c**i
发帖数: 6973 | 1 BBC Chinese, Jan 12, 2011.
http://www.bbc.co.uk/zhongwen
/simp/world/2011/01/110112_dna_test.shtml
My comment: The report is based on
Chiu RWK et al, Non-invasive prenatal assessment of trisomy 21 by
multiplexed maternal plasma DNA sequencing: large scale validity study.
British Medical Journal, 342: c7401 (2011).
http://www.bmj.com/content/342/bmj.c7401
(a) Quote from FULL TEXT (which is available free online by clicking the
button in the upper left corner of the web page):
"Cell-free DNA from the fetus has been found in the plasma of pregnant women
, and this has been used successfully for non-invasive determination of the
fetal sex and fetal RhD genotype in RhD negative women." Introduction.
"We extracted and sequenced DNA molecules from 2.0–4.8 mL of maternal
plasma using a protocol similar to that reported previously but with the
introduction of multiplexing.24 27 DNA molecules exist in maternal plasma as
short fragments. Methods.
(b) My comment:
(i) For RhD, see Rh blood group system
http://en.wikipedia.org/wiki/Rh_blood_group_system
(The Rh blood group system (including the Rh factor) is one of the currently
30 human blood group systems. It is clinically the most important blood
group system after ABO. The Rh blood group system currently consists of 50
defined blood-group antigens, among which the 5 antigens D, C, c, E, and e
are the most important ones. The commonly-used terms Rh factor, Rh positive
and Rh negative refer to the D antigen only.)
(ii) I do not know the meaning of multiplexing, which is under the heading "
Maternal plasma DNA sequencing" in Methods of full text.
(iii) sensitivity and specificity
http://en.wikipedia.org/wiki/Sensitivity_and_specificity
(Sensitivity measures the proportion of actual positives which are correctly
identified as such (e.g. the percentage of sick people who are correctly
identified as having the condition). Specificity measures the proportion of
negatives which are correctly identified (e.g. the percentage of healthy
people who are correctly identified as not having the condition).) |
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