1538
Mis-sense mutation
of &agr;1-antichymotrypsin
gene associated with chronic lung disease SiR,,-Genetic deficiency of the serum proteinase inhibitor al-antichymotrypsin (al-ACT) has been observed at a frequency of about 1 in 300 in a Swedish population. 1 eli-ACT inhibits neutrophil cathepsin G and mast cell chymase, but its physiological function has not yet been identified. It is synthesised and secreted by hepatocytes and by alveolar macrophages and is detectable in lung lavage fluid. A role for eli-ACT in defending the lung against proteolytic attack is suggested by an association between al-ACT deficiency and disturbances of lung function.2 We have described a patient with ell-ACT deficiency and chronic lung disease who also had massive intrahepatic storge of cx,-ACT.1 To study the molecular basis of disease in patients with eli-ACT
deficiency we have cloned the human ell-ACT gene from a cosmid library.3 After partial sequencing of the gene we developed primers for the amplifiction of the five exons and the splice sites with polymerase chain reaction (PCR): Size of
product
Detection of a,-ACT gene mutation by direct automated sequencing of PCR-amplified genomic DNA.
ell-ACT seems to be a novel genetic defect predisposing to COPD. 1 he underlying mechanism might be impaired protection against protease-induced lung injury. The mutant protein may also accumulate in the liver in some carriers but the frequency of clinically relevant liver disease in carriers is not yet known. Supported by Bundesministerium fur Forschung und Technologie, grant 01KE8903/6.
*c
=
coding,
a
=
anticoding.
Direct sequencing of PCR products was done by an automated DNA sequencer’ (see figure). eli-ACT serum concentrations were measured by rocket immunoelectrophoresis and are expressed as i percentage of a serum pool standard. Sequence analysis of the oq-ACT genes in the patient with al-ACT deficiency and hepatic oq-ACT storage revealed him to be heterozygous for a point mutation in exon III, changing Pro227 -+Ala (CCT-->GCT), this mutation being the only molecular abnormality of the genes in this case. The mutation is also detectable by PCR: the region of interest is amplified by primers 5’-ACTCCAGAGAGTCTCTCCAC-3’ and 5’-TATGAGGACTCTGGGCACTTC-3’. The PCR product of size 366 bp is then cut with Alul. The normal sequence releases a fragment of size 227 bp; the mutant sequence releases fragments of size 207 bp and 20 bp instead. We have screened 100 patients with chronic obstructive pulmonary disease (COPD) and 100 healthy controls for this mutation and we detected it in 4 COPD patients but in none of the controls (p = 0-04). All carriers of the mutation had subnormal ell-ACT serum levels. ol-ACT concentrations of patients and controls were:
a, -ACT (%) as mean (SD) (range)
in:
University Medical Clinic and Polyclinic, Klinikum Bergmannsheil, University of Bochum, 4630 Bochum, Germany, Institute for Clinical Biochemistry, University of Bonn; Institute for Anthropology and Human Genetics, University of Munich, and Malmo General Hospital, University of Lund, Malmo, Sweden
W. POLLER J.-P. FABER S. SCHOLZ S. WEIDINGER K. BARTHOLOMÉ K. OLEK S. ERIKSSON
B,Lilja H. Familial &agr;1-antichymotrypsin deficiency. Acta Med Scand 1986; 220: 447-53. Lindmark BE, Arborelius M, Eriksson SG. Pulmonary function in middle-aged women with heterozygous deficiency of the senne protease inhibitor &agr;1antichymotrypsin. Am Rev Respir Dis 1990; 141: 884-88. Poller W, Faber J-P, Klobeck G, Olek K. Cloning of the human &agr;2-macroglobulin gene and detection of mutations in two functional domains: the bait region and the thiolester site. Human Genet (m press). Faber J-P, Kochhan L, Bormann M, et al. Automated direct sequencing. Biotech Forum Eur 1991; 8: 44-45. Faber J-P, Poller W, Weidinger S, Lindmark B, Eriksson S, Olek K. Identification of point mutations in the &agr;1-antichymotrypsin gene. Am J Hum Genet 1991; 49 (suppl): 134. Eriksson S, Carlson J, Velez R. Risk of cirrhosis and primary liver cancer in &agr;-antitrypsin deficiency. N Engl J Med 1986; 314: 736-39. Crystal RG. &agr;1-antitrypsin deficiency, emphysema, and liver disease. J Clin Invest
1. Eriksson S, Lindmark 2.
3.
4.
5.
6. 7.
1990; 85: 1343-52.
Diphtheria, pertussis, and tetanus vaccination
Isoelectric focusing of the ell-ACT in carriers of the mutation showed no abnormalities. The deficient individuals also had normal ell-ACT -antitrypsin serum concentrations and phenotypes (Pi
MM).
previously described common sequence polymorphism (Ala-17Thr) in the signal peptide of the ell-ACT genes was not associated with abnormal serum o-ACT or disease. In contrast, the point mutation described here was associated with both ell-ACT and chronic lung disease in 4 cases. Intrahepatic storage of ell-ACT was found in 1 of them, when biopsy for cryptogenic liver cirrhosis was done. The other 3 patients had no clinical or biochemical A
evidence of liver disease and biopsies were not done. The clinical and laboratory features associated with the o-ACT gene mutation closely resemble those associated with the Z-mutation of the ell-antitrypsin gene, and homozygotes for that mutation are at very high risk of COPD; in a few of them liver cirrhosis and hepatic al-antitrypsin storage also develop.6,? The Pro22? --+Ala mutation of
SIR,-Dr Cutts and Dr Begg (May 30, p 1355) are in agreement with us that routine immunisation policies should be based on sound data and that there is a need for appropriate studies on immune responses of UK infants given routine diphtheriapertussis-tetanus immunisation according to the accelerated schedule at 2, 3, and 4 months of age. The need for these studies is not in conflict with the indubitable advantages of an accelerated immunisation programme-eg, improved uptake and earlier protection against pertussis. Cutts and Begg suggest that ELISA testing for antibodies against tetanus and diphtheria may not correlate well with in-vivo neutralisation testing for antibody concentrations below 01 IU/n-d. However, Melville-Smith and coworkers’ reported evidence suggestive of close correlation between ELISA and the toxin neutralisation test in mice for the measurement of low levels of tetanus toxoid antibody (ie, < 0’ 1 IU/ml) in human sera. We agree that longer term follow-up studies are needed to ascertain the proportion of infants whose antibody concentrations against tetanus
1539
and diphtheria fall below 0-1
IU/ml, and our data will be available
shortly. Cutts and Begg object to implications for developing countries being drawn from our study and they cite a report of lower efficiency of transfer of transplacental antibodies to tetanus toxoid antibodies in African than in French infants.2 However, that study clearly showed that higher levels of tetanus toxoid antibody were
transferred to African infants if their mothers had been immunised
during pregnancy. The critical point is that protection against neonatal tetanus results from passively acquired antibodies and, as shown by studies in Thailand,3these can suppress the response to active immunisation of 2-month-old infants with tetanus toxoid. Our investigations in Oxford (Feb 29, p 507) also indicate that in infants with high maternal antibody concentrations, lower titres of serum antibodies to tetanus and pertussis are evident at 5 months of age after completion of the primary course of three immunisations at 2, 3, and 4 months of age. Thus, despite the clear overall benefits of both the accelerated programme of immunisation and immunisation of pregnant mothers against tetanus, there is a need to recognise the potential difficulties that may arise from the reduction in immune responses resulting from (i) suppression by passively acquired maternal antibodies and (ii) possible immune immaturity. If protection decreases over time, further natural exposure to diphtheria or pertussis may result in disease. ROBERT BOOY E. RICHARD MOXON RICHARD T. MAYON-WHITE STUART J. AITKEN HELEN GRIFFITHS HELEN M. CHAPEL
Department of Paediatrics, John Radcliffe Hospital,
Headington, Oxford OX3 9DU, UK
1. Melville-Smith ME, Seagroatt VA, Watkins JT. A comparison of enzyme-linked immunosorbent assay (ELISA) with the toxin neutralization test m mice as a method for the estimation of tetanus anti-toxin in human sera. J Biol Stand 1983; 11: 137-44. 2. Gendrel D, Richard-Lenobele D, Picaud C, Francoual C, Blot P. Placental transfer of tetanus antibodies and protection of the newborn. J Trop Paediatr 1990; 36: 279-82. 3. Sangpetchsong V, Impat A, Dhiensiri K, Podhipala A. Effect of passive immunity to tetanus in DTP vaccinated infants. SE Asian J Trop Med Pub Health 1985; 16: 117-23.
Cystic fibrosis carrier screening at first diagnosis of pregnancy in general practice SiR,—Several pilot programmes for cystic fibrosis (CF) carrier screening in the general British population are now being evaluated (see, for example, Watson et all). Strategies investigated involve pre-pregnancy screening, when patient motivation and later recall may be low; or hospital antenatal clinic screening, when there is little time for counselling and reflection and where positive tests lead to undesirably late termination of pregnancy. We report here a successful pilot study of an alternative approach-namely, testing offered at first diagnosis of pregnancy, allowing carrier testing to be completed within the first trimester and allowing discussion of reproductive options and antenatal diagnosis without undue pressure.
The study is based in a south Manchester two-partner training general practice (population 4400) in which there are 50-60 births per year. A preliminary feasibility survey in 1990, the year before the pilot study, showed that 96% of pregnancies were diagnosed at 6-14 weeks (average 8 weeks). However, this early opportunity for screening was generally lost because the average delay between first GP
booking and first hospital antenatal
clinic
appointment was 4
weeks, taking many patients into the second trimester. From Sept 1, 1991, CF carrier screening has been offered to all patients at the time of the antenatal booking consultation at the practice. This consultation includes routine general medical history, obstetric history, and choice of place of delivery. An explanatory leaflet is given, after discussion of CF carrier screening within the context of other antenatal tests offered during pregnancy. After permission has been obtained, patients are randomised to maternal or to couple testing. A saliva sample is obtained from the woman at
that time and
women
in the
couple-testing
group
are
asked to obtain a saliva sample from the father. They take home the leaflet with a sample kit for their partner to be returned the following morning. The results of the test, with a risk estimation for the pregnancy, are sent to the patients by post within 10 days with a copy to the GP. Laboratory tests involve four gene probes (AF508, G551D, G542X, 621 + 1G > T), detecting 83.5% of CF carriers in our
population.
So far 44 pregnancies have been screened. 1 carrier has been detected in the maternal-testing group; her partner tested negative. 2 carriers were detected in the couple-testing group, and both partners tested negative. 1 partner in the couple-testing group declined the test and the maternal sample tested negative. 14 pregnancies were not included in the pilot study, for the following reasons: 1 patient aged 17 years declined the test, then requested termination, changed her mind, and delivered prematurely; 4 booked after 14 weeks for antenatal care; 7 requested termination for reasons unrelated to CF; and 2 patients miscarried before antenatal booking. Preliminary results from questionnaires and interview indicate that women have a positive attitude to CF carrier screening and to general practice as the preferred place for counselling and testing. There is no evidence at this stage that the procedure has caused excessive anxiety (Spielberger scale). Our study will be extended to other local general practices because we believe that general practice provides the ideal setting for very early pregnancy screening and general genetic counselling. Here it becomes an integral part of primary health care and permits assessment of the psychological impact of screening on patients, partners, and families. This is a valuable model for the closer integration of primary and secondary health-care services. This work is supported by the Wolfson Foundation and the North Western Regional Health Authority. Brooklands Medical Practice,
H.
J. HARRIS
Manchester
D. SCOTCHER
Department of Medical Genetics, St Mary’s Hospital, Manchester M13 OJH, UK
D. CRAUFURD A. WALLACE R. HARRIS
Mayall E, Chapple J, et al. Screening for carriers of cystic fibrosis through primary health care services. Br Med J 1991; 303: 504-07.
1. Watson EK,
Population screening for cystic fibrosis SIR,-We are involved in a pilot project of population screening for cystic fibrosis (CF) carriers, using mouthwash samples to screen for four mutations (AF508, G551D, G542X, 621 + 1G>T). We offered all members of staff in our division of molecular and medical genetics confidential screening for carrier status and report here the uptake of testing in this genetically interested and informed group of adults, predominantly of reproductive age. In December, 1991, three posters advertising the availability of confidential screening were displayed prominently, giving two contact names (a clinical geneticist and a nurse genetics counsellor). Those requesting screening were given an information leaflet (devised for our population screening programme) and then interviewed privately to establish whether there was a family history of CF, to check that they understood the inheritance of CF, and to confirm that neither they, their partner, nor anyone else in their family were pregnant. We also reminded them that a negative test result would reduce their carrier risk (to 1 in 130 for caucasians), but not eliminate it. Each mouthwash sample was given a coded reference number, the identity being known only to the clinicians offering the service. The results were handed to staff members personally one week later, together with a copy for them to pass on to their general practitioner. There are 110 members of staff in the division, of whom 80 are female (73%). 18 requested screening during the first three days, and 5 more presented a month later, while being screened for hepatitis B immunity status, when a personal verbal offer of CF screening was made. Of the 23 staff requesting screening, 20 were female (87%). 1 female had her test postponed because a relative was in late pregnancy at that time. The uptake rate for CF carrier screening was therefore about 20%. No carriers were detected.
Mis-sense mutation
of &agr;1-antichymotrypsin
gene associated with chronic lung disease SiR,,-Genetic deficiency of the serum proteinase inhibitor al-antichymotrypsin (al-ACT) has been observed at a frequency of about 1 in 300 in a Swedish population. 1 eli-ACT inhibits neutrophil cathepsin G and mast cell chymase, but its physiological function has not yet been identified. It is synthesised and secreted by hepatocytes and by alveolar macrophages and is detectable in lung lavage fluid. A role for eli-ACT in defending the lung against proteolytic attack is suggested by an association between al-ACT deficiency and disturbances of lung function.2 We have described a patient with ell-ACT deficiency and chronic lung disease who also had massive intrahepatic storge of cx,-ACT.1 To study the molecular basis of disease in patients with eli-ACT
deficiency we have cloned the human ell-ACT gene from a cosmid library.3 After partial sequencing of the gene we developed primers for the amplifiction of the five exons and the splice sites with polymerase chain reaction (PCR): Size of
product
Detection of a,-ACT gene mutation by direct automated sequencing of PCR-amplified genomic DNA.
ell-ACT seems to be a novel genetic defect predisposing to COPD. 1 he underlying mechanism might be impaired protection against protease-induced lung injury. The mutant protein may also accumulate in the liver in some carriers but the frequency of clinically relevant liver disease in carriers is not yet known. Supported by Bundesministerium fur Forschung und Technologie, grant 01KE8903/6.
*c
=
coding,
a
=
anticoding.
Direct sequencing of PCR products was done by an automated DNA sequencer’ (see figure). eli-ACT serum concentrations were measured by rocket immunoelectrophoresis and are expressed as i percentage of a serum pool standard. Sequence analysis of the oq-ACT genes in the patient with al-ACT deficiency and hepatic oq-ACT storage revealed him to be heterozygous for a point mutation in exon III, changing Pro227 -+Ala (CCT-->GCT), this mutation being the only molecular abnormality of the genes in this case. The mutation is also detectable by PCR: the region of interest is amplified by primers 5’-ACTCCAGAGAGTCTCTCCAC-3’ and 5’-TATGAGGACTCTGGGCACTTC-3’. The PCR product of size 366 bp is then cut with Alul. The normal sequence releases a fragment of size 227 bp; the mutant sequence releases fragments of size 207 bp and 20 bp instead. We have screened 100 patients with chronic obstructive pulmonary disease (COPD) and 100 healthy controls for this mutation and we detected it in 4 COPD patients but in none of the controls (p = 0-04). All carriers of the mutation had subnormal ell-ACT serum levels. ol-ACT concentrations of patients and controls were:
a, -ACT (%) as mean (SD) (range)
in:
University Medical Clinic and Polyclinic, Klinikum Bergmannsheil, University of Bochum, 4630 Bochum, Germany, Institute for Clinical Biochemistry, University of Bonn; Institute for Anthropology and Human Genetics, University of Munich, and Malmo General Hospital, University of Lund, Malmo, Sweden
W. POLLER J.-P. FABER S. SCHOLZ S. WEIDINGER K. BARTHOLOMÉ K. OLEK S. ERIKSSON
B,Lilja H. Familial &agr;1-antichymotrypsin deficiency. Acta Med Scand 1986; 220: 447-53. Lindmark BE, Arborelius M, Eriksson SG. Pulmonary function in middle-aged women with heterozygous deficiency of the senne protease inhibitor &agr;1antichymotrypsin. Am Rev Respir Dis 1990; 141: 884-88. Poller W, Faber J-P, Klobeck G, Olek K. Cloning of the human &agr;2-macroglobulin gene and detection of mutations in two functional domains: the bait region and the thiolester site. Human Genet (m press). Faber J-P, Kochhan L, Bormann M, et al. Automated direct sequencing. Biotech Forum Eur 1991; 8: 44-45. Faber J-P, Poller W, Weidinger S, Lindmark B, Eriksson S, Olek K. Identification of point mutations in the &agr;1-antichymotrypsin gene. Am J Hum Genet 1991; 49 (suppl): 134. Eriksson S, Carlson J, Velez R. Risk of cirrhosis and primary liver cancer in &agr;-antitrypsin deficiency. N Engl J Med 1986; 314: 736-39. Crystal RG. &agr;1-antitrypsin deficiency, emphysema, and liver disease. J Clin Invest
1. Eriksson S, Lindmark 2.
3.
4.
5.
6. 7.
1990; 85: 1343-52.
Diphtheria, pertussis, and tetanus vaccination
Isoelectric focusing of the ell-ACT in carriers of the mutation showed no abnormalities. The deficient individuals also had normal ell-ACT -antitrypsin serum concentrations and phenotypes (Pi
MM).
previously described common sequence polymorphism (Ala-17Thr) in the signal peptide of the ell-ACT genes was not associated with abnormal serum o-ACT or disease. In contrast, the point mutation described here was associated with both ell-ACT and chronic lung disease in 4 cases. Intrahepatic storage of ell-ACT was found in 1 of them, when biopsy for cryptogenic liver cirrhosis was done. The other 3 patients had no clinical or biochemical A
evidence of liver disease and biopsies were not done. The clinical and laboratory features associated with the o-ACT gene mutation closely resemble those associated with the Z-mutation of the ell-antitrypsin gene, and homozygotes for that mutation are at very high risk of COPD; in a few of them liver cirrhosis and hepatic al-antitrypsin storage also develop.6,? The Pro22? --+Ala mutation of
SIR,-Dr Cutts and Dr Begg (May 30, p 1355) are in agreement with us that routine immunisation policies should be based on sound data and that there is a need for appropriate studies on immune responses of UK infants given routine diphtheriapertussis-tetanus immunisation according to the accelerated schedule at 2, 3, and 4 months of age. The need for these studies is not in conflict with the indubitable advantages of an accelerated immunisation programme-eg, improved uptake and earlier protection against pertussis. Cutts and Begg suggest that ELISA testing for antibodies against tetanus and diphtheria may not correlate well with in-vivo neutralisation testing for antibody concentrations below 01 IU/n-d. However, Melville-Smith and coworkers’ reported evidence suggestive of close correlation between ELISA and the toxin neutralisation test in mice for the measurement of low levels of tetanus toxoid antibody (ie, < 0’ 1 IU/ml) in human sera. We agree that longer term follow-up studies are needed to ascertain the proportion of infants whose antibody concentrations against tetanus
1539
and diphtheria fall below 0-1
IU/ml, and our data will be available
shortly. Cutts and Begg object to implications for developing countries being drawn from our study and they cite a report of lower efficiency of transfer of transplacental antibodies to tetanus toxoid antibodies in African than in French infants.2 However, that study clearly showed that higher levels of tetanus toxoid antibody were
transferred to African infants if their mothers had been immunised
during pregnancy. The critical point is that protection against neonatal tetanus results from passively acquired antibodies and, as shown by studies in Thailand,3these can suppress the response to active immunisation of 2-month-old infants with tetanus toxoid. Our investigations in Oxford (Feb 29, p 507) also indicate that in infants with high maternal antibody concentrations, lower titres of serum antibodies to tetanus and pertussis are evident at 5 months of age after completion of the primary course of three immunisations at 2, 3, and 4 months of age. Thus, despite the clear overall benefits of both the accelerated programme of immunisation and immunisation of pregnant mothers against tetanus, there is a need to recognise the potential difficulties that may arise from the reduction in immune responses resulting from (i) suppression by passively acquired maternal antibodies and (ii) possible immune immaturity. If protection decreases over time, further natural exposure to diphtheria or pertussis may result in disease. ROBERT BOOY E. RICHARD MOXON RICHARD T. MAYON-WHITE STUART J. AITKEN HELEN GRIFFITHS HELEN M. CHAPEL
Department of Paediatrics, John Radcliffe Hospital,
Headington, Oxford OX3 9DU, UK
1. Melville-Smith ME, Seagroatt VA, Watkins JT. A comparison of enzyme-linked immunosorbent assay (ELISA) with the toxin neutralization test m mice as a method for the estimation of tetanus anti-toxin in human sera. J Biol Stand 1983; 11: 137-44. 2. Gendrel D, Richard-Lenobele D, Picaud C, Francoual C, Blot P. Placental transfer of tetanus antibodies and protection of the newborn. J Trop Paediatr 1990; 36: 279-82. 3. Sangpetchsong V, Impat A, Dhiensiri K, Podhipala A. Effect of passive immunity to tetanus in DTP vaccinated infants. SE Asian J Trop Med Pub Health 1985; 16: 117-23.
Cystic fibrosis carrier screening at first diagnosis of pregnancy in general practice SiR,—Several pilot programmes for cystic fibrosis (CF) carrier screening in the general British population are now being evaluated (see, for example, Watson et all). Strategies investigated involve pre-pregnancy screening, when patient motivation and later recall may be low; or hospital antenatal clinic screening, when there is little time for counselling and reflection and where positive tests lead to undesirably late termination of pregnancy. We report here a successful pilot study of an alternative approach-namely, testing offered at first diagnosis of pregnancy, allowing carrier testing to be completed within the first trimester and allowing discussion of reproductive options and antenatal diagnosis without undue pressure.
The study is based in a south Manchester two-partner training general practice (population 4400) in which there are 50-60 births per year. A preliminary feasibility survey in 1990, the year before the pilot study, showed that 96% of pregnancies were diagnosed at 6-14 weeks (average 8 weeks). However, this early opportunity for screening was generally lost because the average delay between first GP
booking and first hospital antenatal
clinic
appointment was 4
weeks, taking many patients into the second trimester. From Sept 1, 1991, CF carrier screening has been offered to all patients at the time of the antenatal booking consultation at the practice. This consultation includes routine general medical history, obstetric history, and choice of place of delivery. An explanatory leaflet is given, after discussion of CF carrier screening within the context of other antenatal tests offered during pregnancy. After permission has been obtained, patients are randomised to maternal or to couple testing. A saliva sample is obtained from the woman at
that time and
women
in the
couple-testing
group
are
asked to obtain a saliva sample from the father. They take home the leaflet with a sample kit for their partner to be returned the following morning. The results of the test, with a risk estimation for the pregnancy, are sent to the patients by post within 10 days with a copy to the GP. Laboratory tests involve four gene probes (AF508, G551D, G542X, 621 + 1G > T), detecting 83.5% of CF carriers in our
population.
So far 44 pregnancies have been screened. 1 carrier has been detected in the maternal-testing group; her partner tested negative. 2 carriers were detected in the couple-testing group, and both partners tested negative. 1 partner in the couple-testing group declined the test and the maternal sample tested negative. 14 pregnancies were not included in the pilot study, for the following reasons: 1 patient aged 17 years declined the test, then requested termination, changed her mind, and delivered prematurely; 4 booked after 14 weeks for antenatal care; 7 requested termination for reasons unrelated to CF; and 2 patients miscarried before antenatal booking. Preliminary results from questionnaires and interview indicate that women have a positive attitude to CF carrier screening and to general practice as the preferred place for counselling and testing. There is no evidence at this stage that the procedure has caused excessive anxiety (Spielberger scale). Our study will be extended to other local general practices because we believe that general practice provides the ideal setting for very early pregnancy screening and general genetic counselling. Here it becomes an integral part of primary health care and permits assessment of the psychological impact of screening on patients, partners, and families. This is a valuable model for the closer integration of primary and secondary health-care services. This work is supported by the Wolfson Foundation and the North Western Regional Health Authority. Brooklands Medical Practice,
H.
J. HARRIS
Manchester
D. SCOTCHER
Department of Medical Genetics, St Mary’s Hospital, Manchester M13 OJH, UK
D. CRAUFURD A. WALLACE R. HARRIS
Mayall E, Chapple J, et al. Screening for carriers of cystic fibrosis through primary health care services. Br Med J 1991; 303: 504-07.
1. Watson EK,
Population screening for cystic fibrosis SIR,-We are involved in a pilot project of population screening for cystic fibrosis (CF) carriers, using mouthwash samples to screen for four mutations (AF508, G551D, G542X, 621 + 1G>T). We offered all members of staff in our division of molecular and medical genetics confidential screening for carrier status and report here the uptake of testing in this genetically interested and informed group of adults, predominantly of reproductive age. In December, 1991, three posters advertising the availability of confidential screening were displayed prominently, giving two contact names (a clinical geneticist and a nurse genetics counsellor). Those requesting screening were given an information leaflet (devised for our population screening programme) and then interviewed privately to establish whether there was a family history of CF, to check that they understood the inheritance of CF, and to confirm that neither they, their partner, nor anyone else in their family were pregnant. We also reminded them that a negative test result would reduce their carrier risk (to 1 in 130 for caucasians), but not eliminate it. Each mouthwash sample was given a coded reference number, the identity being known only to the clinicians offering the service. The results were handed to staff members personally one week later, together with a copy for them to pass on to their general practitioner. There are 110 members of staff in the division, of whom 80 are female (73%). 18 requested screening during the first three days, and 5 more presented a month later, while being screened for hepatitis B immunity status, when a personal verbal offer of CF screening was made. Of the 23 staff requesting screening, 20 were female (87%). 1 female had her test postponed because a relative was in late pregnancy at that time. The uptake rate for CF carrier screening was therefore about 20%. No carriers were detected.
