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Prenatal Diagnosis of Hæmophilia
1327
fetal
and PEAKE and BLOOM suggested that, provided the presence of cross-reacting material was excluded in an affected family member (subsequently shown to be the case in most patients tested3), then their method should permit prenatal diagnosis of hxmophilia. Similar assays were soon described by other workers,4°5 and FIRSHEIN and colleagues6 in Connecticut have now reported their
THE LANCET
Prenatal
Diagnosis
of
Hæmophilia
eugenics has depended counselling for a sexlinked disorder—contraception or, if acceptable and safe, fetal sexing by amniocentesis, with termination of male pregnancies. Immunological tests have improved the accuracy of carrier detection. In haemophilia, plasma levels of antihxmophilic factor (factor VIII), measured by coagulation assay (VIIIC), are subnormal whereas those of the antigenic determinants of a molecule biochemically UNTIL now, haemophilia upon conventional genetic
related to it (VIIIRAg) are normal or even increased. The ratio of VIIIC to VIIIRAg may also be reduced in haemophilia carriers and determination of this ratio, together with family data and discriminant function analysis, has aided in detection of the carrier state.! Even so, this has not solved the problem for many putative carriers because they may wish to have a son and object to the 50% chance of losing a normal male fetus. Prenatal diagnosis of haemophilia would overcome some of these objections and reduce the number of terminations of pregnancy, but until lately this would have required the assay of fetal VIIIC by coagulation techniques. VIIIC is labile and its activity is destroyed as blood clots. Furthermore, amniotic fluid contains thromboplastic materials which may mimic VIIIC and affect coagulation assays; and, unlike fetal red cells, fetal plasma or serum cannot be separated from amniotic fluid or maternal plasma. Until now these technological barriers to obtaining suitably pure anticoagulated fetal plasma for VIIIC assay seemed insurmountable. Then, last year PEAKE and BLOOM in Cardiff described an immunoradiometric assay for the VIIIC antigen
(VIIICAg)-as opposed
to
VIIIRAg. VIIICAg
was
reduced in haemophilic plasma to a level equal to or often lower than that of VIIIC activity. Importantly, the antigenic determinants were stable, present in serum, and absent from and not affected by amniotic fluid. VIIICAg was detected in normal 1. Methods for the detection of haemophilia carriers Wld Hlth Org. 1977, 55, 675. 2. Peake, I. R., Bloom, A. L. Lancet, 1978, i, 473.
a
memorandum. Bull.
serum
experiences with prenatal diagnosis, correctly predicting the outcome in six fetuses at risk by determining the ratio of VIIICAg to VIIIRAg at about 18 weeks of gestation. As expected, three of the six were normal and proceeded to term. Their results are exciting but caution in interpretation is needed. Although determination of VIIIRAg was claimed to represent an internal control, their samples were diluted up to 38 times with amniotic fluid-to the limit of sensitivity of their assay for VIIICAg. Large mathematical corrections were needed from ad-hoc estimates of normal fetal haematocrit. These facts, together with the 10% variance of their assay,4suggest that advice based on this technology must be circumspect indeed. In this issue (p. 1309) Dr MIBASHAN and his colleagues, of King’s College Hospital, describe a different approach. By using a very small-bore fetoscope RODECK and CAMPBELL have obtained fetal blood-samples uncontaminated with maternal blood or amniotic fluid. By ingeniously exploiting this technique, MIBASHAN and colleagues collected fetal blood into citrate anticoagulant so carefully that they could apply a modified conventional coagulation assay for VIIIC and factor IX. The assay of factor IX, which is reduced even in the normal fetus, not only acted as a check on artefactual activation of the VIIIC assay but also, the King’s workers imply, lays the foundation for prenatal diagnosis of hxmophilia B (Christmas disease). Samples from the male fetuses of seven carriers of classical haemophilia were tested. Two gave haemophilic results and the fetuses were aborted. Normal results were obtained in the other five, of which two have been born normal and two are still in utero. The fifth fetus with normal results was aborted for other reasons and the abortus was nonhxmophilic. MIBAsHAN and colleagues took the precaution of getting the fetal and neonatal findings checked in Cardiff by the immunoradiometric assay. They also investigated the possibility of artefacts in the coagulation assay due to the (unlikely) contamination of the samples with amniotic fluid, but the experiments were few in number and are expressed as assay clotting times which are not 3 Peake, I. R, Bloom, A. L.,
Giddings, J. C., Ludlam, C. A. Br. J. Hæmat. 1979, 42, 269. 4. Lazarchick, J., Hover, L. W.J. clin. Invest. 1978, 62, 1048. 5. Reisner, H. M., Barrow, E. S., Graham, J. B Thromb. Res. 1979, 14, 235. 6 Firshein, S. I., Hoyer, L. W., Lazarchick, J., et al. New Engl. J. Med. 1979, 300, 937. 7. Roeck, C. H., Campbell, S. Br. med J. 1978, ii, 728.
1328
readily comparable with most of the fetal results. Probably the best results will be obtained by combining the King’s College Hospital sampling technique with the immunoradiometric assay; the skills needed for unambiguous coagulation assays are unlikely to be widely achieved. Of course, where such skills exist the two assays form useful mutually independent checks. Some cases of hxmophilia are sporadic and are not susceptible to prevention. No doubt the sampling problems will in future be lessened by in-vitro methods employing more accessible fetal cells. But despite these reservations and the risk to the fetus of intrauterine manipulations, prenatal diagnosis of hxmophilia now seems to be well on its way. Before it can be recommended, even at specialised centres, for routine clinical use, further predictive assessment is needed.
Malaria—the Phœnix with Resistance
Drug
ONE of the most impressive changes in social behaviour in the past 25 years has been the "continental drift" of mankind. The extension of tourism, international cultural exchange, and trade have gone hand in hand with a vast increase in air travel to the extent that, in 1977, some 630 million passengers were accommodated on all scheduled and non-scheduled international flights. The migration of labour forces too-for example, the intraEuropean movement of workers from Turkey and Spain, and the intercontinental to-ing and fro-ing of people from the Indian subcontinent to Europe —constitutes another large element ir this increasing tendency to internationalism. In addition it must be remembered that the annual pilgrimage to Mecca now involves nearly 2 million travellers from the four corners of the globe, of whom most today make the journey by air, all within one or two months. Such extensive mobility is inevitably accompanied by an increased risk of the transport of communicable diseases from one country to another. This poses a double hazard-firstly, to the individual who acquires the infection and, secondly, to the communities with which he comes into contact during or at the end of his journey. International regulations2 set out procedures to lessen these hazards. Two conditions remain serious and increasing health hazards for the traveller to the warmer parts of the world-infective hepatitis and malaria. Administration of immunoglobulin gives partial pro1. Bruce-Chwatt, L. J. Ann. Soc. beige Méd. trop. 1978, 58, 77. 2. World Health Organisation. International Health Regulations Geneva, 1974
against hepatitis, and consumption of appropriate antimalarial drugs gives certain protection against a serious attack of malaria. Despite the efficacy of antimalarial prophylaxis, acute malaria is being recognised in non-malarious countries in ever-increasing numbers of travellers. In England and Wales alone, in 1976, 1977, and 1978
tection
there
were
1178, 1486, and 1624 malaria notifica-
unpublished report from the Public Health Laboratory Service suggests that many cases are not being formally notified. The Malaria Reference Laboratory in 1978 identified 349 infections with the malignant tertian parasite Plasmodium falciparum, 1370 with P. vivax, 19 with P. malarice, and 42 with P. ovale. Together with mixed infections and some unidentified parasites
tions,3
and
an
the P.H.L.S. recorded 1909 cases. Notifications in other European countries show a parallel increase in recent years, and in many the official notifications clearly understate the true position. The Federal German- Republic reported the following numbers from 1974 to 1978: 100, 162, 203, 318, 528.4,5 Since 1970, 51people have died of malaria in that country alone. Some 2000 cases of malaria with 20 deaths were estimated to have occurred in France in 1978.6 Whereas 76% of all cases in England and Wales were acquired in the Indian subcontinent-malaria has returned there on a vast scale (thus accounting for the high proportion of P. viva.)-66.5% of cases in West Germany (between 1973 and 1977) were contracted in Africa, with a consequently higher proportion of P. falciparum (43-3%). This trend in Germany has been somewhat modified in the past few years by an increasing incidence of vivax malaria in Turkish workers-a reflection of the massive epidemic resurgence of vivax malaria in that country.An analysis of imported malaria in the U.S. between 1970 and 1976 reveals that 887 American civilians contracted malaria after returning home, 48.7% of them from Africa.8 Of the total, 31.6% had P. falciparum and 54.8% had P. vivax infections. 19 patients died, 15 from falciparum malaria and 2 from vivax infection (the vivax patients had ruptured spleens). It was estimated that (travellers to Mexico excluded), the malaria attack-rate averaged 7.7 per 100 000 overseas travellers. This rate differed strikingly in visitors to such countries as Ghana, Kenya, and Liberia, where it was 100-500 per 100 000; the global attack-rate has also increased from 12 in 1970-73, to 17-20 between 1974 and 1976. On a 3. Registrar
General’s
Weekly
Return for
England
and Wales, WR
78/52,
1978.
4. Weise, H-J. Bundesgesundheitsblatt, 1979, 22, 1. 5. Weise, H.-J. Hahnenklee symposium 1979: Malaria-Diagnose, Klinik, Therapie. Wissenschafticher Dienst, (in the press). 6. Brumpt, L. C., Petithary, J.-C., Giacomini, T. Bull. Acad. nat. Méd. 1978,
162, 395. 7. World Health Organisation. W.H.O. Chron. 1978, 32, 40. 8. López, E. C., Ruebush, T. K. II, Schulz, M. G. J. infect. Dis. 255.
1979, 139,
fetal
and PEAKE and BLOOM suggested that, provided the presence of cross-reacting material was excluded in an affected family member (subsequently shown to be the case in most patients tested3), then their method should permit prenatal diagnosis of hxmophilia. Similar assays were soon described by other workers,4°5 and FIRSHEIN and colleagues6 in Connecticut have now reported their
THE LANCET
Prenatal
Diagnosis
of
Hæmophilia
eugenics has depended counselling for a sexlinked disorder—contraception or, if acceptable and safe, fetal sexing by amniocentesis, with termination of male pregnancies. Immunological tests have improved the accuracy of carrier detection. In haemophilia, plasma levels of antihxmophilic factor (factor VIII), measured by coagulation assay (VIIIC), are subnormal whereas those of the antigenic determinants of a molecule biochemically UNTIL now, haemophilia upon conventional genetic
related to it (VIIIRAg) are normal or even increased. The ratio of VIIIC to VIIIRAg may also be reduced in haemophilia carriers and determination of this ratio, together with family data and discriminant function analysis, has aided in detection of the carrier state.! Even so, this has not solved the problem for many putative carriers because they may wish to have a son and object to the 50% chance of losing a normal male fetus. Prenatal diagnosis of haemophilia would overcome some of these objections and reduce the number of terminations of pregnancy, but until lately this would have required the assay of fetal VIIIC by coagulation techniques. VIIIC is labile and its activity is destroyed as blood clots. Furthermore, amniotic fluid contains thromboplastic materials which may mimic VIIIC and affect coagulation assays; and, unlike fetal red cells, fetal plasma or serum cannot be separated from amniotic fluid or maternal plasma. Until now these technological barriers to obtaining suitably pure anticoagulated fetal plasma for VIIIC assay seemed insurmountable. Then, last year PEAKE and BLOOM in Cardiff described an immunoradiometric assay for the VIIIC antigen
(VIIICAg)-as opposed
to
VIIIRAg. VIIICAg
was
reduced in haemophilic plasma to a level equal to or often lower than that of VIIIC activity. Importantly, the antigenic determinants were stable, present in serum, and absent from and not affected by amniotic fluid. VIIICAg was detected in normal 1. Methods for the detection of haemophilia carriers Wld Hlth Org. 1977, 55, 675. 2. Peake, I. R., Bloom, A. L. Lancet, 1978, i, 473.
a
memorandum. Bull.
serum
experiences with prenatal diagnosis, correctly predicting the outcome in six fetuses at risk by determining the ratio of VIIICAg to VIIIRAg at about 18 weeks of gestation. As expected, three of the six were normal and proceeded to term. Their results are exciting but caution in interpretation is needed. Although determination of VIIIRAg was claimed to represent an internal control, their samples were diluted up to 38 times with amniotic fluid-to the limit of sensitivity of their assay for VIIICAg. Large mathematical corrections were needed from ad-hoc estimates of normal fetal haematocrit. These facts, together with the 10% variance of their assay,4suggest that advice based on this technology must be circumspect indeed. In this issue (p. 1309) Dr MIBASHAN and his colleagues, of King’s College Hospital, describe a different approach. By using a very small-bore fetoscope RODECK and CAMPBELL have obtained fetal blood-samples uncontaminated with maternal blood or amniotic fluid. By ingeniously exploiting this technique, MIBASHAN and colleagues collected fetal blood into citrate anticoagulant so carefully that they could apply a modified conventional coagulation assay for VIIIC and factor IX. The assay of factor IX, which is reduced even in the normal fetus, not only acted as a check on artefactual activation of the VIIIC assay but also, the King’s workers imply, lays the foundation for prenatal diagnosis of hxmophilia B (Christmas disease). Samples from the male fetuses of seven carriers of classical haemophilia were tested. Two gave haemophilic results and the fetuses were aborted. Normal results were obtained in the other five, of which two have been born normal and two are still in utero. The fifth fetus with normal results was aborted for other reasons and the abortus was nonhxmophilic. MIBAsHAN and colleagues took the precaution of getting the fetal and neonatal findings checked in Cardiff by the immunoradiometric assay. They also investigated the possibility of artefacts in the coagulation assay due to the (unlikely) contamination of the samples with amniotic fluid, but the experiments were few in number and are expressed as assay clotting times which are not 3 Peake, I. R, Bloom, A. L.,
Giddings, J. C., Ludlam, C. A. Br. J. Hæmat. 1979, 42, 269. 4. Lazarchick, J., Hover, L. W.J. clin. Invest. 1978, 62, 1048. 5. Reisner, H. M., Barrow, E. S., Graham, J. B Thromb. Res. 1979, 14, 235. 6 Firshein, S. I., Hoyer, L. W., Lazarchick, J., et al. New Engl. J. Med. 1979, 300, 937. 7. Roeck, C. H., Campbell, S. Br. med J. 1978, ii, 728.
1328
readily comparable with most of the fetal results. Probably the best results will be obtained by combining the King’s College Hospital sampling technique with the immunoradiometric assay; the skills needed for unambiguous coagulation assays are unlikely to be widely achieved. Of course, where such skills exist the two assays form useful mutually independent checks. Some cases of hxmophilia are sporadic and are not susceptible to prevention. No doubt the sampling problems will in future be lessened by in-vitro methods employing more accessible fetal cells. But despite these reservations and the risk to the fetus of intrauterine manipulations, prenatal diagnosis of hxmophilia now seems to be well on its way. Before it can be recommended, even at specialised centres, for routine clinical use, further predictive assessment is needed.
Malaria—the Phœnix with Resistance
Drug
ONE of the most impressive changes in social behaviour in the past 25 years has been the "continental drift" of mankind. The extension of tourism, international cultural exchange, and trade have gone hand in hand with a vast increase in air travel to the extent that, in 1977, some 630 million passengers were accommodated on all scheduled and non-scheduled international flights. The migration of labour forces too-for example, the intraEuropean movement of workers from Turkey and Spain, and the intercontinental to-ing and fro-ing of people from the Indian subcontinent to Europe —constitutes another large element ir this increasing tendency to internationalism. In addition it must be remembered that the annual pilgrimage to Mecca now involves nearly 2 million travellers from the four corners of the globe, of whom most today make the journey by air, all within one or two months. Such extensive mobility is inevitably accompanied by an increased risk of the transport of communicable diseases from one country to another. This poses a double hazard-firstly, to the individual who acquires the infection and, secondly, to the communities with which he comes into contact during or at the end of his journey. International regulations2 set out procedures to lessen these hazards. Two conditions remain serious and increasing health hazards for the traveller to the warmer parts of the world-infective hepatitis and malaria. Administration of immunoglobulin gives partial pro1. Bruce-Chwatt, L. J. Ann. Soc. beige Méd. trop. 1978, 58, 77. 2. World Health Organisation. International Health Regulations Geneva, 1974
against hepatitis, and consumption of appropriate antimalarial drugs gives certain protection against a serious attack of malaria. Despite the efficacy of antimalarial prophylaxis, acute malaria is being recognised in non-malarious countries in ever-increasing numbers of travellers. In England and Wales alone, in 1976, 1977, and 1978
tection
there
were
1178, 1486, and 1624 malaria notifica-
unpublished report from the Public Health Laboratory Service suggests that many cases are not being formally notified. The Malaria Reference Laboratory in 1978 identified 349 infections with the malignant tertian parasite Plasmodium falciparum, 1370 with P. vivax, 19 with P. malarice, and 42 with P. ovale. Together with mixed infections and some unidentified parasites
tions,3
and
an
the P.H.L.S. recorded 1909 cases. Notifications in other European countries show a parallel increase in recent years, and in many the official notifications clearly understate the true position. The Federal German- Republic reported the following numbers from 1974 to 1978: 100, 162, 203, 318, 528.4,5 Since 1970, 51people have died of malaria in that country alone. Some 2000 cases of malaria with 20 deaths were estimated to have occurred in France in 1978.6 Whereas 76% of all cases in England and Wales were acquired in the Indian subcontinent-malaria has returned there on a vast scale (thus accounting for the high proportion of P. viva.)-66.5% of cases in West Germany (between 1973 and 1977) were contracted in Africa, with a consequently higher proportion of P. falciparum (43-3%). This trend in Germany has been somewhat modified in the past few years by an increasing incidence of vivax malaria in Turkish workers-a reflection of the massive epidemic resurgence of vivax malaria in that country.An analysis of imported malaria in the U.S. between 1970 and 1976 reveals that 887 American civilians contracted malaria after returning home, 48.7% of them from Africa.8 Of the total, 31.6% had P. falciparum and 54.8% had P. vivax infections. 19 patients died, 15 from falciparum malaria and 2 from vivax infection (the vivax patients had ruptured spleens). It was estimated that (travellers to Mexico excluded), the malaria attack-rate averaged 7.7 per 100 000 overseas travellers. This rate differed strikingly in visitors to such countries as Ghana, Kenya, and Liberia, where it was 100-500 per 100 000; the global attack-rate has also increased from 12 in 1970-73, to 17-20 between 1974 and 1976. On a 3. Registrar
General’s
Weekly
Return for
England
and Wales, WR
78/52,
1978.
4. Weise, H-J. Bundesgesundheitsblatt, 1979, 22, 1. 5. Weise, H.-J. Hahnenklee symposium 1979: Malaria-Diagnose, Klinik, Therapie. Wissenschafticher Dienst, (in the press). 6. Brumpt, L. C., Petithary, J.-C., Giacomini, T. Bull. Acad. nat. Méd. 1978,
162, 395. 7. World Health Organisation. W.H.O. Chron. 1978, 32, 40. 8. López, E. C., Ruebush, T. K. II, Schulz, M. G. J. infect. Dis. 255.
1979, 139,