Unit of measurement used and parent medication dosing errors

Abstract

Background and objectives: Adopting the milliliter as the preferred unit of measurement has been suggested as a strategy to improve the clarity of medication instructions; teaspoon and tablespoon units may inadvertently endorse nonstandard kitchen spoon use. We examined the association between unit used and parent medication errors and whether nonstandard instruments mediate this relationship.

Methods: Cross-sectional analysis of baseline data from a larger study of provider communication and medication errors. English- or Spanish-speaking parents (n = 287) whose children were prescribed liquid medications in 2 emergency departments were enrolled. Medication error defined as: error in knowledge of prescribed dose, error in observed dose measurement (compared to intended or prescribed dose); >20% deviation threshold for error. Multiple logistic regression performed adjusting for parent age, language, country, race/ethnicity, socioeconomic status, education, health literacy (Short Test of Functional Health Literacy in Adults); child age, chronic disease; site.

Results: Medication errors were common: 39.4% of parents made an error in measurement of the intended dose, 41.1% made an error in the prescribed dose. Furthermore, 16.7% used a nonstandard instrument. Compared with parents who used milliliter-only, parents who used teaspoon or tablespoon units had twice the odds of making an error with the intended (42.5% vs 27.6%, P = .02; adjusted odds ratio=2.3; 95% confidence interval, 1.2-4.4) and prescribed (45.1% vs 31.4%, P = .04; adjusted odds ratio=1.9; 95% confidence interval, 1.03-3.5) dose; associations greater for parents with low health literacy and non-English speakers. Nonstandard instrument use partially mediated teaspoon and tablespoon-associated measurement errors.

Conclusions: Findings support a milliliter-only standard to reduce medication errors.

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

FIGURE 1

Path analysis: Use of nonstandard dosing instrument as a mediator of teaspoon or tablespoon unit–associated errors in measurement compared with the intended (A) and prescribed (B) dose.^{a a}Baron and Kenny criteria for mediation met: teaspoon or tablespoon use associated with measurement error in analyses without nonstandard instrument in model, teaspoon or tablespoon use associated with use of nonstandard instrument, nonstandard instrument associated with errors, and teaspoon or tablespoon no longer significantly associated with error after adjustment for nonstandard instrument. ^bTeaspoon or tablespoon units used alone or in combination. ^cMultiple logistic regression analysis adjusting for parent age, race/ethnicity, language, country of birth, socioeconomic status, education, and HL; child age and child chronic disease; and site. ^dMultiple logistic regression analysis with nonstandard instrument included in the model and adjusting for variables listed in footnote c.