An assessment of the test–retest reliability of the New Nordic Diet score

Figures & data

Table 1 The components underlying the construction of the subscales within the NND score (n=67)

Subscale	Related question(s)	Response alternatives and coding	Calculations (min–max)	Median=cut-off	Dietary behavior associated with scoring
1: Meal pattern	How often do you eat - breakfast - lunch - dinner - evening meal/supper	Never=0 Less than once a week=0.5 Once a week=1 Twice a week=2 Three times a week=3 Four times a week=4 Five times a week=5 Six times a week=6 Every day=7	Sum of answers to the four questions (0–28)	Test: 24.0 Retest: 24.0	Test: ≤24.0=0 ≥25.0=1 Retest: ≤24.0=0 ≥25.0=1
2: Nordic fruits	How often do you eat typical Nordic fruits (apple, pear, plum)	Never=0 Less than once a week=0.5 Once a week=1 Twice a week=2 Three times a week=3 Four times a week=4 Five times a week=5 Six times a week=6 Every day=7 Several times a day=10	No calculation (0–10)	Test: 4.0 Retest: 4.0	Test: ≤4.0=0 ≥5.0=1 Retest: ≤4.0=0 ≥5.0=1
3: Root vegetables	How often do you eat root vegetables (e.g. carrot, rutabaga, onion)?	Never=0 up to Several times a day=10	No calculation (0–10)	Test: 5.0 Retest: 4.0	Test: ≤5.0=0 ≥6.0=1 Retest: ≤4.0=0 ≥5.0=1
4: Cabbages	How often do you eat cabbages (e.g. cauliflower, broccoli, brussel sprouts, kale)?	Never=0 up to Several times a day=10	No calculation (0–10)	Test: 3.0 Retest: 3.0	Test: ≤3.0=0 ≥4.0=1 Retest: ≤3.0=0 ≥4.0=1
5: Potatoes vs. rice/pasta	How often do you eat - potatoes - rice - pasta	Never=0 up to Several times a day=10	Frequency of eating potatoes relative to eating rice and pasta combined: potatoes/(rice+pasta) (0–100)	Test: 0.49 Retest: 0.49	Test: <0.49=0 ≥0.49=1 Retest: <0.49=0 ≥0.49=1
6: Whole grain breads vs. white breads	How often do you eat - white breads/bread rolls - whole grain breads - whole grain hard breads	Never=0 up to Several times a day=10	Frequency of eating whole grain breads and hard breads combined relative to eating refined breads: (whole grain breads+whole grain hard breads)/refined breads (0–200)	Test: 14.67 Retest: 12.00	Test: ≤14.67=0 >14.67=1 Retest: ≤12.0=0 >12.0=1
7: Oatmeal porridge	How often do you eat oatmeal porridge?	Never=0 up to Several times a day=10	No calculation (0–10)	Test: 1.0 Retest: 0.5	Test: <1.0=0 ≥1.0=1 Retest: ≤0.5=0 >0.5=1
8: Foods from the wild countryside	How often do you eat - game (e.g. moose, reindeer, deer) - lean fish (e.g. cod, caley, haddock) - fatty fish (e.g. mackerel, herring, halibut) - other seafood (e.g. shrimps, crabs, mussels) - berries	Never=0 up to Several times a day=10	Sum of answers to the five questions (0–50)	Test: 4.5 Retest: 4.5	Test: ≤4.5=0 ≥5.0=1 Retest: ≤4.5=0 ≥5.0=1
9: Milk vs. juice	How often do you drink - milk - fruit juice without added sugar	Never=0 up to Several times a day=10	Frequency of drinking milk relative to drinking fruit juice: milk/juice (0–100)	Test: 1.37 Retest: 0.99	Test: ≤1.37=0 >1.37=1 Retest: ≤0.99=0 >0.99=1
10: Water vs. sugar/artificially sweetened beverages	How often do you drink - water - sugar sweetened beverages - artificially sweetened beverages	Never=0 up to Several times a day=10	Frequency of drinking water relative to drinking sugar sweetened beverages and artificially sweetened beverages combined: water/(sugar sweetened beverages+artificially sweetened beverages) (0–100)	Test: 4.76 Retest: 4.38	Test: ≤4.76=0 >4.76=1 Retest: <4.38=0 ≥4.38=1

NND, New Nordic Diet.

Table 2 Test–retest reliability of the 10 subscales and of the total NND score (n=67)

The 10 subscales constituting the NND score	Spearman's rank order correlation	Kappa measure of agreement (dichotomized subscales)	Percent agreement between test and retest (dichotomized subscales)
1: Meal pattern	0.78	0.70	85
2: Nordic fruits	0.76	0.60	81
3: Root vegetables	0.71	0.63	82
4: Cabbages	0.54	0.32	67
5: Potatoes vs. rice/pasta	0.70	0.67	84
6: Whole grain breads vs. white breads	0.62	0.52	76
7: Oatmeal porridge	0.84	0.67	84
8: Foods from the wild countryside	0.70	0.51	76
9: Milk vs. juice	0.84	0.76	88
10: Water vs. sugar/artificially sweetened beverages	0.79	0.43	72
NND score	0.80^a	0.52^b	69^b

NND, New Nordic Diet.

P-values for all analyses were <0.001.

^aPearson correlation coefficient is used for the NND score.

^bTrichotomized score.