Cystic fibrosis should be added to diseases sought in all newborn babies

EDITOR—Wald and Morris's editorial on neonatal screening for cystic fibrosis is a good example of the different viewpoints held by doctors concerned with public health and by clinicians and highlights the need for both groups to have input into health service policy.1 They reviewed papers describing nutritional benefits of neonatal diagnosis of cystic fibrosis 2 3 with extrapolations predicting long term individual health benefits and short to medium term costs of a screening programme. The differences between screened and unscreened patients were small in terms of growth during the first 10 years. Healthcare purchasers are more easily persuaded by short term financial arguments than by long term predictions, particularly when the predictions involve many uncertainties, but clinicians can advance other persuasive arguments in favour of screening newborn babies.

Firstly, for parents to be confronted with the diagnosis of cystic fibrosis in their baby is always unpleasant. The shock can be mitigated by the knowledge that the diagnosis was made early, perhaps even before symptoms were noted; that attempts will be made to prevent or minimise lung damage; and that a programme of expert care is being offered. In contrast, many parents describe feelings of anger and mistrust when the diagnosis has been delayed and when irreversible lung damage—which may or may not have been preventable—has already occurred. It is in the interests of all, particularly the affected child, that complete confidence should exist between the doctor and the parents, who must deliver most of the care.

Secondly, the prognosis for cystic fibrosis is steadily improving4 and there are real prospects that effective, if not curative, treatment based on an understanding of the pathophysiology of cystic fibrosis at the cellular level will be available before long.5 Children who will then derive most benefit will be those for whom treatment can be started before lung damage has occurred. We should not wait for this treatment to be announced before we start screening, because that would deprive a considerable cohort of children of its maximal benefits. Dankert-Roelse and te Meerman are right3: now that we have reliable methodology, screening for cystic fibrosis should be added to screening for phenylketonuria and hypothyroidism for all newborn babies.

Early diagnosis allows option of prenatal diagnosis in subsequent pregnancies

EDITOR—Like Wald and Morris, we do not advocate neonatal screening for cystic fibrosis, although the situation is not as simple as they seem to suggest. The benefits of screening are not limited to early treatment of affected children; early diagnosis allows parents to have the options of prenatal diagnosis in subsequent pregnancies, although only a minority of carrier couples can be detected in this way.

Data from the confidential inquiry into counselling for genetic disorders confirm that delay in the diagnosis of cystic fibrosis is an important factor in the birth of a subsequent affected child. We know of 68 second affected children born between 1991 and 1995. For 22 of these the delay in the diagnosis of cystic fibrosis in the first child was stated to have led to the birth of the second affected child. The median delay in diagnosis after the birth of the first child with cystic fibrosis was 38 (range 17-96) months. Although families with two affected siblings from separate pregnancies are a highly selected group in which other causative factors may be concentrated, this is to some extent balanced by families with two affected children in which the diagnosis has yet to be made.

Early diagnosis is important to parents even if it makes little difference to outcome

EDITOR—Wald and Morris have rightly cautioned1 against accepting at face value an enthusiastic interpretation2 of the recent results of the Wisconsin trial of screening for cystic fibrosis.3 Despite its attractively simple design, this is not an easy study to interpret: the screening method was changed part way through to one of “greater sensitivity and specificity”3; follow up of cases found to be positive on screening to produce the “early diagnosis” group was quite leisurely by United Kingdom standards; and, as Wald and Morris point out, the four year blind period effectively precludes analysis of short term benefits. Wald and Morris may, though, present too negative a message. The subtitle to their editorial—“no evidence yet of any benefit”—suggests an excessively austere approach to what may be allowed as a benefit, while their statement in the opening paragraph that “early knowledge of a serious disorder will cause more harm than good if there is no effective remedy” is not supported by the available evidence.

The NHS Executive Health Technology Assessment Programme recently commissioned two studies of neonatal metabolic screening. The brief included gathering and using information on the psychological and social impact of neonatal screening, including acceptability to patients. For the psychological section of the Sheffield based study4 two of my colleagues (P Nicholson and J R Tawnily) examined 758 papers found by systematic search of the literature and identified 57 of sufficient relevance and quality for detailed review. They concluded that there is considerable evidence of parental support for diagnosis based on screening, even for diseases such as Duchenne muscular dystrophy for which there is no effective treatment, and no evidence that diagnosis through screening produces greater distress overall than diagnosis by conventional methods. These findings support the general clinical observation that early diagnosis is important to parents even if it makes little difference to outcome.5

Roughly seven tenths of infants with cystic fibrosis are symptomatic by 6 weeks of age. Many suffer significant malnutrition before diagnosis, and parents may become involved in a distressing diagnostic odyssey. Neonatal screening can be seen as an obvious step in the general movement towards the earlier and more effective treatment of cystic fibrosis. Evidence for improved long term outlook is fragmentary, but this should not lead us to ignore the more immediate and tangible benefits of systematic early diagnosis.