Ο NYBERG ΧΡΗΣΙΜΟΠΟΙΕΙ ΤΟ ΓΝΩΣΤΟ ΠΡΩΤΟΚΟΛΛΟ AAURA ΚΑΝΩΝΤΑΣ ΧΡΗΣΗ 6 SOFT MARKERS ΚΑΙ Ο ΠΡΩΤΟΣ ΠΑΓΚΟΣΜΙΑ ΠΟΥ ΛΑΜΒΑΝΕΙ ΥΠΟΨΙΝ ΤΟΥ ΤΟ BACKROUND RISK ΤΗΣ ΚΑΘΕ ΓΥΝΑΙΚΑΣ (ΗΛΙΚΙΑ / ΠΡΟΗΓΟΥΜΕΝΟ SCREENING ) ΚΑΙ ΤΟ ΠΟΛΑΠΛΑΣΙΑΖΕΙ ΜΕ ΤΟ LIKELIHOOD RATIO ΤΟΥ ΚΑΘΕ ΔΕΙΚΤΗ ΞΕΧΩΡΙΣΤΑ.
J ULTRA MED 2001;20;1053-1063
το πρωτοκολλο AAURA /www.fetalcenter.org
SENSITIVITY 85 % ME 14.2 FPR
Major abnormalities are observed in fewer than 25% of affected fetuses in most studies,
1,7,26,27 whereas 1 or more soft markers may be
observed in 50% or more cases.5,7,28,29 This
emphasizes the importance of soft markers for
detection of fetal trisomy 21 on secondtrimester
sonography, especially among highrisk
women in whom high sensitivity is
desirable. On the other hand, the false-positive
rate may be unacceptably high (13%–17%) if any
one of a panel of markers is detected among
Major abnormalities were considered to be cardiac
defects, hydrops, cystic hygroma with
internal septation, and duodenal atresia.
Nonstructural markers that were evaluated
included nuchal thickening (≥5 mm), pyelectasis
(renal pelvis ≥3 mm), hyperechoic bowel
(grades 2 and 3), EIF, and extremity shortening
(humerus or femur shortening). Mild cerebral
ventricular dilatation (lateral ventricle 10–15
mm) was not considered a structural abnormality
and was not separately considered as a sonographic
marker in this series.
Four markers (nuchal thickening, hyperechoic
bowel, shortened humerus, and EIF) were found
to be statistically associated with an increased
risk of trisomy 21 as isolated findings. The 2
remaining markers (shortened femur and
pyelectasis) were also associated with trisomy 21
overall, although this association did not reach
statistical significance when these markers were
isolated findings. If these 2 markers are omitted,
then the false-positive rate of any marker would
decrease from 13% to 6.9%, and the sensitivity
would decrease from 52.1% to 44.6%.
Nuchal thickening (P < .001; likelihood ratio, 11) and hyperechoic
bowel (P < .001; likelihood ratio, 6.7) showed the strongest association with trisomy 21 as isolated
markers, followed by shortened humerus (likelihood ratio, 5.1), echogenic intracardiac focus (likelihood
ratio, 1.8), shortened femur (likelihood ratio, 1.5), and pyelectasis (likelihood ratio, 1.5).
Echogenic intracardiac focus was the single most common isolated marker in both affected fetuses
(7.1%) and control fetuses (3.9%) but carried a low risk (P = .046; likelihood ratio, 1.8).
The risk of fetal Down syndrome, reflected by likelihood ratios, was determined for 6 individual
markers. This information can be combined with the a priori risk to estimate the individual
patient risk for fetal Down syndrome.
The presence of any marker,
however, will result in a high false-positive rate if
the presence of any single marker is considered
a positive finding. This approach can understandably
lead to considerable anxiety32 and
inconsistent management33 when a single
marker is identified among low-risk patients.
The false-positive rate can be appropriately
lowered among younger women by considering
the a priori risk.34–36With the use of the model of
age-adjusted ultrasound risk assessment
(AAURA),7 an individual patient-specific risk can
be estimated by the presence or absence of
sonographic markers combined with the a priori
risk based on maternal age. Because sonographic
findings appear to be largely independent of
both maternal age and biochemical analytes,
37–39 we think the risk from biochemical
screening (serum markers plus maternal age
risk) can be substituted for maternal age risk
alone when known.
In conclusion, a single marker is commonly
encountered for both fetuses with trisomy 21
(22.6%) and fetuses without abnormalities (11.3%).
Four markers (nuchal thickening, echogenic
bowel, shortened humerus, and EIF) were found to
be statistically associated with trisomy 21, even as
isolated findings. The degree of risk associated with
each of the sonographic markers was calculated
with LRs. This information can be integrated with
the patient’s a priori risk to provide an individual
risk for both high- and low-risk patients.