Aspirin nonadherence renders pre-eclampsia prevention ineffective

Adequate aspirin adherence in the prevention of pre-eclampsia should be exercised if outcomes are to be improved for high-risk women and their babies, according to a recent study.

“Aspirin plays an effective role in the prevention of pre-eclampsia among high-risk women with adherence of ≥90 percent. However, the prevalence of inadequate adherence of aspirin is high and is associated with a significantly higher incidence of pre-eclampsia, intrauterine growth restriction (IUGR) and preterm delivery,” the investigators said.

In the current study, the investigators looked at 187 pregnant women (mean age, 32 years) at high risk of pre-eclampsia, among whom 145 were prescribed aspirin based on centre-specific practice (72 percent at 100 mg; 28 percent at 150 mg). None of the women were aspirin-resistant.

More than half of the sample (56 percent) were found to be adherent to treatment based on quantitative assessment, while 44 percent demonstrated inadequate adherence (defined as normal platelet function analyser [PFA] 100 and nondetectable plasma salicylic acid [SA] in <90 percent of time points). Those who were adherent were more likely to have achieved secondary-level education only (p=0.005) and less likely to have previous pre-eclampsia. [Hypertension 2020;75:1125-1132]

On logistic regression analysis, inadequate adherence was associated with a higher incidence of early-onset (17 percent vs 2 percent; odds ratio [OR], 1.9, 95 percent confidence interval [CI], 1.1–8.7; p=0.04) and late-onset pre-eclampsia (41 percent vs 5 percent; OR, 4.2, 95 percent CI, 1.4–19.8; p=0.04), IUGR (29 percent vs 5 percent; OR, 5.8, 95 percent CI, 1.2–8.3; p=0.001), preterm delivery (27 percent vs 10 percent; OR, 5.2, 95 percent CI, 1.5–8.7; p=0.008), as well as an increase in antihypertensive requirements in pregnancy (60 percent vs 10 percent; OR, 4.6, 95 percent CI, 1.2–10.5; p=0.003).

Kaplan-Meier analysis confirmed a lower incidence of premature delivery in the group of women who were ≥90-percent adherent (hazard ratio, 0.3, 95 percent CI, 0.2–0.5; p<0.001).

Kappa coefficient agreement between quantitative assessment and self-reported aspirin adherence was only moderate (κ=0.48; p<0.0001).

“Our data also showed that a graded adherence did not affect clinical outcome. This is in keeping with current data that the prophylactic benefit of aspirin is most evident in women who are ≥90-percent adherent with aspirin,” the investigators said. [Am J Obstet Gynecol 2017;217:685.e1–685.e5]

“Therefore, suggesting adequate adherence with aspirin is essential and that nonadherence … among high-risk pregnant women may result in preventable obstetric complications,” they added.

The investigators, however, pointed out that self-reported adherence is an unreliable method of assessment and a clinically available quantitative method should assist in monitoring adherence. The present study utilized a commercialized, clinically available PFA-100 assay and laboratory-based plasma SA detection with a sensitive liquid chromatography tandem-mass spectrometry method.

Use of PFA-100 alone may be adequate within its limitations for quantitative assessment of adherence to aspirin, they added. “This test is also readily available with a reasonable turnaround time in most institutions and may serve as a role for pragmatically assessing adherence in clinical practice.”

Additional investigation on the cost-effectiveness on routine PFA-100 use for adherence assessment should be beneficial, the investigators said.