Perceived, objective, and applied numeracy among pregnant women engaged in home blood pressure monitoring in Ghana

Background

Hypertensive disorders of pregnancy are associated with poor maternal and neonatal outcomes. Since elevated blood pressure is often a first presenting sign, a major function of antenatal care is frequent blood pressure monitoring. A newer approach to this—patient-performed home monitoring—has not been widely implemented in low- and middle-income countries, including Ghana. Patient numeracy levels that are sufficient to understand and interpret home blood pressure values are a critical component of a successful home monitoring intervention.

Objective

To evaluate perceived, objective, and applied numeracy to identify elevated blood pressure values among pregnant women engaged in home blood pressure monitoring in Ghana.

Study Design

Participants were 80 pregnant women at a tertiary hospital in Accra, Ghana. After training, participants engaged in home blood pressure monitoring for 2 to 4 weeks. A post-monitoring survey evaluated confidence and experience interpreting blood pressure values, a validated numeracy scale, and interpretation of blood pressure monitor outputs—half with numbers only and half with both numbers and colors. Mean correct responses on numbers only and numbers and colors outputs were compared. Linear regression evaluated predictors of correct interpretation of blood pressures.

Results

On a validated numeracy scale, mean score was 16.73 (SD: 6.01) out of 25, with 73.8% (n=59) having numeracy. Perceived ability was high, with 70.9% (n=56) definitely believing they could interpret blood pressures values. However, on objective evaluation, only 36.3% (n=29) correctly identified the cutoff for elevated systolic and 26.3% (n=21) for elevated diastolic blood pressure values. Out of eight displayed blood pressure monitor outputs, correct identification was significantly higher on outputs with both numbers and colors (μ=7.19, σ=0.81) compared to numbers only (μ=6.54, σ=1.35). On an adjusted linear regression, only scores on the numeracy scale had a significant yet small association with correctly identifying blood pressure monitor outputs (β 0.07, P=.025).

Conclusion

Home blood pressure monitoring would benefit from monitors with both numerical and color-coded output. Focused training, rather than education level or general numeracy, may best predict blood pressure interpretation.