Oral Presentation Society of Obstetric Medicine of Australia and New Zealand ASM 2018

A cohort study utilising biochemical assessment of aspirin compliance vs resistance in high-risk pregnant women. (#21)

Renuka Dr Shanmugalingam 1 2 3 , Xiao Suo Dr Wang 4 , Katrina Dr Chau 3 5 , Bei Dr Xu 3 , Gaksoo Ms Lee 2 , Roshika Ms Kumar 2 , Annemarie Prof Hennessy 1 2 3 , Angela Prof Makris 1 2 3
  1. School of Medicine, Western Sydney University, Sydney, NSW, Australia
  2. Renal Medicine, South Western Sydney Local Health District, Liverpool, NSW, Australia
  3. Vascular Immunology, Heart Research Institue, Newtown, NSW, Australia
  4. Bosch Mass Spectrometry Facility, Bosch Institute, Sydney Medical School, University of Sydney, Newtown, NSW, Australia
  5. School of Medicine, University of Sydney, SYDNEY, NSW, Australia

Introduction

The benefit of low-dose aspirin in preventing preeclampsia is well established. Despite prescription of aspirin, 30-40% of women still develop preeclampsia. Aspirin-resistance or non-compliance, and their effects on clinical outcomes has not been examined in high-risk pregnant women and could, in-part, explain the observed lack of clinical response.

Objective/Hypothesis

We aimed to examine the incidence of aspirin non-compliance and resistance through biochemical analysis and compare this against self-reported compliance. We also examined clinical outcomes against biochemical compliance.

 

Methods

Sequential recruitment of women in a high-risk pregnancy clinic was undertaken in a metropolitan hospital. Demographic and clinical data of women together with a 3-point questionnaire and plasma collection was undertaken at 8 time-points (12,16,20,24,28,32,36,38 weeks gestation). Blood samples were assessed for PFA 100 (platelet function analyser) and plasma salicylate acid (SA) detection through liquid-chromatography, mass-spectrometry (LCMS). Non-compliance was defined as normal PFA100 and non-detectable plasma SA in <90% timepoints. Resistance was defined as a normal PFA100 but detectable plasma SA. Clinical outcomes were compared between compliant and non-compliant women prescribed aspirin <16 weeks of gestation. Statistical analysis utilised chi-squared analysis and linear regression utilising SPSSv24 and significance was set at p<0.05.

Results

Seventy-one women completed the protocol. Biochemical non-compliance was identified in 22(31%) women and only 45(63%) of women’s self-reported compliance corresponded biochemically (kappa coefficient=0.65)). No women were aspirin resistant. The clinical outcomes of compliance and non-compliance with aspirin were significantly different. Compliant women had a lower incidence of late-onset preeclampsia (4.1% vs 59% %,p<0.001), lower blood pressure (p=0.01) and were more than 34 weeks of gestation at delivery (96% vs 81%,p=0.02). Furthermore, the incidence of early-onset preeclampsia (2% vs 18%, p=0.001) and IUGR was lower (4.1% vs 23% p=0.003), favouring > 90% compliance.

Conclusion

Aspirin non-compliance is more likely than aspirin resistance and self-reporting is not a reliable measure. Women who are non-compliant have worse clinical outcomes.