Quick screen of patients’ numeracy and document literacy skills: the factor structure of the Newest Vital Sign

Figures & data

Table 1 Descriptive statistics of the participants, separated by samples analyzed in EFA and CFA

Variables	Total (n = 174)		EFA (n = 87)		CFA (n = 87)
	n (%)	Mean (SD)	n (%)	Mean (SD)	n (%)	Mean (SD)
Age		58.7 (12.8)		61.2 (11.0)		56.2 (14.0)
Gender
Female	100 (57.5)		51 (58.6)		49 (56.3)
Male	74 (42.5)		36 (41.4)		38 (43.7)
Race
White	118 (67.8)		62 (71.3)		56 (64.4)
Black	43 (24.7)		18 (20.7)		25 (28.7)
Other	13 (7.5)		7 (8.0)		6 (6.9)
Education
High school or less	66 (37.9)		31 (35.6)		35 (40.2)
Greater than high school	108 (62.1)		56 (64.4)		52 (59.8)
Health literacy		3.7 (2.0)		3.7 (2.0)		3.7 (2.0)
Limited (score = 0–1)	31 (17.8)		17 (19.5)		14 (16.1)
Marginal (score = 2–3)	39 (22.4)		18 (20.7)		21 (24.1)
Adequate (score = 4–6)	104 (59.8)		52 (59.8)		52 (59.8)
Numeracy (full score = 4)		2.3 (1.5)		2.2 (1.6)		2.3 (1.5)
Document literacy (full score = 2)		1.5 (0.8)		1.5 (0.8)		1.4 (0.9)

Abbreviations: EFA, exploratory factor analysis; CFA, confirmatory factor analysis.

Table 2 Reliability test of the NVS (n = 174)

Item	Question	Mean (SD)	Corrected item-total correlation	Cronbach’s alpha if item deleted
Item 1	If you eat the entire container, how many calories will you eat?	0.70 (0.46)	0.59	0.77
Item 2	If you are allowed to eat 60 g of carbohydrates as a snack, how much ice cream could you have?	0.61 (0.49)	0.64	0.76
Item 3	Your doctor advises you to reduce the amount of saturated fat in your diet. You usually have 42 g of saturated fat each day, which includes one serving of ice cream. If you stop eating ice cream, how many grams of saturated fat would you be consuming each day?	0.48 (0.50)	0.54	0.78
Item 4	If you usually eat 2,500 calories in a day, what percentage of your daily value of calories will you be eating if you eat one serving?	0.47 (0.50)	0.51	0.79
Item 5	Is it safe for you to eat this ice cream?	0.77 (0.42)	0.49	0.79
Item 6	(Ask only if the patient responds “no” to question 5): Why not?	0.70 (0.46)	0.62	0.76

Note: Cronbach’s alpha was 0.80 for the total scale.

Abbreviation: NVS, Newest Vital Sign.

Table 3 Inter-item correlations of the NVS (n = 174)

Item	Item 1	Item 2	Item 3	Item 4	Item 5	Item 6
Item 1	1.00
Item 2	0.57	1.00
Item 3	0.43	0.48	1.00
Item 4	0.43	0.52	0.41	1.00
Item 5	0.26	0.26	0.28	0.18	1.00
Item 6	0.41	0.40	0.35	0.29	0.84	1.00

Notes: Cell entries are Pearson’s correlation coefficient. Refer to Table 2 for the contents of the questions from item 1 to item 6.

Abbreviation: NVS, Newest Vital Sign.

Table 4 Component matrix after oblique rotation in EFA (n = 87)

Item	Question	Factor 1 rotated component loading	Factor 2 rotated component loading
Item 1	If you eat the entire container, how many calories will you eat?	0.666	−0.211
Item 2	If you are allowed to eat 60 g of carbohydrates as a snack, how much ice cream could you have?	0.769	−0.042
Item 3	Your doctor advises you to reduce the amount of saturated fat in your diet. You usually have 42 g of saturated fat each day, which includes one serving of ice cream. If you stop eating ice cream, how many grams of saturated fat would you be consuming each day?	0.605	−0.156
Item 4	If you usually eat 2,500 calories in a day, what percentage of your daily value of calories will you be eating if you eat one serving?	0.725	0.176
Item 5	Is it safe for you to eat this ice cream?	−0.065	−0.907
Item 6	(Ask only if the patient responds “no” to question 5): Why not?	0.191	−0.843

Notes: Factor 1 is identified as the numeracy component of health literacy. Factor 2 is identified as the document literacy component of health literacy.

Abbreviation: EFA, exploratory factor analysis.