Staying the course

Advances in non-invasive prenatal diagnosis continue in spite of our ability, albeit limited, to obtain a fetal karyotype from the maternal circulation. This month’s article from the Harris Birthright Research Centre in collaboration with Ohio State University on nasal bone hypoplasia in trisomy 21 between 15 and 22 weeks’ gestation1 is an extension of the pioneering work on the ultrasound diagnosis of aneuploidy2. This work follows closely the pattern established in landmark studies in the first trimester with nuchal translucency (NT) and later nasal bone hypoplasia3. Observations alone do not make for a change in clinical practice. It is the exhaustive study of these observations in a large population that will provide the evidence required to modify clinical practice. Cicero et al.1 have extrapolated their findings of an association in the first trimester to the second trimester so that, from an initial case report4, we now have a large series of cases that not only clearly demonstrates the significance of this finding at a particular stage of gestation (15–22 weeks) but also begins to suggest a difference between Caucasian and Afro-Caribbean populations. The strength of this study stems from a meticulous desire for quality and reproducibility. While retrospective studies on ‘nasal bone hypoplasia’ have been presented, a prospective approach is required to arrive at a sound conclusion. The work of The Fetal Medicine Foundation (FMF) has shown that only by developing an ongoing quality assurance program can these data be reproducible and clinically useful. Their well-known requirement of completion of a theoretical course followed by case submission and regular audits has been shown to be successful5. In fact we have shown that even in expert hands this feedback is essential to produce quality results6. Others have suggested that, without these strict requirements, first-trimester screening has limited value7. In this regard one must worry when articles advocate the use of these ultrasound parameters without implementation of the associated quality assurance programs. A recent article claims a 100% success rate in identifying trisomy between 10 and 14 weeks. While an undescribed rigorous audit was performed and the use of well-trained, experienced operators was stated8, it is hard to believe the reproducibility of this study when the data from the FMF based on well over 100 000 cases suggest the need to incorporate biochemical assessment to approach a 90% detection rate. More likely this study requires many more patients to confirm this observation and insure that there is 100% ascertainment. Also of concern was a study published recently in this journal9 that provides a table to use for the ‘bedside’ evaluation of NT and risk of aneuploidy. The authors suggest that, by making this chart available, the ability to perform first-trimester screening will not be limited to those who have met the FMF criteria and require the computerized program, but will be available to anyone who has a copy of the charts. To me, this is a major step backwards for the very reasons described above. Quality assurance programs must be integrated into all aspects of clinical medicine if these new innovations are to withstand the test of time and not simply be fads. The FMF has led the way in this process for ultrasound screening and we must not allow the temptation for an easy way out to negate the more scientifically correct methodologies. Further, it must be emphasized that the FMF provides this software and auditing process at no cost to the sonographer as stated by Herman et al. Having personally been involved in teaching many of these courses endorsed by the FMF, I can state that the value of these offerings, as reflected in course evaluations by the participants, outweighs any inconvenience and cost. While Herman et al.’s paper9 has undergone the strict peer review process we require for this journal, I would continue to urge extreme caution in interpreting the results of a first-trimester scan based simply on a chart. Ultimately, the success and accuracy of an ultrasound-based screening program will still depend more on the skill and experience of the operator than on the widespread availability of risk assessment data in print format. Thus, the quality assurance programs promoted by the FMF as well as other organizations such as the American Institute of Ultrasound in Medicine and the American College of Radiology should be emulated by all those involved in the practice of ultrasound screening.