Country-Wide Analysis of Systemic Factors Associated With Acute Ischemic Stroke Door to Needle Time.

Objective: Pre-hospital, in-hospital, and patient factors are associated with variation in door to needle (DTN) time in acute ischemic stroke (AIS). Publications are usually from large single centers or multicenter registries with less reporting on national results. Materials and methods: All AIS patients treated with intravenous tissue plasminogen activator (iv-tPA) over 4 years (2013-2016) in Northern Ireland were recorded prospectively, including patient demographics, pre-hospital care, thrombolysis rate, and DTN time. Logistic regression was performed to identify factors associated with DTN time. Results: One thousand two hundred and one patients from 10,556 stroke admissions (11.4%) were treated with iv-tPA. Median NIHSS was 10 (IQR 6-17). Median DTN time was 54 min (IQR 36-77) with 61% treated < 60 min from arrival at hospital. National thrombolysis numbers increased over time with improving DTN time (P = 0.002). Arrival method at hospital (ambulance OR 2.3 CI1.4-3.8) pre-alert from ambulance (pre-alert OR = 5.3 CI3.5-8.1) and time of day (out of hours, n = 650, OR 0.20 CI 0.22-0.38) all P < 0.001, were the independent factors in determining DTN time. Variation in DTN time between centers occurred but was unrelated to volume of stroke admissions. Conclusion: Ambulance transport with pre-hospital notification and time of day are associated with shorter DTN time on a national level. Most thrombolysis was delivered outside of normal working hours but these patients are more likely to experience treatment delays. Re-organization of stroke services at a whole system level with emphasis on pre-hospital care and design of stroke teams are required to improve quality and equitable care in AIS nationally.

Variabilidad de la respuesta plaquetaria a la aspirina / Assessing platelet response to aspirin

Introducción y objetivos: A pesar de que el estudio Antiplatelet Trialists' Collaboration demostró una reducción del 25% de los eventos mayores con el uso de aspirina en enfermos de alto riesgo, un porcentaje de pacientes presentan eventos isquémicos recurrentes. Esto ha llevado a la descripción de la "resistencia a la aspirina" con una tasa muy variable, de 0.4% a 83%. Este estudio evaluó la variabiliad en la función plaquetaria basal, la prevalencia de la resistencia a la aspirina, y la efectividad y reproducibilidad de los estudios de función plaquetaria. Materiales y métodos: Se llevó a cabo un estudio aleatorizado y cruzado de mediciones repetidas, con sujetos saludables de entre 18 y 60 años. Luego de firmar el consentimiento informado, los pacientes fueron distribuidos en forma aleatorizada a recibir aspirina en dosis de 75 mg o 300 mg; fueron evaluados al inicio y luego de cuatro períodos de tres semanas mediante diferentes técnicas: Optical Platelet Aggregation (OPA), PFA-100™, VerifyNow™, y los niveles séricos y urinarios de tromboxano B2 (TXB2). Se obtuvo la aprobación del comité de ética local. El análisis estadístico fue realizado con el programa SPSS17. Resultados: El índice global de resistencia a la aspirina fue variable, entre 2.4% y 63.5% en función de la técnica utilizada. Se demostró una variabilidad interindividual e intraindividual significativa al inicio y con la administración de placebo en las diferentes técnicas. La sensibilidad de los ensayos varió entre 24% (OPA ADP10) y 87.8% (tromboxano sérico), y la especificidad varió entre 81% (PFA-100™) y 97.4% (tromboxano). La selección de "valores de corte" alternativos provocó tasas de prevalencia diferentes de resistencia bioquímica a la aspirina, con un mecanismo de compensación entre la sensibilidad y la especificidad. Conclusiones: La respuesta a la aspirina mostró una marcada variabilidad interensayo, interindividual y temporal. Se requieren varias evaluaciones con diferentes técnicas para diagnosticar en forma confiable la resistencia a la aspirina. La selección de valores discriminativos alternativos debería considerarse al evaluar formalmente esta entidad

Introduction: Despite the 25% reduction in major events with aspirin in high-risk patients reported by the Antiplatelet Trialists' Collaboration, a proportion of patients develop recurrent ischaemic events. This has led to the emergence of 'aspirin resistance' with rates between 0.4% and 83% reported. This study assessed variability in baseline platelet function, prevalence of aspirin resistance, and the performance and reproducibility of platelet function testing methods. Materials and Methods: A repeated-measures randomised crossover study was performed in healthy individuals aged 18-60 years. After informed consent, patients were randomised to aspirin dose (75 mg or 300 mg) and treatment sequence with testing at baseline and after each four 3-week treatment period via Optical Platelet Aggregation (OPA), PFA-100™, VerifyNow™, and serum and urinary thromboxane (TXB2) levels. Local ethical approval was granted. Statistical analysis was performed using SPSS17. Results: The overall rate of aspirin resistance varied from 2.4% to 63.5% depending on the assay used. Significant inter- and intra-individual variability existed at baseline and on placebo testing between assays. Assay sensitivities ranged from 24.0% (OPA ADP10) to 87.8% (serum TXB2), and specificities from 81.0% (PFA-100™) to 97.4% (serum TXB2). Selection of alternative "cut-off" values resulted in differing prevalence rates of biochemical aspirin resistance with a trade-off between sensitivity and specificity. Conclusions: Response to aspirin shows marked inter-assay, inter-individual and temporal variability. Testing on multiple occasions using several assays is necessary to reliably diagnose aspirin resistance. Selection of alternative assay "cut-off" values should be considered when formally assessing aspirin response

Assistantship improves medical students' perception of their preparedness for starting work.

BACKGROUND: The GMC has recommended introducing student assistantships during which final year students, under supervision, undertake most of the responsibilities of a FY1 doctor. The Medical School at Queen's University Belfast in 2011/12 introduced an assistantship programme. We have evaluated the impact of the assistantship on students' perception of their preparedness for starting work. METHODS: Students were asked to complete a questionnaire at the beginning of the assistantship. It assessed the students' perception of their preparedness in five areas: clinical and practical skills, communications skills, teaching and learning, understanding the work environment and team working. After the assistantship they again completed the questionnaire. Comparison of the results allowed an assessment of the impact of the assistantship. RESULTS: There was a statistically significant improvement in the students' perception of their preparation for 49 of 56 tasks contained within the questionnaire. After the assistantship 81.2% of students felt well prepared for starting work compared with 38.9% before the assistantship. 93.9% agreed that the assistantship had improved their preparedness for starting work. CONCLUSIONS: The assistantship at Queen's University improves medical students' perception of their preparedness for starting work. The majority of medical students feel well prepared for starting work after completing the assistantship.

Association of Clostridium difficile ribotype 078 with detectable toxin in human stool specimens.

Using a Clostridium difficile glutamate dehydrogenase (GDH) immunoassay and a sensitive C. difficile toxin A/B immunoassay, human stool specimens from patients with diarrhoea (n = 1085) were classified as either GDH positive/toxin negative, or GDH positive/toxin positive. Overall, 528/725 (73%) of the GDH-positive/toxin-negative specimens contained viable C. difficile, and 433/528 (82%) of these C. difficile isolates were PCR positive for the toxin gene pathogenicity locus. Overall, 867/1078 (80%) of the GDH-positive specimens contained viable C. difficile, and 433/725 (60%) of the GDH-positive/toxin-negative specimens contained a toxigenic C. difficile strain. The diversity of toxigenic C. difficile ribotypes isolated from toxin-negative specimens (n = 433) and toxin-positive specimens (n = 339) was significantly different (P < 0.0001). Specifically, the presence of ribotype 078 strains was very strongly associated (P < 0.0001) with detection of toxin in clinical specimens using a sensitive toxin immunoassay. Specimens positive for ribotype 078 were almost twice as likely to be toxin positive as opposed to toxin negative (risk ratio = 1.90, 95% confidence interval 1.64-2.19). In contrast, other circulating ribotypes were seen with similar frequency in specimens with and without detectable toxin. This supports the view that ribotype 078 strains may be more virulent than other common ribotypes in terms of toxin production.

The effect of peri-operative blood loss on postoperative pain following total knee arthroplasty.

AIM: This study aimed to investigate a possible link between peri-operative blood loss and post-operative pain following primary total knee arthroplasty (TKA). METHOD: A retrospective study was carried out using data from two RCTs (403 patients). Blood loss was estimated using Gross et al's formula. Blood transfusions were factored into calculations. Pain scores were obtained using a visual analogue score. RESULTS: Multiple regression analysis showed no relationship (0.09) and analysis of variance showed no significant difference (p = 0.597). Null hypothesis accepted. CONCLUSION: Minimising blood-loss remains an important goal during surgery. On-going efforts should be made to improve patient satisfaction following TKA.

Are APLS formulae for estimating weight appropriate for use in children admitted to PICU?

AIM: To determine if the revised APLS UK formulae for estimating weight are appropriate for use in the paediatric intensive care population in the United Kingdom. METHODS: A retrospective observational study involving 10,081 children (5622 male, 4459 female) between the age of term corrected and 15 years, who were admitted to Paediatric Intensive Care Units in the United Kingdom over a five year period between 2006 and 2010. Mean weight was calculated using retrospective data supplied by the 'Paediatric Intensive Care Audit Network' and this was compared to the estimated weight generated using age appropriate APLS UK formulae. RESULTS: The formula 'Weight=(0.5×age in months)+4' significantly overestimates the mean weight of children under 1 year admitted to PICU by between 10% and 25.4%. While the formula 'Weight=(2×age in years)+8' provides an accurate estimate for 1-year-olds, it significantly underestimates the mean weight of 2-5 year olds by between 2.8% and 4.9%. The formula 'Weight=(3×age in years)+7' significantly overestimates the mean weight of 6-11 year olds by between 8.6% and 20.7%. Simple linear regression was used to produce novel formulae for the prediction of the mean weight specifically for the PICU population. CONCLUSIONS: The APLS UK formulae are not appropriate for estimating the weight of children admitted to PICU in the United Kingdom. Relying on mean weight alone will result in significant error as the standard deviation for all age groups are wide.

PET-CT as a predictor of outcome in resectable colorectal liver metastases.

INTRODUCTION: PET-computed tomography (PET-CT) is a useful staging imaging modality in colorectal liver metastases (CRLM). This study aimed to determine whether PET-CT parameters, standardized uptake value (SUV) and reconstructed tumour volume (RTV), are predictors of prognosis and survival. METHODS: A study of all resectable CRLM patients in the regional HPB unit from 2007-2009 was performed. Preoperative PET-CT scans were retrospectively reviewed; SUV, diameter and RTV for each lesion was recorded. Correlation analysis was performed with other pathological and biochemical parameters, by Pearson's correlation analysis. Survival analysis was performed using Cox regression hazard model. A P value of less than 0.05 was considered statistically significant. RESULTS: A total of 79 patients were included. SUV moderately correlated with tumour diameter, both PET-CT (r=0.4927; P<0.0001) and histology (r=0.4513; P=0.0003); RTV (r=0.4489; P<0.001), preoperative carcinoembryonic antigen (CEA) (r=0.4977; P=0.0001), and postoperative CEA (r=0.3727; P=0.004). Multivariate analysis found that an independent predictor of SUVmax was preoperative CEA (P=0.03). RTV strongly correlated with preoperative CEA (r=0.9389; P<0.0001). SUV and RTV had a negative effect on survival. CONCLUSION: PET-CT, in the setting of CRLM, may have a prognostic role in assessing survival. Although no definite conclusions can be drawn regarding the prognostic role of SUV and RTV, it acts to reinforce the need for further prospective studies to validate these findings.

Functional outcomes following syndesmotic fixation: A comparison of screws retained in situ versus routine removal - Is it really necessary?

INTRODUCTION: Syndesmotic disruption can occur in up to 20% of ankle fractures and is more common in Weber Type C injuries. Syndesmotic repair aims to restore ankle stability. Routine removal of syndesmosis screws is advocated to avoid implant breakage and adverse functional outcome such as pain and stiffness, but conflicting evidence exists to support this. The aim of the current study is to determine whether functional outcome differs in patients who had syndesmosis screws routinely removed, compared to those who did not, and whether a cost benefit exists if removal of screws is not routinely necessary. PATIENTS AND METHODS: A retrospective review of consecutive syndesmosis repairs was performed from 1 January 2008 to 31 December 2010 in a single regional trauma centre. We identified 91 patients who had undergone open reduction internal fixation of an ankle fracture with placement of a syndesmosis screw at index procedure. As many as 69 patients were eligible for the study as defined by the inclusion criteria and they completed a validated functional outcome questionnaire. The functional outcomes of patients with 'retained screws' and 'removed screws' were analysed and compared using the Olerud Molander Ankle Score (OMAS). RESULTS: A total of 63 patients responded with a mean follow-up period of 31 months (range 10-43 months). Of those patients, 43 underwent routine screw removal whilst 20 had screws left in situ. The groups were comparable considering age, gender and follow-up time. The 'retained' group scored higher mean OMAS scores, 81.5±19.3 compared to 75±12.9 in the 'removed' group (p=0.107). The retained group achieved higher functional scores in each of the OMAS domains as well as experiencing less pain. When adjusted for gender, the findings were found to be statistically significant (p=0.046). CONCLUSION: Our study has shown that retained-screw fixation does not significantly impair functional capacity, with additional cost-effectiveness. We therefore advocate that syndesmosis screws be left in situ and should only be removed in case of symptomatic implants beyond 6 months postoperatively.

Lithium usage and renal function testing in a large UK community population; a case-control study.

OBJECTIVE: This study investigates the prevalence of lithium use, monitoring practice and associated effects on renal function in a large UK community sample. METHOD: A large population-based renal function database was cross-referenced with a general practitioner database of 404,673 patients. The renal function of patients prescribed lithium during the 2-year period was compared with that of matched controls. The renal monitoring patterns of these cases were investigated in a naturalistic observational study. Data underwent parametric testing - continuous variables by analysis of variance, with appropriate adjustment, and categorical outcomes by χ(2) testing. Block analysis of variance was undertaken on case-control data. RESULTS: A total of 422 patients in the database were prescribed lithium. Renal function monitoring in accordance with published guidelines occurred in 69% of patients. Patients taking lithium had a significantly higher serum creatinine (5.8 µmol/L, P<.001) and lower glomerular filtration rate (5.9 ml/min, P<.001) when compared to matched controls. CONCLUSIONS: This is the first study carried out in a large community sample. Lithium remains widely prescribed in the community setting. The study confirms that lithium has a statistically and clinically significant negative effect on renal function. Despite published guidelines and recognition of the importance of serial measurements, monitoring of renal function is inconsistent.

Is dieting behaviour decreasing in young adolescents?

OBJECTIVE: To report trends in underweight, overweight and obesity in 12-15-year-old adolescents and examine changes in dieting behaviour, which have been less well documented. DESIGN: Comparison of two independent representative cross-sectional surveys. SETTING: Northern Ireland. SUBJECTS: Weight and height were objectively measured in 1324 boys and 1160 girls in 1996 and 1274 boys and 1374 girls in 2007. Participants reported whether they were following any particular diet including a self-proposed or prescribed weight-reduction diet. RESULTS: Overweight and obesity increased in girls from 15 % to 23 % and 2 % to 6 %, respectively. Increases were more modest in boys with overweight increasing from 13 % to 18 % and obesity from 3 % to 6 %. The proportion of underweight adolescents decreased from 9 % to 6 % in girls and 8 % to 5 % in boys. Evidence of social disparity was observed in girls from a manual socio-economic background, with overweight/obesity prevalence rates increasing from 21 % to 36 % compared with 15 % to 26 % in girls from a non-manual background. Despite these trends fewer adolescents, in particular girls, reported following weight-reduction diets (14 % of overweight/obese girls in 2007 v. 21 % in 1996; 8 % of boys in 2007 v. 13 % in 1996). Of these girls, the proportion from a manual background following weight-reduction diets decreased from 25 % to 11 %. CONCLUSIONS: Overweight and obesity are continuing to increase in adolescents despite government and media awareness strategies. There also appears to be reduced dieting behaviour, despite increasing body weight, particularly in girls from manual socio-economic backgrounds.

Optimization of the precordial leads of the 12-lead electrocardiogram may improve detection of ST-segment elevation myocardial infarction.

BACKGROUND: For the assessment of patients with chest pain, the 12-lead electrocardiogram (ECG) is the initial investigation. Major management decisions are based on the ECG findings, both for attempted coronary artery revascularization and risk stratification. The aim of this study was to determine if the current 6 precordial leads (V(1)-V(6)) are optimally located for the detection of ST-segment elevation in ST-segment elevation myocardial infarction (STEMI). METHODS: We analyzed 528 (38% anterior [200], 44% inferior [233], and 18% lateral [95]) patients with STEMI with both a 12-lead ECG and an 80-lead body surface map (BSM) ECG (Prime ECG, Heartscape Technologies, Bangor, Northern Ireland). Body surface map was recorded within 15 minutes of the 12-lead ECG during the acute event and before revascularization. ST-segment elevation of each lead on the BSM was compared with the corresponding 12-lead precordial leads (V(1)-V(6)) for anterior STEMI. In addition, for lateral STEMI, leads I and aVL of the BSM were also compared; and limb leads II, III, aVF of the BSM were compared with inferior unipolar BSM leads for inferior STEMI. Leads with the greatest mean ST-segment elevation were selected, and significance was determined by analysis of variance of the mean ST segment. RESULTS: For anterior STEMI, leads V(1), V(2), 32, 42, 51, and 57 had the greatest mean ST elevation. These leads are located in the same horizontal plane as that of V(1) and V(2). Lead 32 had a significantly greater mean ST elevation than the corresponding precordial lead V(3) (P = .012); and leads 42, 51, and 57 were also significantly greater than corresponding leads V(4), V(5), V(6), respectively (P < .001). Similar findings were also found for lateral STEMI. For inferior STEMI, the limb leads of the BSM (II, III, and aVF) had the greatest mean ST-segment elevation; and lead III was significantly superior to the inferior unipolar leads (7, 17, 27, 37, 47, 55, and 61) of the BSM (P < .001). CONCLUSION: Leads placed on a horizontal strip, in line with leads V(1) and V(2), provided the optimal placement for the diagnosis of anterior and lateral STEMI and appear superior to leads V(3), V(4), V(5), and V(6). This is of significant clinical interest, not only for ease and replication of lead placement but also may lead to increased recruitment of patients eligible for revascularization with none or borderline ST-segment elevation on the initial 12-lead ECG.

Neurodevelopment of children exposed in utero to lamotrigine, sodium valproate and carbamazepine.

OBJECTIVE: To establish the relative risks of in utero exposure to lamotrigine (LTG), sodium valproate (NaV) and carbamazepine (CBZ) monotherapy for neurodevelopment. DESIGN: Observational cohort study. PATIENTS AND METHODS: The study group consisted of children in Northern Ireland aged 9-60 months born to mothers who had enrolled with the UK Epilepsy and Pregnancy Register. The control group consisted of children identified from the Child Health System database across Northern Ireland. Data were gathered on covariates recognised as influencing child development. MAIN OUTCOME MEASURES: Neurodevelopment assessed using either the Bayley Scales of Infant Development or the Griffiths Mental Development Scales. RESULTS: 210 children underwent assessment by a single researcher blinded to antiepileptic drug exposure. 23 (39.6%) children exposed in utero to NaV, 10 (20.4%) exposed to CBZ and one (2.9%) exposed to LTG had evidence of mild or significant developmental delay, compared to two (4.5%) children in the control group. Multivariable analysis demonstrated that in utero exposure to NaV (OR 26.1, 95% CI 4.9 to 139; p<0.001) and to CBZ (OR 7.7, 95% CI 1.4 to 43.1; p<0.01) but not to LTG had a significant detrimental effect on neurodevelopment. CONCLUSION: In utero exposure to LTG did not have the detrimental effect on child development that was seen with NaV and with CBZ.

Long-term occlusal and soft-tissue profile outcomes after treatment of Class II Division 1 malocclusion with fixed appliances.

INTRODUCTION: Our objective was to determine which factors were predictive of good long-term outcomes after fixed appliance treatment of Class II Division 1 malocclusion. METHODS: Two hundred seven patients with Class II Division 1 malocclusion were examined in early adulthood at a mean of 4.6 years after treatment with fixed appliances. The peer assessment rating index was used to evaluate dental alignment and occlusal relationships. The soft-tissue profile was assessed with the Holdaway angle. RESULTS: Logistic regression identified 3 pretreatment variables that were predictive of a good facial profile (Holdaway angle) at recall: the lower lip to E-plane distance (P <0.001; smaller distance behind the E-plane means a better outcome), ANB angle (P = 0.001; smaller ANB means a better outcome), and extraction pattern (P = 0.026). Linear regression analysis showed that 2 pretreatment variables were predictive of a favorable PAR score at recall: SNB angle (P = 0.001; larger SNB means a better outcome) and extraction pattern (P = 0.034). CONCLUSIONS: Three pretreatment cephalometric measures (lower lip to E-plane distance, ANB angle, and SNB angle) were predictive of the outcome in the treatment of Class II Division 1 malocclusion. The extraction pattern was also found to be a predictor of outcome.

Age-related changes in energy efficiency of gait, activity, and participation in children with cerebral palsy.

AIM: The aim of this study was to use a prospective longitudinal study to describe age-related trends in energy efficiency during gait, activity, and participation in ambulatory children with cerebral palsy (CP). METHOD: Gross Motor Function Measure (GMFM), Paediatric Evaluation of Disability Inventory (PEDI), and Lifestyle Assessment Questionnaire-Cerebral Palsy (LAQ-CP) scores, and energy efficiency (oxygen cost) during gait were assessed in representative sample of 184 children (112 male; 72 female; mean age 10y 9mo; range 4-16y) with CP. Ninety-four children had unilateral spastic CP, 84 bilateral spastic CP, and six had other forms of CP. Fifty-seven were classified as Gross Motor Function Classification System (GMFCS) level I, 91 as level II, 22 as level III, and 14 as level IV). Assessments were carried out on two occasions (visit 1 and visit 2) separated by an interval of 2 years and 7 months. A total of 157 participants returned for reassessment. RESULTS: Significant improvements in mean raw scores for GMFM, PEDI, and LAQ-CP were recorded; however, mean raw oxygen cost deteriorated over time. Age-related trends revealed gait to be most inefficient at the age of 12 years, but GMFM scores continued to improve until the age of 13 years, and two PEDI subscales to age 14 years, before deteriorating (p<0.05). Baseline score was consistently the single greatest predictor of visit 2 score. Substantial agreement in GMFCS ratings over time was achieved (κ(lw) =0.74-0.76). INTERPRETATION: These findings have implications in terms of optimal provision and delivery of services for young people with CP to maximize physical capabilities and maintain functional skills into adulthood.

Preparing students for interprofessional practice: exploring the intra-personal dimension.

The need for interprofessional education is now firmly embedded in undergraduate healthcare curricula frameworks in Northern Ireland and has a role to play in preparation for professional practice. A questionnaire determining students' "readiness" for interprofessional education has been widely used and reported in the literature but there are other factors that contribute to students' abilities to learn in an interprofessional context. Pre-qualification healthcare education can be viewed as having three inter-related components, intra-professional, interprofessional and intra-personal learning; the third of these underpinning the other two. Understanding more about personal learning needs can contribute to preparation for interprofessional interaction. A Studying and Learning Preferences Inventory (SALPI) was developed and validated for use with a range of healthcare professionals to assist in this process.

Self-perception of dentofacial attractiveness among patients requiring orthognathic surgery.

OBJECTIVE: To test the hypothesis that the self-perception of dental and facial attractiveness among patients requiring orthognathic surgery is no different from that of control patients. MATERIALS AND METHODS: Happiness with dental and facial appearance was assessed using questionnaires completed by 162 patients who required orthognathic treatment and 157 control subjects. Visual analog scale, binary, and open response data were collected. Analysis was carried out using a general linear model, logistic regression, and chi-square tests. RESULTS: Orthognathic patients were less happy with their dental appearance than were controls. Class II patients and women had lower happiness scores for their dental appearance. Among orthognathic patients, the "shape" and "prominence" of their teeth were the most frequent causes of concern. Older subjects, women, and orthognathic patients were less happy with their facial appearance. Class III orthognathic patients, older subjects, and women were more likely to have looked at their own face in profile. A greater proportion of Class II subjects than Class III subjects wished to change their appearance. CONCLUSIONS: The hypothesis is rejected. The findings indicate that women and patients requiring orthognathic surgery had lower levels of happiness with their dentofacial appearance. Although Class II patients exhibited the lowest levels of happiness with their dental appearance, there was some evidence that concerns and awareness about their facial profile were more pronounced among the Class III patients.

Planning a cluster randomized controlled trial: methodological issues.

BACKGROUND: The standard approach in a randomized controlled trial (RCT) is to randomize individuals to intervention and control groups. Yet, nursing and other health interventions are often implemented at the levels of health service organizational unit or geographical area. It may be more appropriate to conduct a cluster RCT. However, cluster randomization requires consideration of a number of important issues. OBJECTIVE: The objective of this study was to show how critical issues in relation to design and analysis can be addressed. APPROACH: Two cluster RCTs conducted by the authors are used as examples. Guidance on the conduct and reporting of cluster RCTs is also offered. RESULTS: A rationale for choosing this design was provided, and issues in relation to study design, calculation of sample size, and statistical analysis were clarified. A decision tree and checklist are provided to guide researchers through essential steps in conducting a cluster RCT. DISCUSSION: Cluster RCTs present special challenges in relation to design, conduct, and analysis. Nevertheless, they are an appropriate and potentially powerful tool for nursing research. With careful attention to the issues addressed in this article, researchers can use this approach successfully.

Test-retest reliability of a 1-min walk test in children with bilateral spastic cerebral palsy (BSCP).

The test-retest reliability of a 1-min walk test at a child's maximum walking speed was assessed in children with bilateral spastic cerebral palsy (BSCP). Twelve male and five female children (age range 3-18 years, mean age 12 years 8 months) participated in the study. Children were classified as GMFCS level I (n=5), level II (n=8) and level III (n=4). Results showed that for walk tests performed on different days, distances varied by no more than 13.1m (for 95% of participants) and that a practice walk was vital for reducing systematic bias. The intraclass correlation coefficient was 0.94. A 1-min walk test is a reliable method of assessing function in children with CP but care must be taken when interpreting changes in individual patient data.

A pilot study of a low-tilt biphasic waveform for transvenous cardioversion of atrial fibrillation: improved efficacy compared with conventional capacitor-based waveforms in patients.

BACKGROUND: The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. METHODS: We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for >/=30 seconds. RESULTS: The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). CONCLUSION: The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage).