Gabrielle J Laing, James Law, Abigail Levin, Stuart Logan
Laing G J, Law J, Levin A, Logan S.
Evaluation of a structured test and a parent led method for screening for speech and language problems: prospective population based study
BMJ 2002; 325 :1152
doi:10.1136/bmj.325.7373.1152
Early Identification of Speech and Language Disorders
Editor – in assessing the performance of potential screening methods,
Laing et al address an important issue regarding the early identification
of children with significant speech and language disorders (1). However we
feel that their conclusion that, ‘Screening is likely to be an ineffective
approach to the management of speech and language problems…’ is unduly
pessimistic given the study reported.
This study was undertaken in the context of the child health
surveillance programme, ‘a programme of care initiated and provided by
professionals, with the aim of preventing illness and promoting good
health’(2). The purpose of this programme is therefore screening (and
health promotion) rather than surveillance. In this context, any
investigation of the accuracy of a screening method needs to take into
consideration the performance of the current method, before reaching any
conclusions about its utility.
In the case of screening for speech and language disorders, there is
a paucity of evidence regarding the performance of the child health
surveillance programme as a method of detection of those children in need
of speech and language therapy services (SALTS). Data collected during the
Cambridge Language and Speech Project (3) has allowed us to investigate
the relationship between psychometric assessment of language (at 45
months) and SALTS referrals. The findings show that, even using a lenient
case definition (1.5 SD below the mean on any language test, without
reference to measures of non-verbal IQ) 20% of the non-cases had been seen
by SALTS. Furthermore 3% of those seen by SALTS had scored above the mean
on all language measures. At the same time, 14% of children meeting the
most stringent case criterion (ICD-10 criteria) had not been seen by SALTS
(unpublished).
These findings demonstrate that current practice is not targeting the
group of children who are most likely to benefit from SALTS intervention,
with both under-referral of children with, and over-referral of children
without, significant language difficulties.
A second concern about this study relates to the choice of case
definition. Application of the authors criteria for assigning case status
led to 21% and 29% of children being defined as having ‘severe language
disorder’ or being ‘in need of therapy’ respectively. The authors point
out, in their discussion, the possibility that their sample was biased in
favour of children with language difficulties. Inspection of the flow
chart for the study certainly supports this view. However, it is difficult
to accept that these biases can entirely account for this level of
prevalence given that a frequency of 2 – 8% would be expected at this age
(4).
Another explanation for the observed prevalence is that the norms for
the reference test do not apply to the population studied, resulting in
misclassification of non-cases as cases. If this occured randomly with
respect to performance on the screening instrument, the effect would be to
decrease sensitivity whilst leaving specificity largely unchanged. This
can therefore explain the observed finding in the present study of a low
sensitivity and high specificity when the reverse is more usually observed
in studies of screening for speech and language disorders (3, 4).
It is not difficult to make a case for early identification of speech
and language disorders. What is needed, however, is a randomised control
trial of the use of a systematic screening instrument compared to current
practice, with careful attention paid to choice of reference test on whose
basis diagnostic status is assigned.
1. Laing GJ, Law J, Levin A, Logan S. Evaluation of a structured test
and a parent led method for screening for speech and language problems.
British Medical Journal 2002;325:1152-1156.
2. Hall D, Hill P, Elliman D. The child surveillance handbook. Oxford:
Radcliffe Medical Press; 1994.
3. Stott CM, Merricks MJ, Bolton PF, Goodyer IM. Screening for Speech and
Language Disorders: the reliability, validity and accuracy of the General
Language Screen. International Journal of Language and Communication
Disorders 2002;37(2):133-151.
4. Law J, Boyle J, Harris F, Harkness A, Nye C. Screening for speech and
language delay: a systematic review of the literature. Health Technology
Assessment 1998;2(9):1-184.
Competing interests:
None declared
Competing interests: No competing interests