495 table we have compared the chance of having an affected fetus Stiller et al. give no information about their presence or of the and women who have positive results after being screened for of sex the An indication absence. patients pregnancy to exclude and would be useful also neural-tube defects with that in four other common groups for would help another z, history whom amniocentesis is currently accepted. source of error. The small numbers of patients on which Stiller Of the women in the five groups, those with high serumet al. based their conclusions make this information essential. A.F.P. levels (>2.5 x median at 16-18 weeks gestation after We found an 18% one-year graft survival in 33 patients receivin transfusions contrast to the have been excluded by ultrasound) have 71% intraoperative only,6 multiple pregnancies ing the highest chance of having an affected fetus. When ultra(5 out of 7) survival reported by Stiller et al. Patients who had been pregnant and those with leucocyte sound is used as an additional check on gestational age some women in this group will be found to have normal levels, and antibodies in their serum were excluded in our study. We believe that only preoperative blood-transfusions have the risk of an affected fetus in the remaining women will be even greater-about 13% on the basis of our own preliminary been shown to have a beneficial effect on renal surresults in Oxford. (The risk of spina bifida alone will be about vival. Our concern is that that practice will be abandoned in favour of the perhaps simpler, but yet unproved, intraopera7%.) In addition, A.F.P. screening can be expected to identify tive transfusion. Our policy of giving at least one blood-transabout 84% of all infants with open neural-tube defects,3 fusion to patients awaiting a renal transplant will remain unwhereas in the other four groups no more than about a third of all affected fetuses will be identified. changed. While the decision to perform an amniocentesis on an indiEurotransplant Foundation, vidual patient will depend on many considerations, the risks c/o Bloodbank, G. G. PERSIJN shown in the table are likely to be an important influence. In University Hospital, Leiden, Netherlands J. J. VAN ROOD the light of these figures it would seem to be inconsistent to regard amniocentesis as unacceptable in women with high serum-A.F.p. levels but acceptable in the other groups. SCREENING FOR NEURAL-TUBE DEFECTS cator.
SIR,--Your editorial of Feb. 11 asks if neural-tube defect
screening by measurement of maternal serum alpha-fetoprotein (A.F.P.) should be introduced. The aim of such screening is to identify a group of women with a high enough risk of having an affected fetus to justify amniocentesis. While the risks RISK IN BRITAIN OF HAVING A FETUS WITH A NEURAL-TUBE
D.H.S.S. Cancer Epidemiology and Clinical Trials Unit, Department of Regius Professor of Medicine, Radcliffe Infirmary, Oxford OX2 6HE
NICHOLAS WALD HOWARD CUCKLE
Nuffield Department of Obstetrics and Gynæcology, John Radcliffe Hospital, Oxford
DEFECT OR A CHROMOSOMAL ABNORMALITY AMONG FIVE GROUPS ’ OF WOMEN FOR WHOM AMNIOCENTESIS MIGHT BE CONSIDERED
CORONARY-ARTERY BYPASS SURGERY
SIR,-The Veterans Administration paper’ has serious flaws. The survival curves in fig. 2 are labelled wrongly, as comparison with previous V.A. reports shows:2.3 the medical and surgical curves are interchanged until the point of crossover at 30 months (after which the curves are identified correctly) and the medical and surgical curves in fig. 3 are inter-
changed. consideration of the subsets of two and as a single subset on the basis of simiobstruction three-artery lar survival. Addition of the two-artery obstructions to the three-artery group in table IV improves the prognosis for medically treated patients but worsens the outlook for the surgical group. Calculation of the apparent medical and surgical mortality for obstruction of two arteries and an abnormal left ventricle does not conform to survival previously reported at 36 months.2 The numbers presented in the paper refer to randomised but not to compliant patients. Many problems in the V.A. reports would be clarified by a statement giving the numbers of medical and surgical deaths at various specific intervals (e.g., 24 and 48 months) and the numbers of compliant patients eligible to have survived the stated time, both for the whole study and for specific subsets. Reduction of the number of operative deaths would affect survival. During 1973 (the middle year of the V.A. study) our operative mortality for 1400 patients, excluding left-main coronary-artery obstructions, was 0.6%. There was a perioperative infarction-rate of about 4% and graft patency of 87% durThe
Serum-A.F.p. >2.5 x median at 16-18 weeks gestation after multiple pregnancy has been excluded by ultrasound; the figures in parentheses, based on our unpublished data, relate to pregnancies which still have high A.F.P. levels after gestational age has been checked by ultrasound. t The 84% comprises an average of 79% relating to open spina bifida only and 88% relating to anencephaly, assuming that each is equally common at birth. t These percentages are based on the frequency of chromomal abnormatmes found in mid-trimester amniotic fluid samples; the other percentages m the table are based on data at birth.
of amniocentesis are still not precisely known they do not appear to be great,I,2 and the procedure is already established clinical practice in several situations. In the accompanying 1. N.I.C.H.D. National
Registry for Amniocentesis Study Group J. Am. med. Ass. 1976, 236, 1471. 2. Simpson, N. E., Dallaire, L., Miller, J. R., Simonovich, L., Hamerton, J. L., Miller, J., McKeen, C. Can. med. Ass. J. 1976, 115, 739. 3. U.K. Collaborative Study Lancet, 1977,i, 1323. 4. Carter, C. O., David, P. A., Laurence, K. M. Med. Genet. 1968, 5, 81. 5. Galjaard, H. Cytogenet. Cell Genet. 1976, 16, 453.
5-6% operative mortality,
Registrar General’s Statistical Review for England and Wales, 1973: part I (A), tables, medical. H.M. Stationery Office. 7. Office of Population Censuses and Surveys Medical Division. Personal com-
munication. 8. Griffith, G. W. Hlth Trends, 1973, 5, 59. 1. Detre, K., Murphy, M. L., Hultgren, H. Lancet, 1977, ii, 1243. 2. Murphy, M. L., Hultgren, H. N., Petre, K. M., Thomsen, J., Takaro, T.
New Engl. J. Med. 1977, 297, 621. 3. Read, R. C., Detre, K. M., Murphy, M. L., thorac. cardiovasc. Surg. 1978, 75, 1.
N., Takaro, T. J.