Predicting Preeclampsia using sFlt-1:PlGF Ratio in Symptomatic Women

High blood pressurePreeclampsia occurs in 5 to 8% of pregnancies and is a major contributor of premature deliveries and neonatal morbidity in the U.S. and worldwide. It is characterized by new onset hypertension and proteinuria after 20 weeks of gestation and delivery is currently the only treatment. Because the etiology of preeclampsia is poorly understood, our ability to distinguish between different hypertensive disorders of pregnancy remains limited.  In addition, our ability to predict and prevent preeclampsia continues to be poor. We have previously blogged about the use of circulating angiogenic factors such as soluble fms-like tyrosine 1 (sFLT-1) and placental growth factor (PlGF) as early predictors of preeclampsia.

In January 2016 study (funded by Roche Diagnostics), Zeisler, et. al. examined the predictive value of the sFlt-1:PlGF ratio to predict the absence or presence of preeclampsia in women with suspected preeclampsia. The study included two groups of pregnant women with elevated blood pressure and suspected preeclampsia: a development cohort with 500 women (101 had preeclampsia or HELLP syndrome) and a validation cohort with 550 women (98 had preeclampsia).

Using the development cohort, the authors established an sFlt-1:PlGF ratio of 38 as a cutoff for predicting preeclampsia. Using the validation cohort, the authors used the sFlt-1:PlGF ratio of 38 to determine the ability to rule out preeclampsia within 1 week of presenting with symptoms and the ability to rule in preeclampsia within 4 weeks of presenting with symptoms. In the validation cohort, 15 women developed preeclampsia within 1 week (prevalence = 15/550= 2.7%) and the sFlt-1:PlGF ratio of 38 demonstrated a negative predictive value of 99.3% to rule out preeclampsia within one week of presenting with symptoms. In the validation cohort, 71 women developed preeclampsia within 4 weeks (prevalence = 71/550= 13%) and they reported a positive predictive value of 36.7% to predict preeclampsia within 4 weeks.  The authors conclude that an sFlt-1:PlGF ratio of 38 or lower can be used to predict the short term absence of preeclampsia in women who are suspected of having preeclampsia.

I have depicted their data below in a familiar 2×2 format.




Rule out preeclampsia within 1 week

sFlt-1:PlGF ratio

Preeclampsia +

Preeclampsia –







+ PV 9.2%





– PV 99.3%





Sensitivity 80%

Specificity 78%


Rule in preeclampsia within 4 weeks

sFlt-1:PlGF ratio

Preeclampsia +

Preeclampsia –







+ PV 36.7%





– PV 94%





Sensitivity 66%

Specificity 83%


One can conclude that the sFlt-1:PlGF ratio has an excellent negative predictive value to rule out preeclampsia in both 1 week and 4 weeks (99.3 and 94% respectively), but the positive predictive value is poor for both (9.2 and 36.7% respectively). However, one needs to think critically about the data. In both populations, despite the fact that the women have symptoms of preeclampsia, the prevalence of preeclampsia is still low (2.7% within 1 week and 13% within 4 weeks). Therefore, a marker with high positive predictive value is needed.

If we take the data from the within 1 week population in the table above and instead of using the sFlt-1:PlGF ratio, we flip a coin such that we get a sensitivity of 50% and specificity of 50% the negative predictive value is still 97% (see table below). The sFlt-1:PlGF ratio improves the negative predictive value by 3% over the flip of a coin. Why is this? This is because the pretest probability of not developing preeclampsia within one week, in these symptomatic women, is already 97.3%. The sFlt-1:PlGF ratio adds little to the negative predictive value.

Rule out preeclampsia within 1 week

Coin Flip

Preeclampsia +

Preeclampsia –







+ PV  2.7%




– PV 97%





Sensitivity 50%

Specificity 50%


In summary, it is clear that markers with a better positive predictive value are still needed to accurately predict women who are likely to develop preeclampsia even in a population of pregnant women with signs and symptoms.

Cell-free DNA screening tests in the general obstetrical population

DNAIt has been several years since cell-free DNA (cfDNA) tests for the detection of fetal aneuploidies became available. The first clinical studies of these tests were reported in women who, because of age or other reasons, were already at increased risk of having an affected pregnancy (i.e. “high risk” women). While these studies demonstrated the superior performance of cfDNA tests compared to traditional biochemical tests, their application to women at low risk was not encouraged because of lack of evidence regarding how well they would work in that population. A recent report on cfDNA screening tests in the general obstetrical population now provides much needed evidence.

Investigators at Brown University described several clinical utility aspects of cfDNA screening for common aneuploidies through the implementation of a statewide program called DNAFirst that offered cfDNA screening tests to the general pregnancy population in the state of Rhode Island. The clinical utility aspects that were investigated were a comparison of screening uptake rates before and after the DNAFirst program, an evaluation of a reflexive serum testing protocol for cfDNA tests that failed to produce a result, and explored women’s decision-making.

Over 11 months, 2,681 women agreed to undergo screening through 72 providers. Prior to undergoing testing, the women received information about cfDNA testing by primary obstetrical care providers. The median maternal age was 31 years and 79% of the women were younger than 35 years of age. There were 16 positive (i.e. abnormal for trisomy 21, 18, or 13) cfDNA results, 12 of which were confirmed as true positive and 4 of which were false-positive. 2,515 women had a negative screening result and all were true-negatives. 150 tests failed to produce a result (none of which were known to have trisomy). Collectively, these data produced a sensitivity of 100%, a positive predictive value of 75% and a false-positive rate of 0.15%. By comparison, the most effective biochemical screening test (the Integrated test) has a 90% detection rate, a 3% false-positive rate, and a positive predictive value of only 6%.

A small number of women who participated in the study (113) completed a survey asking them about their understanding of cfDNA testing. Women reported receiving information from their care provider in 9 minutes or less. While 85% understood that the test identified Down syndrome, 15% incorrectly thought it identified all genetic problems. 79% understood that a negative result did not rule out Down syndrome but 13% thought it did. These survey results suggest that most women do understand the basic concepts of cfDNA screening.

The study’s authors concluded that cfDNA screening tests perform very well in the general pregnancy population and that women understand the basic concepts of screening. Further, the tests were easily incorporated into routine practices. They encouraged clinical laboratories to offer cfDNA screening tests to improve access to better aneuploidy screening for the more than 2 million pregnant women in the United States who choose to undergo such testing each year.

An Update on Zika Virus Testing in Pregnant Women

We have previously blogged about Zika virus   during pregnancy.That post was in February of 2016 and a lot has changed since then.


For one thing, Zika has been shown to be transmitted via sexual contact from an infected individual (even if he or she does not have symptoms) to a non-infected individual.  The use of condoms can help, and there are guidelines for the pre-conception prevention of sexual transmission. 

In addition, scientists at the CDC have concluded that Zika virus infection does cause microcephaly and other brain defects. This means that women who are infected with Zika virus during pregnancy are at increased risk of having a baby with these problems, but it does not mean that all women with Zika virus infection during pregnancy will have these problems.

Other changes that have occurred since last year include the FDA's Emergency Use Authorization (EUA) for several diagnostic tools for Zika virus, including the Trioplex Real-Time RT-PCR (rRT-PCR) assay and the Zika MAC-ELISA. 

The Trioplex assay is for the detection of RNA from dengue, chikungunya and Zika viruses in serum, whole blood (EDTA), and cerebrospinal fluid (CSF). This is important since dengue and chikungunya are often in the same differential diagnosis with Zika virus. The assay can also be used to detect Zika virus RNA in urine & amniotic fluid.

The Zika MAC-ELISA is intended for the qualitative detection of Zika virus IgM antibodies in human sera or cerebrospinal fluid (CSF).  however, due to cross-reaction with other flaviviruses and possible nonspecific reactivity, results may be difficult to interpret. Consequently, presumed positive, equivocal, or inconclusive tests must be confirmed by plaque-reduction neutralization testing (PRNT).

According to the CDC, who should be tested?

Asymptomatic Pregnant Women

For asymptomatic pregnant women who have traveled to areas with active Zika virus transmission, RNA nucleic acid testing (NAT) testing is recommended on serum and urine within 2 weeks of the date of last possible exposure. Zika virus-specific IgM testing should be performed on women within 2-12 weeks after travel to an area of active transmission or who have had sexual contact with a man confirmed to have Zika virus infection. In areas with active Zika virus transmission, asymptomatic pregnant women should undergo IgM testing as part of routine obstetric care in the 1st and 2nd trimesters. Presumed positive, equivocal, or inconclusive IgM results must be confirmed by plaque reduction neutralization test (PRNT).

Symptomatic Pregnant Women

For symptomatic pregnant women with exposure to Zika virus, RNA nucleic acid testing (NAT) of serum and urine is recommended up to 2 weeks after symptom onset. Whole blood can also be tested for Zika RNA alongside serum and urine. Urine should always be collected with a patient-matched serum specimen. A positive RNA NAT result on any sample confirms Zika virus infection and no additional testing is indicated. A negative RNA NAT result does not exclude Zika virus infection and serum should be tested for the presence of IgM antibodies. If more than 2 weeks have passed since the onset of Zika virus symptoms, specific IgM testing is recommended. Reflex RNA NAT testing should be performed as a subsequent test for pregnant women who are IgM positive.

For recommendations of testing non-pregnant women, and infants, visit the FDA website.

A second hCG blood test that can be performed at the point-of-care

Finger Stick

We have blogged previously about the limitations of urine hCG tests to detect pregnancy in a hospital setting and about the Abbott iSTAT, the first FDA approved device for detection of hCG in whole blood at the point-of-care.

Recently, Nerenz et al evaluated the NOWDiagnostics ADEXUSDx hCG test, a qualitative immunoassay device for the detection of hCG in anticoagulant-free whole blood, heparinized whole blood, or heparinized plasma.  This device is read visually, like the urine/serum POC devices, but it is FDA approved for the use of whole blood samples.


Overall, the device performed very well for the detection of hCG using capillary fingerstick samples.

The device has several limitations.

  1. The ADEXUSDx product is a qualitative, not quantitative device. This is different than the iSTAT device, that we reported on previously, as the iSTAT is quantitative with a range of 5-2000 IU/L. However, since hCG concentrations in women rise so rapidly in early pregnancy, and with such a narrow dynamic range some would argue that the iSTAT device is almost a qualitative device.
  2. The authors reported that the device recognized 100% of samples at a concentration of 27 IU/L and approximately 50% of samples at a concentration around 10 IU/L. This analytical sensitivity is similar to the POC serum devices currently used in hospitals.
  3. Finally, the ADEXUSDx device showed susceptibility to the high-dose hook effect, as decreasing test line intensity was observed at concentrations ≥600,000 IU/L, but all devices were interpreted as positive. This limitation is similar to that seen with the iSTAT device.

Overall, this is a nice addition to the available POC hCG devices currently on the market. It should be pointed out that the Abbott iSTAT and the NOWDiagnostics ADEXUSDx are the only two devices currently available for the diagnosis of pregnancy using whole blood at the point of care.

Whole blood should not be used on devices that are only FDA approved for urine and/or serum, as we have pointed out in previous publications.  

Placental Alpha-Microglobulin-1 as a Marker of Membrane Rupture

Preterm babyPremature rupture of membranes (PROM) is spontaneous rupture of fetal membranes before the onset of uterine contractions. Preterm PROM, which is PROM before 37 weeks is a major cause of preterm birth.

Previously, we have blogged about the cervicovaginal markers IGFBP1 and AFP to diagnose PROM. In recent years, a number of studies have reported on the utility of cervicovaginal placental alpha-microglobulin-1 (PAMG-1) as a marker of Rupture of Membranes.

PAMG-1 is present in blood, amniotic fluid (AF), and cervicovaginal fluid of pregnant women. The concentration of PAMG-1 in AF (2,000–25,000 ng/mL) is several thousand times higher than that in cervico-vaginal discharge when the fetal membranes are intact (0.05–0.2 ng/mL). The high concentration of PAMG-1 in AF makes it potentially a good marker to detect the presence of AF in the vaginal canal.

In one of the largest studies, Lee et al examined 184 women with symptoms or signs of PROM. 159 were later confirmed to have PROM. In this population, PAMG-1 demonstrated a sensitivity of 98.7%, specificity of 87.5%, positive predictive value of 98%, and a negative predictive value of 91.3%. In contrast, Nitrazine in the same patients demonstrated a sensitivity of 88.1%, specificity of 87.5%, positive predictive value of 97.9%, and a negative predictive value of 52.5%. This performance is supported by several other studies as well.

Diagnostic Utility of PAMG-1







Lee et al. 2007 Obstet Gynecol






Cousins et al.2005 Am J Perinatol






Ng et al. 2013 BioMed Res Intern






Abdelazim et al. 2013 J Obstet Gyneacol Res





In summary, PAMG-1 appears to be a viable method to detect PROM in cervicovaginal fluid and appears to be superior to conventional methods.

Zika Virus Testing in Pregnant Women

Zika Figure croppedZika virus is a mosquito borne illness that is found in South and Central America. The most common symptoms include fever, rash, joint pain, and conjunctivitis (red eyes). The virus is spread by mosquitos primarily in the Aedes aegypti and Aedes albopictus species which also carry other tropical diseases such as Chikungunya and Dengue. These mosquitos bite humans primarily in the daytime. It is estimated that 80% of people infected with the Zika virus are asymptomatic. In most people with symptoms, the illness is self-limited and resolves in 5-7 days. Disease requiring hospitalization is rare.

Recently, there have been reports in Brazil of an increased rate of microcephaly and other poor pregnancy outcomes in babies from women who were infected with the Zika virus while pregnant.  However, further studies are needed to understand the relationship between these outcomes and infection. In the meantime, the Centers for Disease Control and Prevention (CDC) have issued special travel precautions for pregnant women and women trying to get pregnant.

So who should be tested for Zika virus and what testing is available?

Initially, the CDC advised that a pregnant woman should only be tested if she has symptoms of Zika virus within the first week of being in an endemic area. If the mother is positive, then the infant should be tested for congenital infection.

However, very recently, the CDC updated the guidelines to include asymptomatic pregnant women who live in or have traveled to endemic areas.  The update recommends that serologic testing be offered to pregnant women can be offered testing within 2-12 weeks after they return from travel. For asymptomatic pregnant women who live in endemic areas, testing is recommended at the initiation of prenatal care with follow-up testing mid-second trimester.

For infants that have microcephaly or intracranial calcifications detected prenatally or at birth with a mother who was potentially infected with Zika virus during pregnancy, the infant should be tested. If infants have positive or inconclusive test findings, the case should be reported to the State or local health department for follow-up. If the infant tests negative, other possible etiologies for the microcephaly should be investigated.

For infants without microcephaly or intracranial calcifications with a mother who was potentially infected with Zika virus during pregnancy, subsequent evaluation depends on the mother's results. If the mother test's negative, no further testing is required. If the mother received positive or intermediate results, then the infant should be tested. If the infant test's negative, then no further testing is required. If the infant test's positive then further clinical evaluation (including comprehensive physical exam, cranial ultrasound and ophthalmologic evaluation) should be performed and the infant should be followed for long term sequelae.

No commercial tests are yet available for Zika virus. Testing is performed at the CDC and some local health departments. The tests currently performed include RT-PCR, ELISA for IgM and a plaque reduction neutralization test (PRNT).

Infants who are being evaluated should have RT-PCR performed on serum (from infant or umbilical cord) within 2 days of birth. CSF if available should also be tested by RT-PCR. ELISA for IgM should be performed on infant serum and CSF.

Mothers being evaluated should have serum tested using ELISA. RT-PCR can be performed during the first week of viral infection. Amniocentesis should be offered to pregnant women who test positive or indeterminate and RT-PCR should be performed on the amniotic fluid.

Note that false positives can occur in the ELISA assay due to cross reactivity with other related flaviviruses such as dengue or yellow fever. PRNT can be used to distinguish false positives from true positive results. If neutralizing antibody titers are ≥ 4-fold greater than dengue virus neutralizing antibody titers, then Zika virus is considered positive. Immunohistochemistry can also be performed on fixed placenta or umbilical cord tissue. If any of any of the tests are positive, the infant is considered congenitally infected.

Currently, there is no anti-viral treatment or vaccination for Zika virus. Treatment is supportive. The best defense against Zika is preventing maternal infection by avoiding mosquito bites. It is important to note that, when used as instructed, insect repellants containing DEET, picardin, and IR3535 are safe for pregnant women.

How Early Can Pregnancy Be Detected?

Calendar_2“How early can pregnancy be detected?” is a question we are asked all the time. The short answer is, “It depends.” Let’s answer this question one step at a time.

First, the most common way to detect early pregnancy is by measuring the hormone human chorionic gonadotropin (hCG). If an egg is fertilized, the developing embryo will attach to the lining of the uterus around 6-12 days after ovulation. This is called implantation.  The hormone hCG is produced by trophoblastic cells (the outer layer of the embryo) after implantation. It takes several days for hCG to be detectable in blood or urine. hCG production increases very rapidly with serum concentrations doubling every 1-1.5 days in the first 8-10 weeks of pregnancy. So, detecting pregnancy first depends on how quickly implantation occurs.

Second, it depends on the sample in which hCG is measured; blood or urine. Urine concentrations of hCG are almost always lower than serum concentrations. In addition, urine concentrations of hCG can be affected by fluid intake. If large amounts of fluids are ingested (think Big Gulp)  then urine concentrations will be more dilute. This is why first morning urine samples are often recommended because this urine is usually the most concentrated of the day since people don’t tend to drink anything during the sleeping hours. The amount of water in blood is more regulated that that of urine and generally does not change, even after ingesting large amounts of liquid. Therefore, use of a blood sample will generally detect pregnancy earlier than use of urine. 

Third, it depends on the method used to detect hCG; qualitative or quantitative. Qualitative devices are those that can be purchased over-the-counter to detect hCG in urine. They are also used in hospitals and doctor offices. These devices generally have cutoffs for positivity that vary from about 20-50 IU/L. The cutoff varies widely by brand. Interestingly, we have shown that the devices used at home are often more sensitive than the devices used in the hospital!!  We have previously blogged about this topic. Quantitative hCG assays are performed using blood samples in laboratories and are much more analytically sensitive than qualitative assays. Most quantitative hCG assays can detect hCG at concentrations of 2 IU/L and some can go as low as 0.1 IU/L. Therefore, quantitative assays will be able to detect pregnancy earlier than qualitative assays.

Fourth, when the clinical sensitivity of an hCG test for diagnosing pregnancy is determined, it is usually determined as a function of the number of days relative to the expected day of the menstrual period (EMP). How early an hCG test can detect pregnancy depends on how the EMP is estimated. Most women estimate EMP by counting 28 days from the first day of the last menstrual period (LMP). This 28-day cycle includes the approximate 14 days between first day of menses and ovulation (called the follicular phase) and the approximate 14 days between ovulation and the day before the next menstrual period (called the luteal phase). However, the length of menstrual periods varies between women. Studies have shown that most of the variation occurs in the follicular phase.Therefore, the most accurate way to estimate the EMP is by measuring 14 days from ovulation as estimated by detecting a dramatic rise in the concentration of luteinizing hormone (LH), commonly referred to as the LH surge. Using 14 days from the LH surge can detect 100% of pregnancies by the EMP, as opposed to using 28 days from LMP which did not detect 100% of pregnancies until 7 days after EMP.  By measuring serum hCG, 100% of pregnancies can be detected by EMP and nearly all pregnancies can be  detected by 3 days before EMP. 

In summary, how early pregnancy can be detected depends on many factors. In some cases pregnancy can be detected more than 3 days before EMP. Virtually all pregnancies should be detected by one week after EMP.

“Should I freeze my eggs?”

Ovary with eggs"A question some women face: when to freeze their eggs." This was the start of a news piece I heard on NPR as I drove to work this morning. It caught my attention and I realized we haven't spent much time on this blog exploring the tests used to help achieve pregnancy.

The premise of "ovarian reserve" testing is rather straightforward: they are supposed to help a woman concerned about fertility decide whether she should freeze her eggs for future use or if she can wait to conceive because time is still on her side.

Unlike sperm, which are produced continually over a man's reproductive lifetime, the number of eggs in the female ovaries peaks during fetal development, declines over time, and do not regenerate. Thus, female fertility declines with each year of life. Tests of ovarian reserve are supposed to reflect the number and quality of remaining eggs, a key element in reproductive potential. Ovarian reserve tests include both blood tests and ultrasound tests. This post will focus on the blood tests.


With normal ovarian function, the developing eggs in the ovary secrete hormones which keep the concentration of follicle-stimulating hormone (FSH) in its normal range during the first few days of the menstrual cycle. When the number of developing eggs is decreased, the concentration of FSH is increased. Thus, measuring FSH on day 3 of the menstrual cycle is a test of ovarian reserve and higher values are associated with lower fertility.


Estradiol is released from developing eggs during the first few days of the menstrual cycle. Estradiol concentrations are usually low during days 2-4 but increase thereafter. A high value at this time suggests poor ovarian reserve.


Anti-Müllerian hormone (AMH) is produced by the granulosa cells of eggs and so its concentration reflects the size of the ovarian pool of eggs. As the number of eggs declines, so too does AMH. But while the concentration of AMH predicts the quantity of eggs, it does not predict their quality.

Inhibin B

Inhibin B is another hormone released by eggs and so it is similar to AMH in evaluating the number of eggs in the ovary. Because inhibin B helps to regulate FSH concentrations, a low inhibin B is associated with a high FSH. Unlike AMH, inhibin B shows a lot of variation across menstrual cycles so it's not a recommended test of ovarian reserve.

Clomiphene Citrate Challenge Test

Clomiphene is a selective estrogen receptor modulator that causes the pituitary gland to release the hormones needed to stimulate ovulation. This test is performed by measuring FSH on cycle day 3 (before giving Clomiphene) and again on day 10 (after giving Clomiphene, daily, on days 5-9). In women with normal ovarian reserve, the rising inhibin B and estradiol concentrations produced from the developing eggs would suppress FSH. However, in women with decreased ovarian reserve, FSH is elevated on day 10 due to the lower concentrations of inhibin B and estradiol.

Not surprisingly, no single test is adequate to evaluate a woman's ovarian reserve. To address that, it is not unusual for doctors to perform several of these tests in an effort to provide a more definitive answer. Unfortunately, there is still no universally agreed upon definition of "decreased ovarian reserve" and evidence of decreased reserve (biochemical or otherwise) does not correlate very well with the inability to conceive.

So while there is a very strong desire to have definitive tests to predict a woman's fertility potential in an effort to help her decide if she can wait to conceive or take action such as harvesting and freezing eggs for future use, such answers are not yet available from lab tests alone.

Personalized medicine during pregnancy

Pregnancy dnaPersonalized medicine can be defined as customized disease prevention therapies and drug treatment protocols based on knowledge of an individual’s unique genetic makeup, metabolic profile and clinical presentation. So far, personalized medicine has focused on the prevention and treatment of conditions affecting adults such as cancer and cardiovascular disease.  However pregnancy is a unique situation where the unique characteristics of two individuals are being assessed: mother and infant. Remarkably few studies have addressed the therapeutic implications of recent advances in genetic technologies for the fetus. Focus has been more on prenatal diagnosis than on fetal treatment. As molecular technologies advance and costs decrease, targeted genetic testing and even whole genome sequencing of the fetus are likely to become more available. This brings with it a number of ethical issues especially as it relates to testing of the infant. For instance, there are questions of informed consent, confidentiality of results, the clinical significance of genetic polymorphisms and decisions to terminate pregnancy on the basis of these test results.

Nonetheless, there have been some interesting advances in personalized medicine, for both mother and fetus, during pregnancy. This is the focus of an upcoming symposium at the AACC meeting to be held tomorrow, July 29th, at 10:30 am in Atlanta, Georgia.  

Predicting Response to Drugs:  Sixty-four percent of women in the US are prescribed more than one drug during pregnancy (excluding vitamins). A better understanding of how drugs are metabolized during pregnancy and how they affect the fetus is clearly needed. Cytochrome P450 is the predominant class of oxidative enzymes that catalyze many types of drugs. Interestingly, the expression of a number of P450 genes is altered during pregnancy. Most notably, CYP1A2 has been shown to be decreased by 65% by the 3rd trimester. In the past several years, several studies have examined the ability to predict a woman’s response to drugs used during pregnancy, like tocolytics and anti-emetics, based on their genotype. A study by Haas, et. al. demonstrated that CYP3A5 high-expressing women had lower circulating concentrations of Nifedipine, a common tocolytic. A study by Lehmann, et. al. demonstrated that a genotype for serotonin receptor subunits 5-HT3A and 5-HT3B may play a role in hyperemesis severity and response to anti-emetics. This type of genotyping is not yet ready for prime time, but it holds promise for better utilization of medications during pregnancy.

Assessing the Fetus: We have blogged previously about cell free fetal DNA (cffDNA) in maternal blood and its utility in predicting fetal trisomy. cffDNA can also be used to assess fetal Rhesus D (RhD) status. This method can be used to determine the fetal RhD genotype when the mother has clinically significant alloantibody to the D antigen AND the father is heterozygous for RhD or is not available for testing. Testing such as this is useful because instead of treating all RhD-negative women with RhD immunoglobulin, treatment can be targeted to mothers that carry RhD-positive fetuses. This type of approach can conserve supplies of therapeutic anti-D, prevent unnecessary administration of a human-derived blood product to a vulnerable patient group, and avoid subjecting RhD-positive infants to intensive antenatal monitoring to predict and treat fetal anemia. Interestingly, despite the fact that the American College of Obstetricians and Gynecologists support the use of cffDNA for RhD assessment, it is not a widely used clinical tool in the United States.

Predicting Viability: Not all personalized medicine is genetic. Personalized medicine can also be used to guide treatments. With this in mind, there are several publications that suggest novel uses for hCG testing. The first takes advantage of “semi-quantitative” urine hCG devices. These devices are similar to home pregnancy devices, but they essentially contain multiple detection strips with different cutoffs that can give the reader a rough estimate of the urine hCG concentration (>25, >100, >500, >2000 or >10,000). Several studies have examined the use of these devices in a home setting following medical abortion as a replacement for clinic follow-up. If the woman is able to demonstrate decreasing hCG concentrations at home, she can avoid a return visit to the clinic. This can reduce the burden on the healthcare setting, but it could also help women for whom getting to a clinic is difficult because of work or family commitments or who live in a remote geography. Both studies demonstrate that use of semi-quantitative hCG devices in this setting had 100% sensitivity to detect unsuccessful abortions. The second interesting use for hCG measurement is in the prediction of fetal viability. Several studies have suggested that urine and serum concentrations of hyperglycosylated hCG (hCG-H) are low in women with pregnancy failure. These studies suggest that measurements of serum or urine hCG-H to detect failed pregnancy is 60-70% sensitive and 97-100% specific (links here and here). These studies are small and there is not currently a readily accessible assay for hCG-H, but it is intriguing to think about the possibility of a test that could distinguish viable from non-viable pregnancies especially in an emergency setting when physicians are making treatment decisions and have to take into account potential risks to the fetus.

Can a personalized approach improve IVF success rates?

Test Tube Baby

This post was written by Robert D. Nerenz, PhD, an assistant professor of pathology and laboratory medicine at the University of Kentucky, in Lexington.

In the United States, an estimated one in seven couples experience infertility and for many of these couples, in vitro fertilization (IVF) represents their best chance of achieving pregnancy. However, IVF cycles constitute a significant expense (approximately $12,500 per cycle), disrupt patients’ daily lives and only result in a healthy, live birth 30% of the time! Furthermore, the majority of IVF cycles performed in the United States involve the transfer of multiple embryos. This is of particular concern because multiple embryo transfer carries a finite risk of a multiple gestation pregnancy. Bringing multiple infants to term is associated with an increased risk of poor fetal and maternal outcomes including decreased birth weight, increased rate of fetal death, preeclampsia, gestational diabetes and preterm labor. Clearly, there is a significant need to improve IVF success rates while also minimizing the likelihood of multiple gestation pregnancies.

One strategy that may accomplish both of these goals is to perform “single embryo transfer” by implanting one embryo that has a high likelihood of producing pregnancy and, ultimately, a live birth. This is the focus of an upcoming symposium at the AACC meeting to be held July 29th at 10:30 am in Atlanta, Georgia. Fertility clinics around the world currently attempt to do this by observing embryos under a microscope and choosing the best embryo on the basis of its physical appearance. Unfortunately, this approach does not provide any information about the embryo’s genetic status. This is an important limitation because aneuploidy (the gain or loss of a chromosome) is the most common cause of pregnancy loss. It is also estimated to occur in ≥10% of clinical pregnancies and becomes more frequent with increasing maternal age.

To ensure that aneuploid embryos are not selected for transfer, several research groups have developed methods collectively known as comprehensive chromosome screening (CCS). CCS involves culturing embryos for 5-6 days, removing a few cells from the trophectoderm (the outer cell layer that develops into the placenta), isolating the DNA from those cells and assessing the copy number of each chromosome using techniques such as quantitative PCR, comparative genomic hybridization, or single nucleotide polymorphism arrays. Following determination of the embryos’ genetic status, only embryos with the normal number of chromosomes are chosen for transfer. In multiple prospective, randomized controlled trials described here and here, CCS has been shown to increase the pregnancy rate and decrease the frequency of multiple gestation pregnancies. As a result, CCS is beginning to make the transition from the research setting to use with patients.

The ability to transfer only euploid embryos represents the most promising application of novel technologies to IVF but ongoing research is focused on other ways to improve the IVF success rate. Many different groups are analyzing the culture medium that embryos are grown in prior to implantation. It is hoped that this will provide information about the embryos’ metabolic health and might help identify which embryos are most likely to result in pregnancy and live birth. Other groups are evaluating endometrial gene expression profiles to assess endometrial receptivity and ultimately determine the best time to perform embryo transfer. While both of these approaches have technical limitations and are not quite ready for primetime, they have the potential to greatly improve our current standard of care and may be ready for clinical use in the near future.