Lower diagnostic threshold for hypertension improves recognition of preeclampsia
The 2017 American College of Cardiology/American Heart Association guidelines for hypertension identified more patients at risk for preeclampsia than the American College of Obstetricians and Gynecologists’ definition, researchers found.
ACOG defines hypertension as BP of 140/90 mm Hg or higher and severe hypertension as BP of 160/110 mm Hg or higher, Natalie A. Bello, MD, MPH, a multimodality imaging cardiologist at the Columbia University Medical Center, told Healio Primary Care.
References:
Chobanian AV, et al. JAMA. 2003;doi:10.1001/jama.289.19.2560.
Vidaeff A, et al. Obstet Gynecol. 2019;doi:10.1097/AOG.0000000000003020.
Whelton PK, et al. Hypertension. 2018;doi:10.1161/HYP.0000000000000065.
“In 2017, the ACC/AHA recommended lowering the diagnostic threshold for stage 1 hypertension to 130/80 mm Hg,” she said. “This is considered prehypertension by ACOG.”
To compare how effectively the ACC/AHA guidelines and ACOG definition identify pregnant patients at risk for preeclampsia or eclampsia, Bello and colleagues conducted a retrospective cohort study of 137,389 pregnant patients (mean age at time of delivery, 30.1 years; 51.6% Hispanic) who delivered singleton infants. The researchers used electronic health record data to calculate net reclassification indices and compare the ACC/AHA diagnostic threshold with the ACOG diagnostic threshold. The study’s primary endpoints were the development of preeclampsia or eclampsia and a composite of preterm birth, small for gestational age and neonatal ICU admission.
The prevalence of chronic hypertension was 14.3% when applying the ACC/AHA criteria vs. 4.3% with ACOG criteria, the researchers reported. Meanwhile, the prevalence of gestational hypertension was 13.8% with ACC/AHA criteria vs. 6% with ACOG criteria. Applying the ACC/AHA criteria resulted in a 17.8% absolute increase in the overall prevalence of hypertension, from 10.3% to 28.1%, according to the researchers.
“We found that women who were classified with gestational hypertension using the ACOG criteria who met diagnostic threshold for chronic hypertension using ACC/AHA criteria were at the highest risk of developing preeclampsia or eclampsia,” Bello said.
Among these patients, there was an adjusted risk ratio of 13.58 (95% CI, 12.49-14.77) for developing preeclampsia. Overall, the researchers reported that the ACC/AHA criteria was associated with a 20.8% improvement in identifying preeclampsia/eclampsia risk, as well as a 3.8% improvement in identifying fetal and neonatal risks.
“Using a lower threshold may reclassify women at risk and potentially identify those who could benefit from low-dose aspirin for preeclampsia prophylaxis,” Bello said. “But future prospective studies are needed to test this hypothesis.”
Perspective
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I have a great appreciation for the work of this group on this important topic. This is an important contribution to the literature on this topic that is of prime importance to ACOG and obstetricians in the U.S., given how much of a contributor hypertension is to maternal morbidity and mortality.
The important nuance that I am not sure this article accounts for is that the ACOG definition of chronic hypertension does not use any BP criteria, but rather is “hypertension diagnosed or present before pregnancy or before 20 weeks of gestation.” Thus, someone diagnosed with hypertension before pregnancy based on the 2017 ACC/AHA criteria of 130/80 mm Hg would be diagnosed, by ACOG criteria, as a chronic hypertensive. The Practice Bulletin document acknowledges that by saying “obstetric care providers may see an increase in patients classified as hypertensive based on these ACC/AHA definitions.” So, in some ways the paper may show support for how the definition of chronic hypertension is worded by ACOG.
The ACOG definition of hypertension in pregnancy does use criteria that are higher than the ACC/AHA cutoffs and thus the criteria for preeclampsia and gestational hypertension are higher. This paper points out that we need continued research on this topic, especially as there might be important impacts on maternal and birth outcomes.
However, it does warrant some caution that more diagnoses do not automatically result in better clinical outcomes. They certainly result in more intervention, such as medications, testing and changes in approach to birth timing, but that is not always better. A recent randomized controlled trial comparing two different and common approaches to diagnosis of gestational diabetes demonstrates this. While one screening approach was able to diagnose a higher rate of gestational diabetes, there were no differences between the groups in the risks of perinatal and maternal complications. So, it is not always clear that a more liberal diagnostic criterion actually improves outcomes. This is why we need to proceed cautiously with major changes like this.
ACOG will take this article into account, along with all of the other research that is coming out, when considering its definitions. ACOG relies on continued evaluation of the literature to inform their recommendations and guidelines.
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