Parent Preferences and Perceptions of Milliliters and Teaspoons: Role of Health Literacy and Experience

Abstract

Background and objectives: A recent American Academy of Pediatrics policy statement recommends milliliter-exclusive dosing for pediatric liquid medications. Little is known about parent preferences regarding units, perceptions about moving to milliliters only, and the role of health literacy and prior milliliter-dosing experience.

Methods: Cross-sectional analysis of data collected as part of a randomized controlled study in 3 urban pediatric clinics (SAFE Rx for Kids study). English- and Spanish-speaking parents (n = 493) of children aged ≤8 years were randomized to 1 of 4 study arms and given labels and dosing tools which varied in label instruction format (text plus pictogram, text only) and units (milliliter only ["mL"], milliliter/teaspoon ["mL"/"tsp"]). Outcomes included teaspoon preference in dosing instructions and perceived difficulty with milliliter-only dosing. The predictor variable was health literacy (Newest Vital Sign; low [0-1], marginal [2-3], adequate [4-6]). The mediating variable was prior milliliter-dosing experience.

Results: Over two-thirds of parents had low or marginal health literacy. The majority (>70%) preferred to use milliliters, perceived milliliter-only dosing to be easy, and had prior milliliter-dosing experience; 11.5% had a teaspoon preference, 18.1% perceived milliliter-only dosing will be difficult, and 17.7% had no prior milliliter-dosing experience. Parents with lower health literacy had a higher odds of having a teaspoon preference (low vs adequate: adjusted odds ratio [AOR] = 2.9 [95% confidence interval [CI] 1.3-6.2]), and greater odds of perceiving difficulty with milliliter-only dosing (low vs adequate: AOR = 13.9 [95% CI 4.8-40.6], marginal vs adequate: AOR = 7.1 [95% CI 2.5-20.4]). Lack of experience with milliliter dosing partially mediated the impact of health literacy.

Conclusions: Most parents were comfortable with milliliter-only dosing. Parents with low health literacy were more likely to perceive milliliter-only dosing to be difficult; educational efforts will need to target this group to ensure safe medication use.

Keywords: ambulatory care; dosing errors; dosing units; health communication; health literacy; medication errors.

Figure 1. Recruitment and Enrollment of Study Participants

^a Parents consecutively approached in the clinic ^b Ran out of time after signing consent

Figure 2. Path Analysis: Lack of mL-Dosing Experience as a Mediator of Low Health Literacy-associated Teaspoon Preference and Perceived Difficulty with mL-only Instructions^a

Figure 2A. Lack of mL-Dosing Experience as a Mediator of Low Health Literacy-associated Teaspoon Preference Figure 2B. Lack of mL-Dosing Experience as a mediator of Low Health Literacy-associated Perceived Difficulty with mL-only Instructions Abbreviations: HL=health literacy ^a Baron and Kenny criteria for mediation met for both models: health literacy associated with dependent variables of interest [strong teaspoon preference and perceived difficulty with mL-only instructions] in analyses without lack of experience dosing with mL in model; health literacy associated with lack of experience dosing with mL; lack of experience associated with dependent variables; and association between health literacy and dependent variables reduced when lack of experience dosing with mL included in the model. Note wide confidence intervals in Figure 2 for relationship between health literacy and lack of mL-dosing experience due to skewed data, such that among those with adequate health literacy, 95% had experience with mL-dosing (for lack of experience vs. experience with mL-dosing, n's by health literacy level were: low: 38 vs. 96, marginal: 41 vs. 171, adequate: 6 vs. 128). ^b Health literacy assessed using the Newest Vital Sign (NVS). ^c Multiple logistic regression analysis adjusting for parent age and country of birth (US-born vs. non-US born), and health literacy. Note wide confidence interval in Figure 2B for the relationship between health literacy and perceived difficulty with mL-only dosing due to skewed data; among those with adequate health literacy, 97% did not perceive difficulty with mL-only dosing (for perceived difficulty vs. no difficulty, n's by health literacy level were: low: 89 vs. 45, marginal: 173 vs. 39, adequate: 130 vs. 4). ^d Multiple logistic regression analysis with lack of experience included in the model and adjusting for variables listed in footnote c. Note wide confidence interval in Figure 2B due to skewed data as described above. ^e Strong teaspoon preference created as a composite variable including parents who chose teaspoon/tsp for both 5 and 7.5 mL dose amounts. For strong teaspoon preference, low vs. marginal vs. adequate health literacy (n(%)): 26(19.4) vs. 16(7.6) vs.13(9.7), p=0.001. In the adjusted model predicting strong preference for teaspoon, other than health literacy, parent age and non-US country of birth (vs. US-born) were statistically significantly related (AOR=1.05[1.01-1.08] and AOR=2.3[1.2-4.4], respectively). With addition of experience dosing with mL in the model, both factors remained statistically significantly related (AOR=1.04[1.004-1.08] and AOR=2.2[1.2-4.2], respectively). ^f Perceived difficulty created as a composite variable with parents who selected very or somewhat hard with respect to mL-only dosing. For perceived difficulty, low vs. marginal vs. adequate health literacy (n(%)): 45(33.6) vs. 39(18.4) vs. 4(3.0), p<0.001. In the adjusted model predicting difficult with mL-only dosing, parent age [AOR=1.04[1.01-1.08] was the only variable that was statistically significantly related. With addition of experience dosing with mL in the model, parent age remained statistically significantly related (AOR=1.04[1.001-1.07]).

Figure 2. Path Analysis: Lack of mL-Dosing Experience as a Mediator of Low Health Literacy-associated Teaspoon Preference and Perceived Difficulty with mL-only Instructions^a

Figure 2A. Lack of mL-Dosing Experience as a Mediator of Low Health Literacy-associated Teaspoon Preference Figure 2B. Lack of mL-Dosing Experience as a mediator of Low Health Literacy-associated Perceived Difficulty with mL-only Instructions Abbreviations: HL=health literacy ^a Baron and Kenny criteria for mediation met for both models: health literacy associated with dependent variables of interest [strong teaspoon preference and perceived difficulty with mL-only instructions] in analyses without lack of experience dosing with mL in model; health literacy associated with lack of experience dosing with mL; lack of experience associated with dependent variables; and association between health literacy and dependent variables reduced when lack of experience dosing with mL included in the model. Note wide confidence intervals in Figure 2 for relationship between health literacy and lack of mL-dosing experience due to skewed data, such that among those with adequate health literacy, 95% had experience with mL-dosing (for lack of experience vs. experience with mL-dosing, n's by health literacy level were: low: 38 vs. 96, marginal: 41 vs. 171, adequate: 6 vs. 128). ^b Health literacy assessed using the Newest Vital Sign (NVS). ^c Multiple logistic regression analysis adjusting for parent age and country of birth (US-born vs. non-US born), and health literacy. Note wide confidence interval in Figure 2B for the relationship between health literacy and perceived difficulty with mL-only dosing due to skewed data; among those with adequate health literacy, 97% did not perceive difficulty with mL-only dosing (for perceived difficulty vs. no difficulty, n's by health literacy level were: low: 89 vs. 45, marginal: 173 vs. 39, adequate: 130 vs. 4). ^d Multiple logistic regression analysis with lack of experience included in the model and adjusting for variables listed in footnote c. Note wide confidence interval in Figure 2B due to skewed data as described above. ^e Strong teaspoon preference created as a composite variable including parents who chose teaspoon/tsp for both 5 and 7.5 mL dose amounts. For strong teaspoon preference, low vs. marginal vs. adequate health literacy (n(%)): 26(19.4) vs. 16(7.6) vs.13(9.7), p=0.001. In the adjusted model predicting strong preference for teaspoon, other than health literacy, parent age and non-US country of birth (vs. US-born) were statistically significantly related (AOR=1.05[1.01-1.08] and AOR=2.3[1.2-4.4], respectively). With addition of experience dosing with mL in the model, both factors remained statistically significantly related (AOR=1.04[1.004-1.08] and AOR=2.2[1.2-4.2], respectively). ^f Perceived difficulty created as a composite variable with parents who selected very or somewhat hard with respect to mL-only dosing. For perceived difficulty, low vs. marginal vs. adequate health literacy (n(%)): 45(33.6) vs. 39(18.4) vs. 4(3.0), p<0.001. In the adjusted model predicting difficult with mL-only dosing, parent age [AOR=1.04[1.01-1.08] was the only variable that was statistically significantly related. With addition of experience dosing with mL in the model, parent age remained statistically significantly related (AOR=1.04[1.001-1.07]).