraclass correlation coefficients (ICCs) and weighted kappa. Reliability was determined using SCCs (r), ICCs, weighted kappa and coefficient of variation.

‘Data were available for n = 115 (Month 0) and n = 108 (Month 3) participants for validity and n = 110 for reliability assessment (PDQS completed at both timepoints)’. PDQS score from PDQS was significantly correlated with PDQS score from FDs at months 0 (r = 0.59, P < 0.01) and 3 (r = 0.65, P < 0.01), with similar associations observed via ICCs. Weighted kappa indicated moderate agreement. PDQS score at month 0 was significantly correlated with PDQS score at month 3 (r = 0.78, P < 0.01), with similar associations observed via ICCs. Weighted kappa indicated moderate agreement. Results indicate that the amended PDQS is a valid and reliable tool to determine diet quality in a UK/Irish population at risk of CVD.