Cell-free fetal DNA testing for fetal aneuploidy and beyond: clinical integration challenges in the US context

Comparing the Introduction and Implementation of Noninvasive Prenatal Testing (NIPT) in Japan, the Netherlands, and the United States: An Integrative Review

Previous studies suggest that NIPT's implementation differed widely across countries but offer limited insight into what shaped these differences. To address this gap, we conducted an in-depth analysis of how NIPT was incorporated into prenatal care in the US, the Netherlands, and Japan-countries with similar economic status-to identify actionable lessons. We conducted an integrative literature review on the process of introducing and implementing NIPT, stakeholders' roles, documented considerations in the decision to introduce NIPT, implementation choices, and NIPT uptake. We included 184 sources, including white and gray literature and non-English sources. We identified 17 considerations that were documented to have influenced the decision whether to introduce NIPT across five domains: clinical considerations, ethical considerations and societal values, financial considerations, demand and capacity and applicable oversight. Fewer factors seem to have been considered in the US as compared to Japan or the Netherlands. Countries subsequently made choices on how to implement NIPT-we identified 35 such choices. While most of the identified choices were eventually considered by all three countries, they made different decisions (e.g., on out-of-pocket costs). In 2022, the estimated proportion of pregnant persons who used NIPT was 58% in the Netherlands, 49% in the US, and 9% in Japan. While differences in cultural values, population characteristics, and healthcare systems explain some variation, we identified other more adaptable aspects of the decision-making process (e.g., oversight) that may be useful for countries introducing NIPT or similar technologies to consider.

The Emergence and Global Spread of Noninvasive Prenatal Testing

Since its introduction in 2011, noninvasive prenatal testing (NIPT) has spread rapidly around the world. It carries numerous benefits but also raises challenges, often related to sociocultural, legal, and economic contexts. This article describes the implementation of NIPT in nine countries, each with its own unique characteristics: Australia, Canada, China and Hong Kong, India, Israel, Lebanon, the Netherlands, the United Kingdom, and the United States. Themes covered for each country include the structure of the healthcare system, how NIPT is offered, counseling needs and resources, and cultural and legal context regarding disability and pregnancytermination. Some common issues emerge, including cost as a barrier to equitable access, the complexity of decision-making about public funding, and a shortage of appropriate resources that promote informed choice. Conversely, sociocultural values that underlie the use of NIPT vary greatly among countries. The issues described will become even more challenging as NIPT evolves from a second-tier to a first-tier screening test with expanded use.

Genotyping of STR and DIP-STR Markers in Plasma Cell-Free DNA for Simple and Rapid Noninvasive Prenatal Diagnosis of Zygosity of Twin Pregnancies

Due to the high rate of complications, special medical care must be provided especially for monozygotic twin pregnancies, which are characterized as having 2.5 times higher mortality of fetuses. In recent years, examination of cell-free DNA (cfDNA) circulating in maternal plasma has become a useful noninvasive method of prenatal diagnosis. However, fetal DNA constitutes only 3-20% of plasma cfDNA during pregnancy. Short tandem repeats (STRs) are routinely used in forensic examination of DNA mixtures and are able to identify 5% minority components. Haplotypes of deletion/insertion polymorphisms and STRs (DIP-STRs) are able to detect even 0.1% minority components of DNA mixtures. Thus, STRs and DIP-STRs seem to be a perfect tool for detection of fetal alleles in DNA isolated from maternal plasma. Here, we present a novel noninvasive prenatal diagnosis technique of determination of pregnancy zygosity based on examination of feto-maternal microchimerism of plasma cfDNA with the use of STRs and DIP-STRs. Our preliminary results based on 22 STR loci showed 67% sensitivity, 100% specificity and 82% accuracy for prenatal detection of twin dizygosity. The corresponding values for seven DIP-STRs were 13%, 100% and 54%, respectively. Owing to assay performance, low DNA input requirements, low costs (below 10 USD per patient) and simplicity of analysis, genotyping of STR/DIP-STR markers in maternal plasma cfDNA may become a useful supplementary test for noninvasive prenatal diagnosis of twin zygosity in cases when chorionicity and zygosity cannot be reliably determined by ultrasound examination and prognostic value may be provided by a DNA test determining pregnancy zygosity.

Imaginaries as infrastructures? The emergence of non-invasive prenatal testing in Austria

Non-invasive prenatal testing (NIPT) is a new technology used in prenatal testing (PT) that capitalizes on genomic platforms to transform DNA fragments in the blood of pregnant women into information about the genome of a foetus. Since its market introduction in 2011, it has travelled around the globe with remarkable speed. This article engages with the emergence of NIPT in and around Vienna, the capital city of Austria, to explore why and how this technology could travel so quickly in practice. Based on a qualitative analysis of interviews, documents, and field notes, it argues, first, that NIPT could travel so quickly because it travelled as ‘adaptable boxes’ that added on to different ‘local worlds of prenatal testing (PT)’, without disrupting them. Second, in so doing, NIPT could travel on a moral and material ground, or an ‘imaginary of PT’, built in the past. Third, the article argues that elements of this imaginary were also mobilized by commercial pioneers of NIPT, who ‘infrastructurized’ extant values, practices, and networks among biomedical professionals. Thus, various actors converged in mobilizing moral and material elements of an imaginary, transforming them into an infrastructure that facilitated the travels of NIPT, while also shaping its use.

Canadian Pregnant Women's Preferences Regarding NIPT for Down Syndrome: The Information They Want, How They Want to Get It, and With Whom They Want to Discuss It

OBJECTIVE

This study sought to assess Canadian pregnant women's and their partners' preferences for information about non-invasive prenatal testing (NIPT).

METHODS

Pregnant women and their partners across Canada were surveyed as part of the Personalized Genomics for prenatal Aneuploidy Screening Using maternal blood (PEGASUS) study.

RESULTS

A total of 882 pregnant women and 395 partners participated. Women preferred being informed by a physician (77.2%). They preferred getting information ahead of time, except for information about resources for families with Down syndrome, which they preferred getting with test results. More than half thought that written consent is important (63.7%) and could decide whether to do NIPT on the day they received the information (54.9%). Women preferred to be informed of results by telephone (43.7%) or in person (28%), but they preferred in person if they were considered at high risk for Down syndrome on the basis of the results (76%). The partner was the person whose input was considered most important (62.6%). Partners' preferences were similar, except that partners tended to want information later (at the time of the test or with the results) and felt that their opinion was not considered as highly by health professionals.

CONCLUSION

Canadian women want information about NIPT early, in person, by a knowledgeable physician. Partners also want to be informed and involved in the decision-making process.

Sequencing Newborns: A Call for Nuanced Use of Genomic Technologies

Many scientists and doctors hope that affordable genome sequencing will lead to more personalized medical care and improve public health in ways that will benefit children, families, and society more broadly. One hope in particular is that all newborns could be sequenced at birth, thereby setting the stage for a lifetime of medical care and self-directed preventive actions tailored to each child's genome. Indeed, commentators often suggest that universal genome sequencing is inevitable. Such optimism can come with the presumption that discussing the potential limits, cost, and downsides of widespread application of genomic technologies is pointless, excessively pessimistic, or overly cautious. We disagree. Given the pragmatic challenges associated with determining what sequencing data mean for the health of individuals, the economic costs associated with interpreting and acting on such data, and the psychosocial costs of predicting one's own or one's child's future life plans based on uncertain testing results, we think this hope and optimism deserve to be tempered. In the analysis that follows, we distinguish between two reasons for using sequencing: to diagnose individual infants who have been identified as sick and to screen populations of infants who appear to be healthy. We also distinguish among three contexts in which sequencing for either diagnosis or screening could be deployed: in clinical medicine, in public health programs, and as a direct-to-consumer service. Each of these contexts comes with different professional norms, policy considerations, and public expectations. Finally, we distinguish between two main types of genome sequencing: targeted sequencing, where only specific genes are sequenced or analyzed, and whole-exome or whole-genome sequencing, where all the DNA or all the coding segments of all genes are sequenced and analyzed. In a symptomatic newborn, targeted or genome-wide sequencing can help guide other tests for diagnosis or for specific treatment that is urgently needed. Clinicians use the infant's symptoms (or phenotype) to interrogate the sequencing data. These same complexities and uncertainties, however, limit the usefulness of genome-wide sequencing as a population screening tool. While we recognize considerable benefit in using targeted sequencing to screen for or detect specific conditions that meet the criteria for inclusion in newborn screening panels, use of genome-wide sequencing as a sole screening tool for newborns is at best premature. We conclude that sequencing technology can be beneficially used in newborns when that use is nuanced and attentive to context.

Conflict of interest related to clinical practice is underreported: The case of noninvasive prenatal testing

Authors of policy statements from the American College of Obstetricians and Gynecologists and from the Society for Maternal-Fetal Medicine do not acknowledge the potential for their clinical income to influence their opinions, or the positions of the societies they represent. These policy statements were published in Obstetrics and Gynecology and the American Journal of Obstetrics and Gynecology, again, without acknowledgment of the potential for conflict of interest. The case of noninvasive prenatal testing, which has threatened the role of maternal-fetal medicine in the practice of prenatal screening and diagnosis, and has significantly reduced the demand for invasive prenatal diagnosis, illustrates the importance of identifying this potential conflict.

Expanding Use of cfDNA Screening in Pregnancy: Current and Emerging Ethical, Legal, and Social Issues

Purpose of Review

In 2011, screening platforms became available in the US that detect and analyze fragments of cell-free placental DNA (cfDNA) in maternal blood serum. Marketed as noninvasive prenatal tests (NIPT), cfDNA screening is more accurate than previously available serum screening tests for certain aneuploidies. The combination of a noninvasive procedure, high specificity and sensitivity, and lower false positive rates for some aneuploidies (most notably Down's syndrome) has led to broad clinician and patient adoption. New ethical, legal, and social issues arise from the increased use and expanded implementation of cfDNA in pregnancy.

Recent Findings

Recently, several professional associations have amended their guidelines on cfDNA, removing language recommending its use in only "high-risk" pregnancies in favor of making cfDNA screening an available option for women with "low-risk" pregnancies as well. At the same time, commercial cfDNA screening laboratories continue to expand the range of available test panels. As a result, the future of prenatal screening will likely include a broader range of genetic tests in a wider range of patients.

Summary

This article addresses the ethical, legal, and social issues related to the shift in guidance and expanded use of cfDNA in pregnant women, including concerns regarding routinized testing, an unmet and increasing demand for genetic counseling services, social and economic disparities in access, impact on groups living with disabling conditions, and provider liability.

Informed decision-making about prenatal cfDNA screening: An assessment of written materials

OBJECTIVES

The introduction of prenatal cfDNA screening for fetal aneuploidy and other genetic conditions has exacerbated concerns about informed decision-making in clinical prenatal testing. To assess the information provided to patients to facilitate decisions about cfDNA screening, we collected written patient education and consent documents created by laboratories and clinics.

METHODS

Informed consent documents (IC) were coded by two independent coders. Each IC was assessed for readability, attention to elements of informed consent, and completeness of information about the test and the screened conditions.

RESULTS

We found variance between IC produced by commercial laboratories versus those provided by local clinics or health care systems, and considerable variance among materials from all sources. "Commercial" IC were longer and written at a more difficult reading level than "non-commercial" IC, and were less likely to state explicitly that cfDNA only screens for certain conditions. About one-third of IC were combined with laboratory order forms. Though most IC recommended confirmatory testing for positive results, only about half clearly stated that results could be incorrect-including mentions of false positives or false negatives. About one-third of IC explicitly stated that cfDNA screening was optional. While nearly all IC from any source listed the conditions screened by the test, only about half of the IC included any phenotypic descriptions of these conditions. Few IC mentioned psychosocial considerations, and only one IC mentioned the availability of support groups for families of children with genetic conditions.

CONCLUSIONS

Based on our findings, we recommend that written and well-informed consent be sought before performing cfDNA screening, and we offer minimal and recommended standards for patient education and consent materials.

Developmental potential of clinically discarded human embryos and associated chromosomal analysis

Clinically discarded human embryos, which are generated from both normal and abnormal fertilizations, have the potential of developing into blastocysts. A total of 1,649 discarded human embryos, including zygotes containing normal (2PN) and abnormal (0PN, 1PN, 3PN and ≥4PN) pronuclei and prematurely cleaved embryos (2Cell), were collected for in vitro culture to investigate their developmental potential and chromosomal constitution using an SNP array-based chromosomal analysis. We found that blastocyst formation rates were 63.8% (for 2Cell embryos), 22.6% (2PN), 16.7% (0PN), 11.2% (3PN) and 3.6% (1PN). SNP array-based chromosomal analysis of the resultant blastocysts revealed that the percentages of normal chromosomes were 55.2% (2Cell), 60.7% (2PN), 44.4% (0PN) and 47.4% (0PN). Compared with clinical preimplantation genetic diagnosis (PGD) data generated with clinically acceptable embryos, results of the SNP array-based chromosome analysis on blastocysts from clinically discarded embryos showed similar values for the frequency of abnormal chromosome occurrence, aberrant signal classification and chromosomal distribution. The present study is perhaps the first systematic analysis of the developmental potential of clinically discarded embryos and provides a basis for future studies.

Utilization of noninvasive prenatal testing: impact on referrals for diagnostic testing

OBJECTIVE

Since the introduction of noninvasive prenatal testing (NIPT), a marked decrease in prenatal diagnostic testing (chorionic villus sampling [CVS] and amniocentesis) has been observed with unknown potential effects on genetic diagnosis of these pregnancies. The purpose of this study was to understand the impact of NIPT on genetics counseling referrals, diagnostic testing with CVS/amniocentesis, and appropriate use of NIPT.

STUDY DESIGN

A retrospective cohort study was performed on all women referred for genetic counseling and prenatal testing during the 2 years preceding the introduction of NIPT (pre-NIPT) and 2 years following (post-NIPT). The primary outcome was the difference in the number of women referred for genetic counseling and prenatal diagnosis during the pre-NIPT period compared with the post-NIPT period. The secondary outcome was the difference in the number of women referred who were not considered candidates for NIPT between the 2 study periods.

RESULTS

There was a statistically significant reduction in the number of referrals for genetic counseling and diagnostic testing in the post-NIPT compared with the pre-NIPT period (2824 vs 3944, P = .001), a reduction of 28.4%. During the post-NIPT period there was a significant reduction in referrals of women who would not be candidates for NIPT (467 pre-NIPT vs 285 post-NIPT, P = .043). In women who had diagnostic testing with CVS during the study period, 32.4% of the aneuploidies identified would not have been detected by NIPT.

CONCLUSION

There was a significant reduction in the number of patients referred for genetic counseling and prenatal diagnosis following the introduction of NIPT. In addition, there was a significant reduction in the number of patients referred for counseling and testing who would not be candidates for NIPT. This suggests that an increasing number of potential patients are being offered NIPT screening instead of diagnostic testing, including those at risk for fetal single gene disorders and aneuploidies not detectable by NIPT, potentially leading to misdiagnosis.

Overview of the impact of noninvasive prenatal testing on diagnostic procedures

Noninvasive prenatal testing (NIPT) has had a profound influence in the field of prenatal diagnosis since the 1997 discovery of cell-free fetal DNA in maternal blood. Research has progressed rapidly, with clinical data supporting laboratory studies showing that NIPT is highly sensitive and specific for fetal aneuploidy, resulting in marked uptake in the high-risk patient population. The superior accuracy of NIPT compared with conventional screening methods has led to significant decreases in the number of invasive diagnostic procedures, in addition to a concomitant decrease in the number of procedure-related fetal losses. Yet, NIPT has been described as a 'disruptive innovation' due to the considerable changes the technology has commanded on current prenatal screening and diagnostic practices. This review summarizes both institutional and global experience with NIPT uptake, its effect on reducing diagnostic invasive procedures, and the unique challenges that reduced procedural volume may have on physician and trainee proficiency, cytogenetic laboratories, and neonatal outcome.

Noninvasive prenatal testing

Noninvasive prenatal testing (NIPT) refers to recently developed genetic tests of the maternal serum that allow higher detection rates of trisomy 21 and other chromosomal aneuploidies in high-risk pregnancies. Noninvasive prenatal test analyzes cell-free DNA (cfDNA) in the maternal serum. Approximately 3% to 15% of cfDNA in the maternal blood is of fetal origin. Analysis of cfDNA can help identify fetuses affected with trisomy 21 and several other fetal aneuploidies. Testing can be performed after 9 to 10 weeks' gestation and has a higher sensitivity and specificity for trisomy 21 than other aneuploidy screening test. Noninvasive prenatal test has been studied and validated in singleton pregnancies at risk for trisomy 21 secondary to advanced maternal age, an abnormal serum screen, personal or family history of aneuploidy, or abnormal ultrasound findings, if these are suggestive of trisomy 13, 18, or 21. The utilization of NIPT for genetic screening has increased rapidly since introduction of the first clinical test in October 2011. Currently, there are limitations to NIPT including the possibility of test failure (2.6%-5.4%) and the focus on only the common trisomies. Noninvasive prenatal test is a screening test, and both false-positive (0.2%-1%) and false-negative results can occur. As the technology for NIPT is further evaluated, this test is likely to be increasingly used for prenatal screening. This review provides the obstetric clinician with an update of the current issues concerning NIPT.

Physician liability and non-invasive prenatal testing

Although non-invasive prenatal testing (NIPT) marks a notable development in the field of prenatal genetic testing, there are some physician liability considerations raised by this technology. As NIPT is still emerging as the standard of care and is just starting to receive provincial funding, the question arises of whether physicians are obligated to disclose the availability of NIPT to eligible patients as part of the physician-patient discussion about prenatal screening and diagnosis. If NIPT is discussed with patients, it is important to disclose the limitations of this technology with respect to its accuracy and the number of disorders that it can detect when compared with invasive diagnostic options. A failure to sufficiently disclose these limitations could leave patients with false assurances about the health of their fetuses and could raise informed consent and liability issues, particularly if a child is born with a disability as a result.

Amplification-free sequencing of cell-free DNA for prenatal non-invasive diagnosis of chromosomal aberrations

Cell-free DNA has been used for fetal rhesus factor and sex determination, fetal aneuploidy screening, cancer diagnostics and monitoring, and other applications. However current methods of using cell free DNA require amplification, which leads to allelic dropout and bias especially when starting with small amounts of DNA. Here we describe an amplification-free method for sequencing of cell-free DNA, even from low levels of starting material. We evaluated this method in the context of prenatal diagnosis of fetal aneuploidy and compared it with a PCR-based library preparation method as well as a recently described method using unique molecular identifiers (UMI). All methods performed well, however coverage was increased by the amplification-free method and GC-induced bias was reduced by both the amplification-free method and the UMI method. Future diagnostic applications including whole genome sequencing of cell-free DNA will benefit from amplification-free sequencing.

Impact of Cell-Free Fetal DNA Screening on Patients' Choice of Invasive Procedures after a Positive California Prenatal Screen Result

Until recently, maternal serum analyte levels paired with sonographic fetal nuchal translucency measurement was the most accurate prenatal screen available for Trisomies 18 and 21, (91% and 94% detection and false positive rates of 0.31% and 4.5% respectively). Women with positive California Prenatal Screening Program (CPSP) results have the option of diagnostic testing to determine definitively if the fetus has a chromosomal abnormality. Cell-free fetal (cff-) DNA screening for Trisomies 13, 18, and 21 was first offered in 2012, allowing women with positive screens to choose additional screening before diagnostic testing. Cff-DNA sensitivity rates are as high as 99.9% and 99.1%, with false positive rates of 0.4% and 0.1%, for Trisomies 18 and 21, respectively. A retrospective chart review was performed in 2012 on 500 CPSP referrals at the University of California, San Diego Thornton Hospital. Data were collected prior to and after the introduction of cff-DNA. There was a significant increase in the number of participants who chose to pursue additional testing and a decrease in the number of invasive procedures performed after cff-DNA screening was available. We conclude that as fetal aneuploidy screening improves, the number of invasive procedures will continue to decrease.

Attitudes towards non-invasive prenatal testing for aneuploidy among US adults of reproductive age

OBJECTIVE

To determine how adults in the United States view non-invasive prenatal testing using cell-free fetal DNA (cffDNA testing) in order to help estimate uptake.

STUDY DESIGN

A national sample of 1861 US-based adults was surveyed using a validated online survey instrument. The survey was administered by a commercial survey research company. Respondents were randomized to receive a survey about prenatal testing for trisomy 13 and 18 or trisomy 21. Participants were asked to select among testing modalities, including cffDNA testing, and rank the features of testing that they considered most important to decision making.

RESULT

There was substantive interest in the use of cffDNA testing rather than traditional screening mechanisms, with a minority of respondents reporting that they would support the use of both methods in combination. The lower rates of false-negative and false-positive test results and the ability to use the test earlier in the pregnancy were the most highly rated benefits of cffDNA testing. Participants expressed strong support for diagnostic confirmation via invasive testing after a positive result from either screening or cffDNA testing. However, almost one-third of participants reported that they would not endorse the use of either invasive or non-invasive prenatal testing.

CONCLUSION

There appears to be support for uptake of non-invasive prenatal tests. Clinical guidelines should therefore go forward in providing guidance on how to integrate non-invasive methods into the current standard of care. However, our findings indicate that even when accuracy, which is rated by patients as the most important aspect of prenatal testing, is significantly improved over existing screening methods and testing is offered non-invasively, the number of individuals who reported that they would decline any testing remained the same. Attention should therefore be directed at ensuring that the right of informed refusal of prenatal testing is not impacted by new, non-invasive methods.

Non-invasive prenatal testing for Down syndrome

Prenatal screening and diagnosis of Down syndrome and other major aneuploidies may be transformed following the identification of cell-free fetal DNA in maternal plasma at the end of the last millennium. Next generation sequencing has enabled the development of tests that accurately predict the presence of fetal trisomies by analysis of cell-free DNA in maternal blood from as early as 10 weeks of gestation. These tests are now widely available in the commercial sector but are yet to be implemented in publicly led health services. In this article we discuss the technical, social, and ethical challenges that these new tests bring.

The impact of national guidance for anomaly screening and invasive testing: unintended consequences

Recent guidance from the UK National Screening Committee (NSC) and the Fetal Anomaly Screening Programme (FASP) has led to important changes in prenatal ultrasound diagnosis and invasive testing. These relate to prenatal ultrasound investigation of what were previously known as 'soft markers' for Down's syndrome at the time of the detailed anomaly scan and as to whether full karyotype or FISH (fluorescent in situ hybridisation)/QFPCR (quantitative fluorescence PCR) testing for trisomies should be carried out when an invasive test is performed. Neither recommendation is directly related to the other but both in combination could have profound implications for the detection of chromosomal abnormalities other than trisomy 21 (Down's syndrome). In the light of two cases recently managed in one regional fetal medicine unit, we retrospectively reviewed cases where, with correct application of the NSC and FASP recommendations, non-lethal and clinically important chromosomal abnormalities would most likely not have been detected.

Perinatal outcomes in euploid pregnancies with 'double-positive' first trimester prenatal screening for trisomy 18 and 21

OBJECTIVE

The objective of this study was to investigate whether women who screened positive for both trisomy 18 (T18) and trisomy 21 (T21) yet had euploid karyotypes were at increased risk for adverse pregnancy outcomes.

STUDY DESIGN

This was a retrospective cohort study of women who had first trimester aneuploidy screening. Double-positive subjects had risks greater than screening cutoffs for T21 and T18 and confirmed euploid karyotypes. Singleton subjects were matched 1:2 by maternal age to controls with normal screening. Perinatal outcomes were investigated using t-tests and χ(2)-tests; statistical significance was set at P<0.05.

RESULT

Of 9733 women who had first trimester screening, 33 euploid pregnancies screened positive for both T21 and T18. Compared with controls, these study subjects were more likely to have abnormalities identified by prenatal ultrasounds, including renal, fetal membrane and fluid, as well as multiple anomalies (P=0.01). In addition, double-positive subjects had a lower mean gestational age at birth (P=0.02) and lower mean birth weight (P=0.03) than controls. Maternal outcomes were not significantly different.

CONCLUSION

Pregnancies with double false-positive first trimester aneuploidy screening were associated with pregnancy/fetal abnormalities.

Prenatal screening for fragile x: carriers, controversies, and counseling

In addition to causing developmental disability in future offspring, fragile X carrier status has important reproductive and mental health implications for the individual being tested. Accordingly, prenatal carrier screening and diagnosis using DNA-based molecular methods has become crucial in early detection, intervention, and family planning. Although the list of known genetic disorders is growing daily, controversy remains over who should be tested for fragile X. FMR1 gene mutations can result in inherited intellectual disability, infertility, and neurodegeneration syndromes that are encountered by clinicians in a variety of settings. Patients and clinicians are still largely unfamiliar with this disorder, its complicated inheritance, and its heterogeneous phenotype. Debate continues over who should be offered prenatal carrier screening. As more disease screening is offered, pretest counseling will become only more complex and clinicians will further struggle to balance the needs of the individual and allocation of public health resources.