We read with interest the letter by Thayyil-Sudhan and Gupta[1]
reporting their study on the role of dipsticks in the detection of urinary
tract infection in children. We believe that this is a very important
subject and wish to comment on the report and their conclusions in the
light of our published study.[2]
We note that 188 urines were not sent for culture, it is not therefore
possible to d...
We read with interest the letter by Thayyil-Sudhan and Gupta[1]
reporting their study on the role of dipsticks in the detection of urinary
tract infection in children. We believe that this is a very important
subject and wish to comment on the report and their conclusions in the
light of our published study.[2]
We note that 188 urines were not sent for culture, it is not therefore
possible to determine the number of true and false negative dipstick tests
(if any). Without these data, calculation of sensitivity and specificity
of dipstick testing becomes impossible.[3] Because of the above we
believe that the data presented are skewed secondary to a flawed
experimental design. As a consequence of this, the statement of the
authors that "UTI in children cannot be excluded by a negative nitrite or
leukocyte esterase reaction" is difficult to justify.
There is no information to indicate whether children who were on
antibiotic therapy at or immediately prior to admission were included in
the study. If this is the case the possibility of false negative culture
results cannot be excluded and this will add further bias to the results.
No data are provided about the number of infants included in the study.
It has been reported that negative dipstick tests has a higher false
negative rate in infants or in cases of urinary frequency because
decreased bladder incubation time diminishes in-vivo bacterial
multiplication.[4] We are not told about the percentage of the samples,
which were collected by pads compared to mid-stream specimens as this may
further add to the inaccuracy of the culture results.
In our prospective study[2] on 325 children in whom UTI was a possibility
on clinical grounds all urines were sent for laboratory examination. The
laboratory was unaware of the results of the dipstick tests until the end
of the study. Analysis of our data showed that the combination of
negative dipstick tests for nitrite and leucocyte esterase gave a negative
predictive value for UTI of 96.9%, with a specificity of 98.7%. The
figures for infants were 96.7% and 99.2% respectively. A positive nitrite
and/or leucocyte esterase had a positive predictive value of 60.0% and a
sensitivity of 54.6%, compared to 50.0% and 20.0% respectively in
infants. In our series we found that there were four false negative and
six false positive nitrite tests.
The dipstick tests are most likely to be useful as a screening test to
exclude UTI in children but may be less suitable for infants. It should
not be used to diagnose urinary tract infection. We therefore disagree
with Thayyil-Sudan and Gupta in their view that “if nitrites are positive
empirical treatment or UTI seems to be reasonable until cultures are
positive”.
References
(1) Thayyil-Sudhan S, Gupta S. Dipstick examination for urinary tract
infections [letter]. Arch Dis Child 2000;82:271-2.
(2) Sharief N, Hameed M, Petts D. Use of rapid dipstick tests to exlude
urinary tract infection in children. Br J Biomed Sci 1998;55:242-6.
(3) Lohr JA. Use of routine urinalysis in making a presumptive diagnosis
of urinary tract in children. Pediatr Infect Dis J 1991;10: 646–50.
(4) Hellerstein SL. Urinary tract infections: Old and new concepts. Ped Clin N Am 1995;42:1433–57.
How many times do general practitioners here parents say "I do not want my baby vaccinated"? Quite often, I guess. As vaccine uptake rates are
maintained at high levels, notifications of the diseases prevented by them
have fallen. As the incidence of these diseases have fallen from the
public consciousness, public attention has deviated from these nasty
diseases to its side effects. The paper from Go...
How many times do general practitioners here parents say "I do not want my baby vaccinated"? Quite often, I guess. As vaccine uptake rates are
maintained at high levels, notifications of the diseases prevented by them
have fallen. As the incidence of these diseases have fallen from the
public consciousness, public attention has deviated from these nasty
diseases to its side effects. The paper from Gold M et al[1] is a reminder
to health professionals that vaccination schedules can be safely carried
on in spite of most adverse reactions.
Some districts, including ours, run immunisation helplines for
primary healthcare teams.[2] The most common query we get is from the practice
nurse when a mother presents with the child for the next dose of DPT, Hib, and
meningitis C vaccine and reports a severe local reaction or prolonged crying
after the previous dose. What we find time and time again is that parents
seldom go to their general practitioner immediately. An opportunity
to check the reaction out and make clear and careful decisions about the
future is lost. It is debatable how reliable or vivid parental accounts of
a swelling or length and quality of crying could be a month later. We did
not find any reference as to how well the yellow card system of reporting
adverse immunisation reactions is used in the UK.
A report from the US[3]
does suggest that their counterpart to the yellow card (VAERS) may not be
reliable. In light of the paper by Gold et al[1] and our experience we have the following
suggestions to make:
1. Practice nurses and general practioners should encourage parents to bring the
child back if they are worried about side effects
2. The yellow card system of reporting adverse drug reactions should
be used appropriately
3. Health professionals should seek expert advice before not
recommending any vaccine
4. There are very few true vaccine side effects. The Green Book[4] in
the UK should reflect the increasing evidence of vaccine safety. This can
help boost professional and parental confidence in vaccination programmes.
Dr Ashok Nathwani
Consultant Paediatrician
Portsmouth, UK
References
(1) Gold M, Goodwin H, Botham S, Burgess M, Nash, Kempe A. Re-vaccination of 421 children with past history of an adverse vaccine reaction in a special immunisation service. Arch Dis Child 2000;83:128-31.
(2) Finlay F, McKechnie L, Pearce A, Lenton S. Immunisation telephone hotline audit. Ambulatory Child Health 1999;5:295-302.
(3) Braun MM, et al. Report of a US Public Service workshop on Hypotonic Hyporesponsive Episode (HHE) after pertussis immunisation. Pediatrics 1998;102:e52.
(4) Immunisation against Infectious Disease. London: HMSO, 1996.
I read with interest the article on Imaging the Less Seriously Head
Injured Child.[1]
The authors state that bruising with a yellow hue suggests that
injury occurred at least 48 hours earlier. Unfortunately this statement
is not referenced and the main articles I am aware of on the age and
colour of bruising are those of Stevenson and Bialas published in ADC in 1996,[2] Schwartz & Ricci, 1996,...
I read with interest the article on Imaging the Less Seriously Head
Injured Child.[1]
The authors state that bruising with a yellow hue suggests that
injury occurred at least 48 hours earlier. Unfortunately this statement
is not referenced and the main articles I am aware of on the age and
colour of bruising are those of Stevenson and Bialas published in ADC in 1996,[2] Schwartz & Ricci, 1996,[3] and Langlois and Gresham in 1991.[4]
Langlois and Gresham studied the colour changes of bruises with time
and from their study found it was only possible to conclude that a bruise
with a yellow colour was more than 18 hours old. The significance of the
appearance of other colours in terms of estimating the time of occurrence
was not helpful.
Stevenson and Bialas[2] also found that ageing of bruises was much
less precise than text books imply and found that green or yellow hues
suggested an injury to be at least 24 - 48 hours old. Shwartz & Ricci
concluded that the available literature does not permit the estimation of
a bruise's age with any precision based on colour.[3]
I should be grateful to know if Glasgow and McGovern found any
further research to assist them in ageing bruises as I make a particular
point in my teaching of Child Protection and the writing of medico/legal
reports to urge extreme caution on statements which specify the age of
injuries based on their colouring.
Dr L Light
References
(1) Glasgow JFT, McGovern SJ. Imaging the less seriously
head injured child. Arch Dis Child 2000;82:333-5.
(2) Stevenson T, Bialas Y. Estimation of the age of bruising. Arch Dis Child 1996;74:53-5.
(3) Schwartz AJ, Ricci L. How accurately can bruises be aged
in abused children? Literature review and synthesis. Pediatrics 1996;97:254-7.
(4) Langlois NET, Gresham GA. The ageing of bruises: a
review and study of the colour changes with time. Forensic Sci Int 1991;50:227-38.
Stewart-Brown's paper on the compatibility of medical practice
in community paediatrics with that in public health[1] is a superlative
effort. This is more so as it has come at a time when community paediatrics
is being actively discussed by the RCPCH (UK Royal College of Paediatrics and Child Health) for a variety of reasons but,
perhaps, most importantly because it does not seem to attract enough...
Stewart-Brown's paper on the compatibility of medical practice
in community paediatrics with that in public health[1] is a superlative
effort. This is more so as it has come at a time when community paediatrics
is being actively discussed by the RCPCH (UK Royal College of Paediatrics and Child Health) for a variety of reasons but,
perhaps, most importantly because it does not seem to attract enough
specialist registrars.
It can be argued that all paediatricians (just not
community paediatricians) can and do play an important role in child
advocacy issues at various levels. From the clinical perspective the
community paediatric role in immunisation and child health surveillance is
the most important.
Trainees in paediatrics need to recognize that child public health is
a small (albeit important) role of the community paediatricians. The bulk
of community paediatricians are neurodevelopmental specialists. Many have
an important role in child protection. Some community paediatricians are
developing a behavioural paediatric interest in their clinical practice.
Most districts in the UK need their community paediatricians to look after
families with children with disabilities. Some districts (like ours) need
them to offer outpatient epilepsy services as well. With increasing
prevalence of behavioural problems in children, many community
paediatricians have trained (or retrained) themselves to cater to this
need. Useful links with child psychiatric and psychology colleagues have
been forged. In fact, our counterparts in the US are called developmental
and behavioural paediatricians and their core curriculum reflects the depth
of training offered for both these domains.[2]
There is no doubt, therefore,
that the term “community paediatrics” is a misnomer and may not offer
confidence to the budding specialist registrar who may find being a
neurologist or an oncologist a better bet. There is increasing specialism
within community paediatrics, and the job title needs to reflect that
expertise.
It is very possible that a small minority of (community)
paediatricians may chose to train with a major public health interest. It
may be helpful to know that the American Acdemy of Pediatrics has a
section for paediatricians with this interest.[2] The bulk should continue
(to train and practice) with a major clinical interest and that should be
an important selling point for community paediatrics. Hopefully job titles
in the future will reflect the clinical expertise. This will not only help
trainees but also purchasers, referers and the families we serve.
This letter is not meant to be in any way critical of Dr Stewart-Brown’s paper which, in fact has highlighted the importance of public
health medicine for (community) paediatricians. Health promotion is indeed
a skill that can be applicable easily in clinical practice.
Dr Ashok Nathwani
Consultant (Community) Paediatrician
Portsmouth, UK
References
(1) Stewart-Brown S. Is the ethos of medical practice in community paediatrics compatible with that in public health? Arch Dis Child 2000;83:101-3.
(2) Section on Community Pediatrics, American Acdemy of Pediatrics, http://www.aap.org/commpeds/ [accessed 3 Aug 2000].
Dr Mitchell is concerned that the methodology used in our study does
not simulate the release of aerosol from a metered dose inhaler (MDI). As
discussed in the article, the method of aerosol delivery in our study
differs from that of a MDI but as the delivery system was kept constant
and the particular spacer varied, a valid comparison of the efficacy of
different spacers could be made.[1] This deli...
Dr Mitchell is concerned that the methodology used in our study does
not simulate the release of aerosol from a metered dose inhaler (MDI). As
discussed in the article, the method of aerosol delivery in our study
differs from that of a MDI but as the delivery system was kept constant
and the particular spacer varied, a valid comparison of the efficacy of
different spacers could be made.[1] This delivery system has been
previously developed and tested in older children.[2] In these studies
aerosol lung deposition was equivalent from a conventional spacer or
sealed modified bottle spacer but a cup performed poorly delivering
significantly less aerosol to the lungs than did the other spacers.
The validity of these findings was borne out by the results of a
clinical study in which a similar response to bronchodilator was obtained
when children with acute asthma were given a beta-2 agonist via an MDI-
bottle or conventional spacer but a poor response occurred in those using
a cup.[3]
We agree with Dr Mitchell that the presence of an inhalation valve
may affect pulmonary deposition of aerosol. However, valveless spacers
may also function efficiently as spacers. When compared to an MDI alone,
increased lung deposition has been reported with a valved Cone Spacer and
a valveless Tube Spacer.[4] These two spacers have also been found to
produce similar increases in bronchodilation compared to a MDI alone.[3]
Moreover, oropharyngeal deposition may be reduced by up to 60% with a
valveless spacer.[4] Recently, valveless spacers have been reported to
enhance the delivery of aerosol to the lungs in infants with chronic lung
disease compared to the same spacer with a valve.[5] The results of our
clinical study suggest that a valveless bottle spacer provided effective
drug delivery to the lungs resulting in similar bronchodilation compared
to that obtained with a valved conventional spacer.[6]
The availability of a spacer device is essential in order to provide
care to children with asthma. For many children particularly those in
developing countries, a low cost spacer is not available. We believe that
our studies have shown that a modified 500ml plastic bottle functions
effectively as a spacer providing equivalent or superior aerosol
deposition to a conventional spacer and producing similar clinical
improvement. Such a bottle-spacer is a first step in providing asthma
care to many children throughout the world.
Heather J Zar
Michael Mann
Eugene Weinberg
Department of Paediatrics and Child Health
Red Cross Children's Hospital
University of Cape Town, South Africa
References
(1) Zar HJ, Weinberg EG, Binns HJ, Gallie F, Mann MD. Lung
deposition of aerosol - a comparison of different spacers. Arch Dis Child
2000;82:495-8
(2) Zar HJ, Liebenberg M, Weinberg E, Binns HJ, Mann MD. The efficacy
of alternative spacer devices for delivery of aerosol therapy to children
with asthma. Ann Trop Paed 1998:18;75-9
(3) Rivlin J, Mindorff C, Reilly PA, Levison H. Pulmonary response
to a bronchodilator delivered from three inhalation devices. J Pediatr
1984;104:470-3
(4) Newman SP, Moren F, Pavia D, et al. Deposition of pressurized
suspension aerosols inhaled through extension devices. Am Rev Respir Dis
1981;124:317-20
(5) Fok TF, Lam K, Chan CK et al. Aerosol delivery to non-ventilated
infants by metered dose inhaler: Should a valved spacer be used? Pediatr
Pulmonol 1997:24;204-212
(6) Zar HJ, Brown G, Donson H, Brathwaite N, Mann MD, Weinberg EG.
Home-made spacers for bronchodilator therapy in children with acute
asthma: a randomised trial. Lancet 1999:354;979-82.
Poustie et al state that there is no computer package available in the United Kingdom
for calculating percentage weight for height (%WFH). This is incorrect
and for many years there has been available just such a package entitled
W4H under the copyright of Great Ormond Street Hospital for Children NHS
Trust. The program can be used on any version of Windows from 3.1
onwards, Excel, and on Psion's. This p...
Poustie et al state that there is no computer package available in the United Kingdom
for calculating percentage weight for height (%WFH). This is incorrect
and for many years there has been available just such a package entitled
W4H under the copyright of Great Ormond Street Hospital for Children NHS
Trust. The program can be used on any version of Windows from 3.1
onwards, Excel, and on Psion's. This program was produced by the Eating
Disorders Research Team at Great Ormond Street but can be purchased from
the address below:
Dr Bryan Lask
Child and Adolescent Eating Disorders Research Team
Department of Psychiatry
Jenner Wing, St George's Hospital Medical School
London SW17 0RE, UK
As I understand the Scientific Method, a statement purporting to be
factual, either in a scientific article or in a discussion with peers,
must be supported by cited evidence that may be publicly examined for its
scientific veracity.
The paper by Heeley et al provides data to illustrate the equivalence of
conductivity and chloride in cystic fibrosis (CF)
diagnosis,[1] and therefore corrob...
As I understand the Scientific Method, a statement purporting to be
factual, either in a scientific article or in a discussion with peers,
must be supported by cited evidence that may be publicly examined for its
scientific veracity.
The paper by Heeley et al provides data to illustrate the equivalence of
conductivity and chloride in cystic fibrosis (CF)
diagnosis,[1] and therefore corroborates the
findings of an earlier clinical trial by Hammond et al.[2] Further, a
statistical comparison of the extensive published sweat chloride data of
Shwachman et al[3] with the conductivity data of Hammond et al shows that the two
are of equal discriminatory power in CF diagnosis.
Despite this evidence, LeGrys has written a document[4] that
contains a number of assertions on this subject and on other aspects of
sweat testing, that are not supported by any published results of original
work of which I am aware. No clinical trial data exist which show that
conductivity should only be used as a screen, that it is in any way
inferior to chloride as a reliable diagnostic discriminator, or that
conductivity readings of 50 mmol/L are positive for CF. LeGrys's call
for more studies on this matter may be seen as an evasion of the true
issue.[5] I suggest that the time has come, albeit belatedly, for her to
substantiate her case, not with opinions, but by providing proper
citations for relevant experimentally-obtained data to support her
contentions in the said document.
In a separate article[6] LeGrys refers to conductivity as a
"qualitative" assay, appearing to infer that it is less reliable than
chloride analysis. The term "quantitative", used in the pad-absorption
method merely indicates that gravimetric means are used to measure the
obtained sweat. It is obvious that this must be done to allow measurement
of chloride concentration since elution of collecting pads is involved.
The conductivity method is unequivocally quantitative because it measures
a solution property in a micro-cell of defined geometry. The inference is
therfore absurd and irrelevant.
LeGrys, in her eLetter,[5] makes the incredible statement that
since sodium is not as reliable as chloride as a discriminator it would
seem "logical" (sic) that because conductivity measures both, the
discriminatory advantage of chloride would be cancelled out. The logic of
this is difficult to comprehend. Increase in sweat chloride due to
functional aberration of the chloride channel must be compensated by
increase of one or another of the available cation species eg, potassium,
sodium or ammonium in order to satisfy the Law of Electrical Equivalence.
Such an increase in chloride will therefore be reflected by a
proportionate increase in the total electrolyte concentration, which is
the basis of analysis by electrical conductivity.
It is regrettable that lack of proper attention to basic scientific
principles has persisted in the NCCLS Guidelines for sweat testing for a
considerable time without correction and has produced increasing confusion
among medical technologists, particularly in the United States. It is
sincerely hoped that the author of this document will see fit to amend it
appropriately by substituting scientific accuracy for prejudice.
References
(1) Heeley ME, Woolf DA, Heeley AF. Indirect measurements of sweat electrolyte concentration in the laboratory diagnosis of cystic fibrosis. Arch Dis Child 2000;82:420-4.
(2) Hammond KB, Turcios NL, Gibson LE. Clinical evaluation of the
macroduct sweat collection system and conductivity analyser in the
diagnosis of cystic fibrosis. J Pediatr 1994;124:255-60.
(3) Webster HL. Sweat conductivity is a valid analysis for cystic
fibrosis diagnosis. Proceedings of the International Conference; Neonatal
Screening for Cystic Fibrosis. Caen, Sept. 10-11, 1998:101-5
(4) Sweat Testing: Sample collection and Quantitative Analysis:
Approved Guideline. National Committee for Clinical Laboratory Standards
(NCCLS) Document C34-A, 1994.
(5) LeGrys VA. Sweat chloride and conductivity. Arch Dis Child [Rapid Response] 17 July 2000.
(6) LeGrys VA. Sweat Testing for the Diagnosis of Cystic Fibrosis; Practical Considerations. J Pediatr 1996;129:892-7.
Cappendijk and Hazebroek (Arch Dis Child 2000;83:64-6) conclude from
their data that "the major factor in delay is suspected gastroenteritis".
Other studies have not given this factor such prominence and the study
population suggests that the Sophia Hospital was acting as a referral
centre: 32 of 78 children whose admission was delayed for 48 hours had
been seen first by a paediatrician, which may i...
Cappendijk and Hazebroek (Arch Dis Child 2000;83:64-6) conclude from
their data that "the major factor in delay is suspected gastroenteritis".
Other studies have not given this factor such prominence and the study
population suggests that the Sophia Hospital was acting as a referral
centre: 32 of 78 children whose admission was delayed for 48 hours had
been seen first by a paediatrician, which may increase the numbers with
suspected gastroenteritis.
In seeking the chief causes of delayed diagnosis it is helpful to
study all children referred to a district hospital from its catchment
area. Jackson in Newcastle found that parental delay over consulting the
family doctor was important and then, in nearly one-third of 311 home
visits, the practitioner did not decide until a second visit that
admission to hospital for ?acute appendicitis was needed.[1] Jackson, a
paediatrician, did not identify gastroenteritis as a factor. Other work
confirms these findings.[2]
In Aberdeen over 300 children are admitted annually from our region
with acute abdominal pain, and have been studied prospectively since 1965.[3, 4] This soon revealed that about one-third had acute appendicitis, one-third progressively settled without treatment (acute non-specific
abdominal pain, or NSAP) and others had medical and surgical conditions.
Among one year's admissions we found that 20 (18%) of 114 children with
proven acute appendicitis complained of diarrhoea compared with 9% of 119
children with NSAP. Of the 20, 15 had rectal tenderness and proved to have
pelvic appendicitis or peritonitis: we emphasised the importance of
identifying, among the many children with gastroenteritis seen by family
doctors, the few who also complain of abdominal pain, who require careful
abdominal and rectal examination.[3] The practice of "Active Observation"
encourages this.[4]
Occasionally delay in diagnosis of appendicitis is seen by the
surgeon on a call to the
isolation ward, where a child has been mistakenly sent in with suspected
gastroenteritis, but this has not, over the years, been a major problem.
Peter F Jones Emeritus Clinical Professor of Surgery University of Aberdeen, UK
References
(1) Jackson RH. Parents, family doctors and acute appendicitis in childhood. BMJ 1963;ii:277- 81.
(2) Moss JG, Barrie JL, Gunn AA. Delay in surgery for acute appendicitis. J R Coll Surg Edin 1985;30:290-3.
(3) Winsey HS, Jones PF. Acute abdominal pain in childhood: analysis of a year's admissions. BMJ 1967;i:653-5.
(4) Driver CP, Youngson GG. Acute abdominal pain in children: a 25-year comparison. Health Bulletin 1995;53:167-72.
Michael Perkin[1] is absolutely right. The initial protocol defined
routine growth monitoring in the setting familiar to us in poorer
countries as three monthly measurements. As we found so few studies in our
first search, we extended the inclusion criteria to any trial where growth
is routinely monitored twice or more in any two year period in children
aged 0-5 years, but neglected to change the wording in t...
Michael Perkin[1] is absolutely right. The initial protocol defined
routine growth monitoring in the setting familiar to us in poorer
countries as three monthly measurements. As we found so few studies in our
first search, we extended the inclusion criteria to any trial where growth
is routinely monitored twice or more in any two year period in children
aged 0-5 years, but neglected to change the wording in the review. We
excluded "single measures at one age"-that is screening policies where all
children at a particular age are measured. However, assuming Hall[2] defines
growth monitoring as "at least two measures in the period 0 to 5 years" we then
sought trials in this area but found none. We thank Dr Perkin for pointing
this out, and will correct the inclusion strategy on the Cochrane Library,
and note the modification to the original protocol. He will note that even
with the wider definition we found no more trials, so the review remains
relevant to both poorer and richer countries.
We thank David Morley for his comments.[3] He notes we did not examine
whether health workers comprehend the growth chart. In fact, we sought
evidence that health workers understood charts and then took action by
seeking studies that recorded referrals (see inclusion criteria). One
study that met the inclusion criteria reported maternal comprehension
following targeted explanations, although it is not entirely clear what
the marks assigned in the test actually mean for the mother or infant. We
would advocate future research examines things that happen as a result of
growth monitoring, such as treatment of intercurrent illness or referral,
rather than what people comprehend about weight charts.
Paul Garner
Ratana Panpanich Stuart Logan
References
(1) Perkin M. Systematic review had no relevance to routine monitoring as it is undertaken in the UK. Arch Dis Child [Rapid Response] 20 May 2000
(2) Hall DMB. Growth monitoring. Arch Dis Child 2000;82:10- 15.
(3) Morley D. Growth monitoring. Arch Dis Child [Rapid Response] 17 July 2000
Zar and colleagues[1] compared home-made spacers and two commercially
available
valved holding chambers (VHCs) for the treatment of children with acute
asthma. We acknowledge that the practice of using empty drink bottles
is common in some countries (by either necessity or choice). We, as a
manufacturer of one of the VHCs that was evaluated, are highly concerned
about the support to the hypothesi...
Zar and colleagues[1] compared home-made spacers and two commercially
available
valved holding chambers (VHCs) for the treatment of children with acute
asthma. We acknowledge that the practice of using empty drink bottles
is common in some countries (by either necessity or choice). We, as a
manufacturer of one of the VHCs that was evaluated, are highly concerned
about the support to the hypothesis that coffee-cup or drink bottle
spacers are as effective as properly designed add-on devices, given by
implication in the Editor's comments on this article (Archives this Month June 2000),
In Zar et al's paper[1] the production technique did not simulate the
release of medication from a
pressurized metered dose inhaler (pMDI). Instead, the technique created
a radiolabelled aerosol by pneumatic nebulization into a bag (which would
have acted as a particle pre-selector). This set-up would not have
reproduced accurately the ballistic component (polydispersed particles)
that is inevitably released at actuation of a pMDI. It has already been
demonstrated that these particles are more effectively separated by a VHC
than a spacer (with no valve). Had a pMDI containing the radiolabelled
aerosol been used (as is the normal practice in gamma-scintigraphic
studies evaluating pMDI systems), we believe that the dynamic aerosol
behavior (inertial impaction of the ballistic component, turbulent
deposition, etc) following actuation into the chamber would have been
quite different to that observed by having patients drawing in the already
formed aerosol from an anesthesia bag. Simply put, the protocol more
closely simulated a continuous jet nebulizer releasing a liquid phase
aerosol into a bag, which was then connected to a chamber/spacer device,
and may therefore have little relevance to what actually occurs inside a
VHC used with a pMDI.
A well designed holding chamber (with a valve) will retain a
significant portion of the coarse component of the emitted dose (particles
greater than about 5 microns aerodynamic diameter) from the pMDI. A
spacer
(home-made or otherwise) will not perform this function effectively.
Rather it will momentarily contain the aerosol and then deliver particles
of all sizes to the well-coordinated patient who is able to time
inhalation with actuation of the pMDI. In the case of corticosteroid,
the emitted coarser particles can promote local topical infections, such
as oral candidiasis as well as increases in overall systemic absorption.
The inhalation valve, that distinguishes a VHC from a spacer,
needs to be a carefully designed component whose function is to retain the
aerosol once created following actuation of the pMDI, then release it
during the inspiratory cycle. Many children, particularly those
suffering an acute exacerbation of asthmatic symptoms, have poor
coordination, and are therefore likely to mistime inhalation with pMDI
actuation. Such patients, who are at greatest risk, are therefore likely
to derive least benefit from the use of home-made spacers.
While we have other observations of a technical nature, the
information given here should be sufficient to provide you with the
message that this study should not be taken as the final word but rather
as a finding concerning the debate about the efficacy of home-made versus
manufactured add-on delivery devices for use in pMDI-based therapy.
Having said this, if a VHC is unavailable for whatever reason, an empty
drinking bottle may be better than nothing at all.
Jolyon P Mitchell PhD, FRSC(UK), CChem
Scientific Director
Medical Aerosol Research Laboratory
Trudell Medical International
Reference
(1) Zar HJ, Weinberg EG, Binns HJ, Gallie F, Mann MD. Lung deposition of
aerosola comparison of different spacers. Arch Dis Child 2000;82:495-8.
Dear Editor:
We read with interest the letter by Thayyil-Sudhan and Gupta[1] reporting their study on the role of dipsticks in the detection of urinary tract infection in children. We believe that this is a very important subject and wish to comment on the report and their conclusions in the light of our published study.[2]
We note that 188 urines were not sent for culture, it is not therefore possible to d...
Dear Editor:
How many times do general practitioners here parents say "I do not want my baby vaccinated"? Quite often, I guess. As vaccine uptake rates are maintained at high levels, notifications of the diseases prevented by them have fallen. As the incidence of these diseases have fallen from the public consciousness, public attention has deviated from these nasty diseases to its side effects. The paper from Go...
I read with interest the article on Imaging the Less Seriously Head Injured Child.[1]
The authors state that bruising with a yellow hue suggests that injury occurred at least 48 hours earlier. Unfortunately this statement is not referenced and the main articles I am aware of on the age and colour of bruising are those of Stevenson and Bialas published in ADC in 1996,[2] Schwartz & Ricci, 1996,...
Dear Editor:
Stewart-Brown's paper on the compatibility of medical practice in community paediatrics with that in public health[1] is a superlative effort. This is more so as it has come at a time when community paediatrics is being actively discussed by the RCPCH (UK Royal College of Paediatrics and Child Health) for a variety of reasons but, perhaps, most importantly because it does not seem to attract enough...
Dear Editor
Dr Mitchell is concerned that the methodology used in our study does not simulate the release of aerosol from a metered dose inhaler (MDI). As discussed in the article, the method of aerosol delivery in our study differs from that of a MDI but as the delivery system was kept constant and the particular spacer varied, a valid comparison of the efficacy of different spacers could be made.[1] This deli...
Poustie et al state that there is no computer package available in the United Kingdom for calculating percentage weight for height (%WFH). This is incorrect and for many years there has been available just such a package entitled W4H under the copyright of Great Ormond Street Hospital for Children NHS Trust. The program can be used on any version of Windows from 3.1 onwards, Excel, and on Psion's. This p...
Dear Editor
As I understand the Scientific Method, a statement purporting to be factual, either in a scientific article or in a discussion with peers, must be supported by cited evidence that may be publicly examined for its scientific veracity.
The paper by Heeley et al provides data to illustrate the equivalence of conductivity and chloride in cystic fibrosis (CF) diagnosis,[1] and therefore corrob...
Dear Editor
Cappendijk and Hazebroek (Arch Dis Child 2000;83:64-6) conclude from their data that "the major factor in delay is suspected gastroenteritis". Other studies have not given this factor such prominence and the study population suggests that the Sophia Hospital was acting as a referral centre: 32 of 78 children whose admission was delayed for 48 hours had been seen first by a paediatrician, which may i...
Michael Perkin[1] is absolutely right. The initial protocol defined routine growth monitoring in the setting familiar to us in poorer countries as three monthly measurements. As we found so few studies in our first search, we extended the inclusion criteria to any trial where growth is routinely monitored twice or more in any two year period in children aged 0-5 years, but neglected to change the wording in t...
Dear Editor:
Zar and colleagues[1] compared home-made spacers and two commercially available valved holding chambers (VHCs) for the treatment of children with acute asthma. We acknowledge that the practice of using empty drink bottles is common in some countries (by either necessity or choice). We, as a manufacturer of one of the VHCs that was evaluated, are highly concerned about the support to the hypothesi...
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