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Biomedical subjects

S A McKenzie

Publications and source records attributed to S A McKenzie.

At least 19 recordsLinked to original sources
PubMed2006

Linear growth and body mass index in pediatric patients with Cushing's disease or simple obesity.

BACKGROUND: Increasing prevalence of childhood obesity has resulted in an accelerating rate of referrals of overweight patients to pediatric clinics for exclusion of endocrine or metabolic etiologies. The exclusion of Cushing's disease (CD) requires complex and potentially invasive investigations. OBJECTIVE: To evaluate the sensitivity of accurate measurements of height, weight and body mass index (BMI) in discriminating between simple obesity and CD. METHODS AND PATIENTS: Height, weight and BMI were measured at diagnosis in 25 patients with CD; 14 males, 11 females, mean age 12.9 yr (6.4-17.8) and 41 patients with simple obesity (SO), defined as BMI >2.0 SD; 20 males, 21 females, mean age 9.4 yr (3.5-15.6). RESULTS: Mean (+/-SE) BMI SDS in the CD patients was 2.41+/-0.5 and in the SO patients 3.71+/-1.3. Height SDS in the CD patients was -1.88+/-0.24 and in the SO patients 1.18+/-0.19 (p<0.05). The mean (+/-SE) BMI SDS to height SDS ratio was significantly decreased in the CD compared with the SO patients; -1.81+/-0.54 vs +0.90+/-1.17 (p<0.0001). CONCLUSIONS: Simple, accurate measurement of height and BMI SDS values provides a quick, and sensitive diagnostic discriminator in pediatric patients with CD or SO, thus potentially avoiding complex investigations.

Adolescent↗
PubMed2005

A video questionnaire identifies upper airway abnormalities in preschool children with reported wheeze.

BACKGROUND: Accurate characterisation of subjects is essential to interpret data from studies investigating preschool wheezing. AIM: To assess whether a video questionnaire (VQ) identifies upper airway abnormalities in preschool children with reported wheeze. METHODS: Forty three children (median age 17 months, range 3-58) undergoing fibreoptic bronchoscopy for clinical investigation of troublesome noisy breathing at a tertiary centre were studied. Parents were shown a VQ with four clips (wheeze, stridor, and two other upper respiratory noises) and chose the clip(s) resembling their child's main symptom. Doctor observed symptoms, parental reported symptoms, and symptoms identified on VQ were related to bronchoscopy. RESULTS: Thirty subjects had wheeze as the main symptom: 19 had doctor observed wheeze (DOW) and 11 had parental reported wheeze (RW). Parents of two of the subjects with RW identified wheeze alone on VQ and both had normal bronchoscopic findings. Five of the remaining nine subjects with RW had upper airway abnormalities at bronchoscopy. Parents of six subjects with RW identified a noise other than wheeze on VQ; four of these had upper airway abnormalities. Parents of two subjects with RW did not identify a noise on VQ; one had upper airway abnormalities. Of the 19 with DOW, nine parents identified wheeze alone on VQ, and all had a normal upper airway. Parents of nine subjects with DOW identified a noise other than wheeze as an equal or only symptom, (no noise identified in one), and five had upper airway abnormalities. CONCLUSION: A VQ helps to identify upper airway abnormalities in preschool children with a history of wheezing.

Airway Obstruction↗
PubMed2005

Skin-prick testing as a diagnostic aid for childhood asthma.

Diagnosing asthma is problematic when based solely on reported symptoms. The purpose of this study was to evaluate skin-prick testing as a diagnostic aid for asthma in children. Skin-prick testing (SPT) was undertaken in children aged 2-10 years with either no history of wheeze (n = 149) or recent doctor-observed wheeze which responded to treatment with a bronchodilator, the "gold standard" (n = 164). Children with moderate or severe asthma were excluded. SPT positivity increased sharply at age 5 years in wheezers. Data were therefore divided into two age groups: 2- < 5 years (57 controls, 97 wheezers) and 5-10 years (92 controls, 67 wheezers). The sensitivity, specificity, and likelihood ratios of SPT positivity for wheeze were 32%, 89%, and 2.9, respectively, in the younger children, and 82%, 85%, and 5.5, respectively, in the older children. For a prevalence of 30% for asthma, the positive predictive values of a positive SPT were 55% and 70% for the younger and older age groups, respectively. The test characteristics of SPT for helping diagnose asthma in schoolchildren are good. The prevalence of wheeze in preschool children is high, and so SPT should be helpful even in this group. We suggest that clinicians consider skin-prick testing as a diagnostic aid for asthma.

Age Factors↗
PubMed2005

Diagnostic accuracy of bronchodilator responsiveness in wheezy children.

BACKGROUND: The aim of this study was to evaluate the diagnostic accuracy of bronchodilator responsiveness for asthma in 5-10 year old children. METHODS: Spirometric measurements were made in 142 children (58 wheezers) before and after 400 mug inhaled salbutamol. RESULTS: On a receiver operating characteristic curve, a 9% increase in predicted forced expiratory volume in 1 second was the cut off point that provided an acceptable balance of sensitivity and specificity for previous wheeze. This figure was 50% (95% CI 38 to 62) sensitive and 86% (95% CI 78 to 92) specific for detecting previous wheeze and multiplied the initial odds in favour of wheeze by a factor of 3.6 (95% CI 2.0 to 6.3). DISCUSSION: With an estimated pretest probability of wheeze of 10% in the community and 50% in a specialist clinic, the positive predictive values are 29% and 78%, respectively, for a 9% change. The value of bronchodilator responsiveness testing depends on the prevalence of wheeze in the population in which it is to be used.

Administration, Inhalation↗
PubMed2004

Airway resistance by the interrupter technique: which algorithm for measuring pressure?

Airway resistance using the interrupter technique (Rint) can be measured using commercial devices which employ different algorithms for estimating pressure change. We aim to describe differences in Rint due to algorithm. We compared Rint and change in Rint after bronchodilator, using four algorithms to estimate pressure change following interruption: 1) two-point back-extrapolation to interruption from points 70 msec and 30 msec from interruption, and similarly 2) to 15 msec from interruption, 3) at two-thirds from interruption, and 4) near end-interruption. Flow was measured immediately before interruption. Our subjects were 39 asymptomatic children 2-5 years old with previous intermittent wheeze. Rint differed significantly with algorithm. Geometric mean Rint (95% confidence interval (CI)) for algorithms 1-4 were 1.21 kPa x l(-1) x sec (1.18-1.24 kPa x l(-1) x sec), 1.31 kPa x l(-1) x sec (1.28-1.34 kPa x l(-1) x sec), 1.57 kPa x l(-1) x sec (1.54-1.61 kPa x l(-1) x sec) and 1.71 kPa x l(-1) x sec (1.67-1.75 kPa x l(-1) x sec), respectively. Measurement of change in R(int) following bronchodilator (BDR) did not differ on average with algorithm. Geometric means (95% CI) for BDR measurements for algorithms 1-4 were 29.9% (26.0-34.0%), 30.4% (26.4-34.5%), 32.9% (28.8-37.1%), and 31.7% (27.6-35.8%), respectively. However, measurement of change in individuals could differ by up to 40%, depending on algorithm. In conclusion, there are significant differences in Rint, depending on algorithm used to estimate pressure change. Measurement of change in Rint is unaffected on average, although in individuals there could be significant differences. Each laboratory should state its method and use the same algorithm for longitudinal and group data.

Airway Resistance↗
PubMed2003

Normative data for total serum immunoglobulin E measurements in children of three ethnicities.

BACKGROUND: It is about 20 years since IgE measurements were published for children without atopic disease. It is possible that the recent increase in atopic disease is reflected in altered measurements in subjects who have no clinical expression of atopy. If the measurement of IgE is to be used as a marker for atopy to characterize disease categories, contemporary normative data must be available. OBJECTIVE: To measure total serum IgE in healthy children of three ethnicities born and living in an inner city environment. METHODS: Subjects were aged 1 to < or = 12 years, of Afro-Caribbean, Bangladeshi and white British ethnicities, with no personal history of current atopic disease. An extra 1 mL of blood for the measurement of total serum IgE was collected when blood was taken for other purposes or when a surgical procedure was being undertaken. RESULTS: Measurements were taken from 151 boys (median age 5.4 years) and 106 girls (median age 6.0 years), who included 127 Bangladeshis, 58 Afro-Caribbeans and 72 white British children. Measurements increased with age but were not related to gender or ethnicity. The data were significantly higher than previous measurements by sixfold. CONCLUSION: These contemporary normative data allow the generation of z scores for total IgE measurements for clinical or epidemiological use.

Aging↗
PubMed2003

Repeatability of airway resistance measurements made using the interrupter technique.

BACKGROUND: To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms. METHODS: Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, three Rint measurements were made 15 minutes apart, before and after placebo and salbutamol given in random order. Results from those given placebo first were analysed for within-occasion repeatability. Between-occasion repeatability measurements were made 2-20 weeks apart (median 3 weeks). RESULTS: For 85 pairs of measurements before and after placebo the limits of agreement were 20% expected resistance and were unaffected by age or health status. The change in resistance following bronchodilator in one of 18 healthy children, 12 of 28 with cough, and 22 of 39 with wheeze exceeded this threshold. For between-occasion measurements the limits of agreement were 32% in 72 healthy subjects, 49% in 57 with cough, and 53% in 95 with previous wheeze. CONCLUSION: The measurement of airways resistance by the interrupter technique is clinically meaningful when change following an intervention such as the administration of bronchodilator is greater than its within-occasion repeatability. Between-occasion repeatability is too poor to judge change confidently.

Airway Resistance↗
PubMed2003

The use of corticosteroids in syntomathic asthma in childhood.

Corticosteroids (CS) have been used in the management of wheezing illnesses for several decades and have become the cornerstone of the management of childhood asthma. Inhaled corticosteroids are considered first-line treatment for frequent, persistent asthma in every guideline. Whilst undoubtedly they have provided enormous benefit to those asthmatics who would otherwise have been prescribed oral corticosteroids and so been at a high risk of side-effects, there is good evidence that inhaled corticosteroids are prescribed not only to too many asthmatic children but also to children who do not have asthma or who have other wheezing disorders. This review will assess the evidence for the benefit of corticosteroids, their use, and current prescribing practices in the common wheezing disorders of childhood.

Adrenal Cortex Hormones↗
PubMed2002

Airway resistance measured by the interrupter technique: normative data for 2-10 year olds of three ethnicities.

BACKGROUND AND AIMS: The measurement of airway resistance using the interrupter technique (R(int)) is feasible in preschool children and other subjects unable to undertake spirometry. This makes it potentially useful for the measurement of lung function in these groups. Commercial devices use different algorithms to measure pressure and flow from which R(int) is derived. This study provides normative values for British children using devices from a single manufacturer. METHODS: R(int) was measured in 236 healthy children of three ethnic groups (Afro-Caribbean and black African, Bangladeshi, and white British) aged 2-10 years using Micro Medical devices. Software in the devices calculated R(int) from pressure measured by the two point, back extrapolation method from the pressure transient during valve closure, with flow measured just before valve closure. RESULTS: R(int) is related to both age and height, but when age is allowed for there is not a significant relation with height. Neither gender nor any of the ethnicities studied was significantly related to R(int). DISCUSSION: These measurements in healthy children using this technique may be used as reference data for similar populations.

Aging↗
PubMed2002

Difficult asthma in children.

Asthmatic children on high dose corticosteroids need to be fully assessed to ensure that such dosages are really necessary. Further work needs to be undertaken to find the best approach to poor treatment adherence and false claims for financial support. The benefits of particular components of specialist assessment need to be evaluated prospectively and multicentre collaboration is needed to evaluate phenotype specific treatment and new treatments for truly difficult asthma.

Adrenal Cortex Hormones↗
PubMed2001

Difficult asthma: defining the problems.

A retrospective survey was undertaken of children with difficult asthma, attending a respiratory clinic. The clinical and laboratory profiles of asthmatic children who were poorly controlled on > or = 800 microg of inhaled corticosteroids (ICS) were studied and compared to children well-controlled on > or = 800 microg ICS. Assessments were made of atopy, growth, lung function, treatment adherence, home environment, and responsiveness to corticosteroids (CS). Fiftyseven "difficult" and 23 well-controlled children were studied. Significant differences in the home environment were identified. Smoking was significantly more common in the difficult-to-control group. Nine children had alternative diagnoses. Poor CS responsiveness was present in 10 children. Adverse home environments, poor treatment supervision, alternative diagnoses, and unresponsiveness to CS were the most important factors in difficult asthma. A full assessment, including bronchoscopy, is indicated to avoid unnecessary increases in CS to doses that could cause side-effects.

Administration, Inhalation↗
PubMed2001

Lung function tests for pre-school children.

There are a few devices for measuring lung function in pre-school children. Neither the interrupter technique nor the forced oscillation techniques have been standardised. We highlight some of the issues around the measurement of airway resistance using the interrupter technique and emphasise that, as with other lung function measurements, operators should have a proper understanding of the methods before they can be applied. Both methods for measuring airway resistance have potential for clinical and research application.

Airway Resistance↗
PubMed2001

Parents' interpretations of children's respiratory symptoms on video.

AIMS: To investigate how parents report children's respiratory sounds on video compared to a clinical "gold standard". METHODS: Five clinicians agreed on 10 video clips of children with audible breathing. These responses were the "gold standard". The clips were shown to parents of children: (a) with asthma/wheeze; (b) with other respiratory complaints; (c) without respiratory complaints. Parents were asked what they called the sounds, where they originated, and whether their own child made similar sounds. RESULTS: A total of 190 parents took part. The "correct" labelling of wheeze was 59% (95% confidence interval 52 to 66%) and 47% (95% confidence interval 40 to 54%) for other sounds (stridor, snoring, stertor). Parents were better at locating both sounds than labelling. There were no differences between subject groups. There were more false positive responses to labelling and locating other sounds than for wheeze (27% v 8% and 33% v 10%). CONCLUSION: Parents locate sounds better than describing them. At least 30% of all parents use other words for wheeze and 30% labelled other sounds as "wheeze". This could have important clinical implications.

Adult↗
PubMed2001

Safety and ethics of bronchoscopy and endobronchial biopsy in difficult asthma.

AIM: To investigate the safety of bronchoscopy and endobronchial biopsy in children with difficult asthma, and discuss the ethical issues associated with the procedure. METHODS: A three year prospective observational study was performed in two tertiary paediatric respiratory centres specialising in the management of children with difficult asthma. A total of 48 children with difficult asthma and 35 non-asthmatic children were studied. RESULTS: Flexible bronchoscopy was performed under general anaesthesia in 38 children with difficult asthma, and rigid bronchoscopy was performed in 10, following a two week course of prednisolone. Endobronchial biopsy was performed in 47 patients. Perioperative complications occurred in one asthmatic undergoing flexible bronchoscopy (desaturation) and in two undergoing rigid bronchoscopy (desaturation in one, and bronchospasm and desaturation in one). There were no cases of significant bleeding or pneumothorax among the asthmatics. Flexible bronchoscopy was performed in 35 non-asthmatic patients with a variety of clinical indications. The total number of perioperative complications was greater in the non-asthmatics undergoing flexible bronchoscopy than in the asthmatics (17 complications in 35 children versus one in 38). Fever requiring hospital admission was documented in two asthmatics following bronchoscopy. Four asthmatics reported an increase in symptoms in the week following bronchoscopy. CONCLUSIONS: Bronchoscopy and endobronchial biopsy under general anaesthesia can be performed safely in children with difficult asthma, when the bronchoscopist and anaesthetist are suitably trained. The procedure is acceptable to the families involved.

Adolescent↗