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PubMed2005

Epidemiological evidence on multiple system atrophy.

Multiple system atrophy (MSA), is a sporadic neurodegenerative disorder characterized clinically by any combination of parkinsonian, autonomic, cerebellar or pyramidal symptoms and signs. The frequence of disease is estimated for the incidence rate to 0.6 cases per 100.000 person-years, while the prevalence rate is included between 1.86 and 4.9 cases per 100.000 pop. A risk factor seems to be the occupational history of farming also if the occupational exposure to pesticides is not associated with MSA. Smoking is probably a protective factor in MSA as Parkinson's disease. MSA seems a sporadic disease also if recently a German family with two MSA cases has been reported. The polymorphism association studies support a role for inflammation-related genes in risk for MSA. The current epidemiological and clinical evidence suggests that likely the etiopathogenesis of MSA is complex, and that many genetic as well as environmental factors are involved. Unfortunately, the most of studies in MSA are lacking in a sample size estimate to test the hypothesis, then the scientific evidence is poor. Then, much larger numbers of cases and controls are necessary for these studies to reach sufficient power, but collecting such large numbers is feasible only in the framework of multicentric consortia.

Animals↗
PubMed1992

The Modification of Diet in Renal Disease Study: design, methods, and results from the feasibility study.

The Modification of Diet in Renal Disease (MDRD) Study is a multicenter clinical trial designed to assess acceptance, safety, and efficacy of restricted protein and phosphorus diets in patients with progressive renal disease. The Feasibility Study was designed to test procedures and recruitment strategies and to estimate sample size for the Full-Scale Trial. The Feasibility Study was not designed to compare rates of progression of renal disease among diet groups. Patients aged 18 to 75 years, with a glomerular filtration rate (GFR; measured by 125I-iothalamate clearance) between 7.5 and 80 mL/min/1.73 m2, and a previous progressive increase in serum creatinine, were eligible for enrollment. Compliance with prescribed dietary protein intake was calculated from urea nitrogen appearance (UNA). Nutritional status was monitored by anthropometry and serum proteins. Progression of renal disease was calculated as the rate of decline of GFR. Ninety-six patients met all of the eligibility requirements and were randomized to study diets. Follow-up was conducted for a mean duration of 14 months (range, 2 to 22 months). Although most patients did not achieve the prescribed protein intake, marked changes in intake were observed among patients assigned to the low-protein diets, and mean estimated protein intake differed significantly among diet groups. No patients became malnourished. Mean rates of decline in GFR were relatively slow, and variability among individuals was high. As expected, the number of patients enrolled was too small to determine if the rate of decline in GFR was significantly slower among patients assigned to the restricted protein and phosphorus diets. The rate of decline in GFR was significantly inversely correlated with long-term average mean arterial blood pressure (MAP), even among patients whose blood pressure was controlled to levels within the normal range. However, because patients were not randomly assigned blood pressure goals, it was not possible to determine whether a causal relationship exists. Based on the experience gained during the Feasibility Study, the design for the Full-Scale Study includes two studies of defined by patients' baseline levels of renal function. Within each study, patients will be assigned randomly to one of two diets, and within each diet group, to one of two levels of blood pressure control. Based on variability of rates of decline in GFR slopes observed during the Feasibility Study, 800 patients with follow-up periods of up to 4 years will be required for the Full-Scale Trial.

Adult↗
PubMed1991

Data analysis and sample size issues in evaluations of community-based health promotion and disease prevention programs: a mixed-model analysis of variance approach.

The growing interest in community-based approaches to health promotion and disease prevention (HP/DP) has been accompanied by a growing need to evaluate the effectiveness of such programs. Special issues that arise in these evaluation studies include (1) entire communities are assigned to intervention and control groups, (2) only a small number of communities can usually be studied, (3) the time course of changes in behavior and other outcomes is often of interest, and (4) surveys to measure such changes over time can be conducted with either repeated cross-sectional samples or with longitudinal samples. This paper shows how these issues can be addressed under a mixed-model analysis of variance approach. This approach serves to unify several ideas in the literature on evaluation of community studies, including use of time-series regression and the question of whether the individual or the community should be the unit of analysis. We also describe how the method can be used to estimate sample size requirements, statistical power, or minimum detectable program effect.

Analysis of Variance↗
PubMed1999

ASSENCE (assessment of cost-effectiveness of several strategies of early diagnosis in patients with acute chest pain and non-conclusive electrocardiogram).

Clinical, economical, organizative, and medico-legal issues raised by management of citizens who come to Emergency Department with acute chest pain and non diagnostic electrocardiogram are well known. Data from the Italian Health Ministry show that, in 1996, 37,444 patients had been discharged from Italian hospitals with the main diagnosis of chest pain. To obtain this "non-diagnosis", it was needed a mean hospital stay of 4.2 days with estimated costs close to $57,000,000. The ASSENCE study is a randomized, multicenter, international trial aimed at comparing three strategies of handling citizens presenting to emergency department for unexplained chest pain in terms of cost/effectiveness ratio and quality of patients' life. The three strategies that will be compared are: 1. current clinical protocols, prescribing an in-hospital observation period and discharge after several hours/days; 2. performing a dobutamine-atropine stress echocardiography between 0 and 18 hours after randomization (at 6 hours after index chest pain onset) and discharging the patients (if negative) immediately thereafter; 3. performing an electrocardiographic exercise stress test between 0 and 18 hours after randomization and discharging the patients (if negative) immediately thereafter. The main ASSENCE study end-point will be assessment of cost/effectiveness of the 3 strategies tested. Costs will be assessed taking into account: hospital stay length, performed diagnostic procedures and treatments during index admission, in-hospital and 2-month follow-up events (cardiac death, myocardial infarction, definite unstable angina, coronary angioplasty, by-pass surgery, re-admission to hospital for chest-pain). A secondary ASSENCE study end-point will be to assess the effect on patient quality of life of the use of the 3 strategies tested. Sample size estimation calculated in order to detect an absolute difference of at least 10% and based on a 30% expected rate of events, was of 186 patients for each strategy tested.

Acute Disease↗
PubMed2002

The Thai logarithmic visual acuity chart.

OBJECTIVE: To evaluate visual acuity scores from the Thai and the standard logarithmic visual acuity chart. DESIGN: Comparative non-randomized clinical study. PARTICIPANTS AND METHOD: 153 subjects, calculated from sample size estimation, without any ocular disease and aged between 18 and 80 years old who could read English and at least 3 out of 5 letters of the largest line of both charts were enrolled to use only their right eyes to read the Thai and the standard logarithmic visual acuity chart without any refractive correction. 27 subjects came back for second measurements of visual acuity in the same manner as the first a week later. MAIN OUTCOME MEASUREMENT: The visual acuity scores were divided into the Snellen or the whole line score and the ETDRS or the letter-by-letter score. The former was compared by weighted Kappa and the latter was compared by the paired t-test. RESULTS: There was high agreement in weighted Kappa between the Snellen scores from the Thai and standard chart (k = 0.7375). There was also high agreement in weighted Kappa between the Snellen scores from the first and second reading of the Thai chart (k = 0.7304) and the standard chart (k = 0.7282). A high correlation was observed between the ETDRS scores from the Thai and standard charts (r = 0.947). Also there was a high correlation between the ETDRS scores of the first and second reading of both the Thai chart (r = 0.962) and the standard chart (r = 0.952). There was a significant difference between the ETDRS scores from the Thai and standard chart (p<0.0001). There was no significant difference between the ETDRS scores from the first and second reading of either the Thai chart (p = 0.794) or the standard chart (p = 0.62). CONCLUSION: The Snellen visual acuity score from the Thai chart is comparable to the standard chart. Although the ETDRS score from the Thai chart is different statistically from the standard chart, its test-retest variability tends to be low. This suggests the possibility of using the Thai chart for monitoring of the ETDRS score in research studies.

Adolescent↗
PubMed1996

The feasibility of a randomized clinical perinatal trial: maternal magnesium sulfate for the prevention of cerebral palsy.

OBJECTIVE: Because recent epidemiologic data suggest an association between maternal magnesium sulfate use and a decreased risk of cerebral palsy in infants who survive preterm birth, we investigated the feasibility of a randomized trial of intrapartum maternally administered magnesium sulfate to prevent cerebral palsy in children who were born before term. STUDY DESIGN: On the basis of a literature review, we calculated cumulative rates of delivery, neonatal survival, and cerebral palsy for progressively longer gestational age intervals beginning at 24 weeks' gestation. Sample size estimates with two-tailed chi 2 tests without Yates' correction (alpha = 0.05, beta = 0.2, 50% effect size) for a clinical trial were calculated for these rates. RESULTS: In the 4-week interval from 24 weeks 0 days to 27 weeks 6 days the minimum number of neonates required to conduct a randomized trial would be 1189. Loss to follow-up of neonates, maternal ineligibility, and failure of enrollment would substantially increase the number of necessary gravid women delivered in the 4-week interval to complete such a trial, such that 1 million pregnancies would be required to generate the necessary number of eligible gravid women. Shorter gestational age intervals (e.g., 24 weeks 0 days to 25 weeks 6 days) required fewer neonates (n = 729) but more pregnancies (n = 1.5 million). Because of the decreasing prevalence of cerebral palsy at higher gestational ages, extending the gestational age interval (e.g., to 29 weeks 6 days) markedly increased the minimum number of neonates to 1982 but only slightly decreased the necessary number of pregnancies, to 900,000. CONCLUSIONS: A randomized trial of maternally administered intrapartum magnesium sulfate to reduce the rate of cerebral palsy in surviving preterm neonates would be a formidable undertaking, requiring a concerted multicentered effort.

Cerebral Palsy↗
PubMed2004

The American College of Rheumatology response criteria for systemic lupus erythematosus clinical trials: measures of overall disease activity.

OBJECTIVE: Improved standards for the evaluation of therapeutic interventions in systemic lupus erythematosus (SLE) are needed. The purpose of this study by a committee of the American College of Rheumatology was to define clinically meaningful improvement, no change, or worsening in 6 existing clinical measures of SLE disease activity. This represents an important step in a disease in which some organ symptoms get better and others get worse. It is intended to help investigators develop sample size estimates based on meaningful effect sizes and to gauge the clinical relevance of any observed change in disease activity. METHODS: Medical records from 310 patients drawn from 3 sources were abstracted into a standard format. Each vignette included clinical and laboratory data obtained during 2-3 visits. Ratings on the following 6 instruments were obtained for the same patients during the visit or retrospectively: the British Isles Lupus Assessment Group (BILAG), the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), the revised Systemic Lupus Activity Measure (SLAM-R), the European Consensus Lupus Activity Measure (ECLAM), the Safety of Estrogens in Lupus Erythematosus: National Assessment (SELENA)-SLEDAI, and the Responder Index for Lupus Erythematosus (RIFLE). From this pool of vignettes, 5 common vignettes and 10 randomly selected vignettes were rated through a secure Web site by 88 international experts on SLE. The experts, who were blinded to the activity measure scores, were asked to rate each patient's clinical condition as worsened, improved, or unchanged relative to the previous visit. These ratings were transformed by statistical procedures into performance characteristic curves that related a change on a particular SLE activity measure to the physicians' agreement on whether that patient had worsened, improved, or remained the same clinically. These were discussed by the committee members, who were blinded to the actual instrument used. The committee then voted on what level of expert agreement would be used to determine clinically meaningful change. RESULTS: The physician ratings on the 5 common vignettes revealed considerable variation in their clinical appraisals. Overall, the 6 SLE activity measures showed excellent separation of clinical conditions as being worsened, improved, or the same. The committee voted to take 70% agreement by physicians as the point on the performance characteristic curves at which meaningful change in a score could be identified. For each instrument, we computed the units of change required to indicate improvement or worsening. CONCLUSION: To our knowledge, these are the first response criteria in any disease where a clinically relevant change has been determined a priori and mapped to standardized measures. This criterion should aid the clinical evaluation of new therapies, improve comparability between trials, and facilitate innovative trial designs.

Clinical Trials as Topic↗
PubMed2005

Randomized trials stopped early for benefit: a systematic review.

CONTEXT: Randomized clinical trials (RCTs) that stop earlier than planned because of apparent benefit often receive great attention and affect clinical practice. Their prevalence, the magnitude and plausibility of their treatment effects, and the extent to which they report information about how investigators decided to stop early are, however, unknown. OBJECTIVE: To evaluate the epidemiology and reporting quality of RCTs involving interventions stopped early for benefit. DATA SOURCES: Systematic review up to November 2004 of MEDLINE, EMBASE, Current Contents, and full-text journal content databases to identify RCTs stopped early for benefit. STUDY SELECTION: Randomized clinical trials of any intervention reported as having stopped early because of results favoring the intervention. There were no exclusion criteria. DATA EXTRACTION: Twelve reviewers working independently and in duplicate abstracted data on content area and type of intervention tested, reporting of funding, type of end point driving study termination, treatment effect, length of follow-up, estimated sample size and total sample studied, role of a data and safety monitoring board in stopping the study, number of interim analyses planned and conducted, and existence and type of monitoring methods, statistical boundaries, and adjustment procedures for interim analyses and early stopping. DATA SYNTHESIS: Of 143 RCTs stopped early for benefit, the majority (92) were published in 5 high-impact medical journals. Typically, these were industry-funded drug trials in cardiology, cancer, and human immunodeficiency virus/AIDS. The proportion of all RCTs published in high-impact journals that were stopped early for benefit increased from 0.5% in 1990-1994 to 1.2% in 2000-2004 (P<.001 for trend). On average, RCTs recruited 63% (SD, 25%) of the planned sample and stopped after a median of 13 (interquartile range [IQR], 3-25) months of follow-up, 1 interim analysis, and when a median of 66 (IQR, 23-195) patients had experienced the end point driving study termination (event). The median risk ratio among truncated RCTs was 0.53 (IQR, 0.28-0.66). One hundred thirty-five (94%) of the 143 RCTs did not report at least 1 of the following: the planned sample size (n = 28), the interim analysis after which the trial was stopped (n = 45), whether a stopping rule informed the decision (n = 48), or an adjusted analysis accounting for interim monitoring and truncation (n = 129). Trials with fewer events yielded greater treatment effects (odds ratio, 28; 95% confidence interval, 11-73). CONCLUSIONS: RCTs stopped early for benefit are becoming more common, often fail to adequately report relevant information about the decision to stop early, and show implausibly large treatment effects, particularly when the number of events is small. These findings suggest clinicians should view the results of such trials with skepticism.

Clinical Trials Data Monitoring Committees↗
PubMed2000

Non-aspirin, non-steroidal anti-inflammatory drugs for osteoarthritis of the knee.

OBJECTIVES: To determine whether there is a difference in the relative efficacy of individual non-steroidal anti-inflammatory drugs (NSAIDs) when used in the management of osteoarthritis (OA) of the knee. SEARCH STRATEGY: We searched Medline (1966-1995) and Bids Embase (Jan-Dec, 1980-1995). The searches were limited to publications in the English language, and were last perfomed in November 1996. We used modified Cochrane Collaboration search strategy to identify all randomised controlled trials. The MeSH heading osteoarthritis was combined with the generic names of the 17 non-aspirin NSAIDs licensed in the UK for the management of OA in general practice. The search of Embase used the term "osteoarthritis" if present in the abstract, title or keywords, and was combined with the generic names of the 17 non-aspirin NSAIDs, only if they were mentioned in the title, abstract or keywords. SELECTION CRITERIA: All double blind, randomised controlled trials, in the English language, comparing the efficacy of two non-aspirin NSAIDs in the management of osteoarthritis of the knee, were selected. Only trials with subjects aged 16 years and over, with clinical and/or radiological confirmation of the diagnosis of OA knee were included. Studies which compared one "trial" NSAID with one "reference" NSAID were included provided they were non-aspirin NSAIDs available in the UK and were licensed for the treatment of OA by general practitioners. Trials which were placebo-controlled and which also involved the comparison of two NSAIDs were also included. DATA COLLECTION AND ANALYSIS: The methodological design of each study was scored according to a pre-determined system. The three main outcome measures of pain, physical function and patient global assessment were chosen based on the core set agreed upon by OMERACT (Outcome Measures in Rheumatology Clinical Trials). These were used to determine the power of each trial. The equivalency of NSAID doses was calculated using the percentage of the recommended maximum daily dose. Sample size estimates for the detection of clinically relevant changes in outcome measures used in the assessment of OA knee were used for power calculations. These calculations were performed to determine whether the trials were of a sufficient size to detect clinically relevant differences which were statistically significant. The calculations incorporate estimates of standard deviation, and minimum, median and maximum differences (delta) between drugs which are deemed to be clinically important. The number of "withdrawals due to lack of efficacy" was also selected as an outcome measure for this review. The Peto odds ratio and 95% confidence intervals were calculated where possible. The results of studies which compared the same trial and reference NSAIDs were combined where possible. MAIN RESULTS: Of the 1151 trials identified by the search strategy, 22 involved knee osteoarthritis only. Sixteen of these trials fulfilled the inclusion criteria and were entered in the review. Eight NSAIDs were represented in these trials. Etodolac was represented in 11 trials. The reference NSAID in these trials was piroxicam (n=3), naproxen(n=3), diclofenac (n=3), indomethacin (n=1), and, nabumetone (n=1). The reported methodological design of the trials was poor, with a median score of 3 (out of a maximum of 8). The results of the trials comparing the same trial and reference NSAIDs were pooled for the outcome "withdrawal due to lack of efficacy". For the comparison, etodolac vesus piroxicam, the odds ratio favoured etodolac i.e. patients receiving etodolac were less likely to withdraw due to lack of efficacy. The dose of etodolac used in each of these three studies, however, was greater than the corresponding dose of piroxicam (based on percentage maximum daily dose). The significance of these results is therefore questionable. For the comparisons etodolac versus diclofenac, and etodolac versus naproxen, there were no clear differences betw

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

Cerebrospinal fluid drainage for thoracic and thoracoabdominal aortic aneurysm surgery.

BACKGROUND: During aortic aneurysm surgery, cross-clamping can lead to inadequate blood supply to the spinal cord resulting in neurological deficit. Cerebrospinal fluid drainage (CSFD) may increase the perfusion pressure to the spinal cord and hence reduce the risk of ischaemic spinal cord injury. OBJECTIVES: To determine the effect of CSFD during thoracic and thoracoabdominal aortic aneurysm (TAAA) surgery on the risk of developing spinal cord injury. SEARCH STRATEGY: The reviewers searched the Cochrane Peripheral Vascular Diseases Group Specialised Trials Register (last searched October 2003), the Cochrane Central Register of Controlled Trials (CENTRAL) database (last searched Issue 4, 2003), MEDLINE and EMBASE, and reference lists of relevant articles. Recent conference proceedings were scanned. SELECTION CRITERIA: Randomised trials involving CSFD during thoracic and TAAA surgery. DATA COLLECTION AND ANALYSIS: Both reviewers assessed the quality of trials independently. One reviewer (SNK) extracted data and the other reviewer (GS) verified the data. MAIN RESULTS: Three trials, with a total of 287 participants operated on for type I or II TAAA, were included. In the first trial of 98 patients, neurological deficits in the lower extremities occurred in 14 (30%) CSFD and 17 (33%) controls. The deficit was observed within 24 hours of the operation in 21 (68%), and from 3 to 22 days in 10 (32%). CSFD did not have a significant benefit in preventing ischaemic injury to the spinal cord. The second trial of 33 patients used a combination of CSFD and intrathecal papaverine. It showed a statistically significant reduction in the rate of postoperative neurological deficit (p = 0.039), compared to controls. Analysis was undertaken after only one third of the estimated sample size had entered the trial. In the third trial TAAA repair was performed on 145 patients. CSFD was initiated during the operation and continued for 48 hours after surgery. Paraplegia or paraparesis occurred in 9 of 74 patients (12.2%) in the control group versus 2 of 82 patients (2.7%) with CSFD (p = 0.03). Overall, CSFD resulted in an 80% reduction in the relative risk of postoperative deficits. Meta-analysis showed an odds ratio (OR) of 0.48 (0.25 to 0.92; confidence interval (CI) 95%). For CSFD trials only OR was 0.57 (0.28 to 1.17) and for intention-to-treat in CSFD only studies OR remained unchanged. REVIEWER'S CONCLUSIONS: There are limited data supporting the role of CSFD in thoracic and thoracoabdominal aneurysm surgery for prevention of neurological injury. Further clinical and experimental studies are indicated.

Aortic Aneurysm, Abdominal↗
PubMed2004

Pilot clinical trial of dehydroepiandrosterone (DHEA) versus placebo for Sjögren's syndrome.

OBJECTIVE: To screen for potential efficacy and assess feasibility and safety of dehydroepiandrosterone (DHEA) as a treatment for Sjögren's syndrome (SS). METHODS: A 24-week randomized, double-blinded, pilot trial of oral DHEA (200 mg/day) versus placebo was conducted. The primary comparison was to a hypothesized 20% placebo response rate. If 14 consecutive subjects on DHEA did not respond, a Phase III trial would be considered futile. A placebo group of 14 subjects was planned to verify placebo response rate and estimate sample size required for a definitive trial. Response criteria required 20% improvement in at least 2 of 3 domains. Analysis of covariance was used to adjust for baseline differences and for stratified randomization. Outcome measures included visual analog scale questionnaires for dry eye and dry mouth symptoms, lissamine green ocular dye staining and Schirmer I tests, stimulated salivary flow, IgG, and erythrocyte sedimentation rate (ESR). RESULTS: Randomization resulted in 14 DHEA and 14 placebo group subjects. At baseline, mean +/- SD for DHEA versus placebo groups were Schirmer I tests 4.5 +/- 4.5 versus 5.4 +/- 6.1 mm/5 minutes; Van Bijsterveld score 5.3 +/- 2.1 versus 5.5 +/- 2.2; unstimulated saliva 0.03 +/- 0.05 versus 0.04 +/- 0.10 ml/minute; IgG 1,699 +/- 749 versus 1,712 +/- 621 g/dl; and ESR 40 +/- 31 versus 44 +/- 28 mm/hour. Apart from changes over the trial in dry mouth symptoms, no significant differences were noted between the DHEA and placebo groups for dry eye symptoms, objective measures of ocular dryness, stimulated salivary flow; IgG, or ESR. Four DHEA and one placebo group patient dropped out because of adverse effects. Although 7 subjects met response criteria in the DHEA group, 5 met the criteria in the placebo group, and there was no significant difference between groups. CONCLUSION: DHEA showed no evidence of efficacy in SS. Without evidence for efficacy, patients with SS should avoid using unregulated DHEA supplements, since long-term adverse consequences of exposure to this hormone are unknown.

Adjuvants, Immunologic↗
PubMed2004

Power analyses for longitudinal trials and other clustered designs.

Existing methods for power and sample size estimation for longitudinal and other clustered study designs have limited applications. In this paper, we review and extend existing approaches to improve these limitations. In particular, we focus on power analysis for the two most popular approaches for clustered data analysis, the generalized estimating equations and the linear mixed-effects models. By basing the derivation of the power function on the asymptotic distribution of the model estimates, the proposed approach provides estimates of power that are consistent with the methods of inference for data analysis. The proposed methodology is illustrated with numerous examples that are motivated by real study designs.

Clinical Trials as Topic↗
PubMed1993

The use of simulation in the design of two cardiovascular survival studies.

Simulation has become practical as an everyday tool given the wide availability of high performance workstations. We argue that simulation can play an important role in determining the number of patients required in a survival study, particularly if the assumption of proportional hazards does not hold, or if the study design is complex. The argument is illustrated by two examples. The first considers the design of a post myocardial infarction survival trial in which the hazard ratio is not constant. The second provides sample size estimates for a multicentre heart failure study in which both the treatment effect and the control mortality rate vary across centres.

Computer Simulation↗
PubMed1985

Variables affecting short-term prognosis in completed stroke.

After a review of the prognostic factors affecting the short-term outcome of completed stroke, the implications for the design of stroke treatment trials are discussed. These concern stratification variables, patient selection, sample size estimation, length of follow-up, and measures of outcome. Potential variables for stratification are type of stroke (i.e. infarct or hemorrhage), age of the patient, level of consciousness, and preceding hypertension and heart disease.

Acute Disease↗
PubMed1985

Placebo therapy for postmenopausal osteoporosis.

Eighteen postmenopausal osteoporotic (PMO) women on placebo therapy were followed for 1 year. Serial measurements of calcium balance and kinetics, bone histomorphometry, photon absorptiometry, and radiogrammetry were obtained. Few significant changes in balance and kinetics or bone histology were seen in these women over time. Photon absorptiometry and radiogrammetry of the femoral cortex showed a significant annual bone loss however. When compared with premenopausal and healthy postmenopausal women, the annual bone loss in those with PMO was significantly greater. The ability of balance studies, photon absorptiometry, and radiogrammetry to predict the magnitude of this bone loss was similar. Finally, there was an illustration of the use of the estimated variance provided by this study for estimating sample size for future studies.

Aged↗
PubMed1999

[Postoperative nausea and vomiting following stabismus surgery in children. Inhalation anesthesia with sevoflurane-nitrous oxide in comparison with intravenous anesthesia with propofol-remifentanil].

BACKGROUND: Postoperative nausea and vomiting (PONV) is still one of the major problems in strabismus surgery, especially in children. In recent years many studies have been published, suggesting that choosing propofol as the anaesthetic agent may help to reduce the high incidence of PONV in children undergoing strabismus surgery. Experience with remifentanil in children is still very limited and little is known, whether propofol in combination with this new short acting opioid is also superior regarding PONV in squint surgery compared to sevoflurane/N2O. Additionally, little is known, whether the type of operation or the muscle which is operated on has any influence with respect to PONV. METHODS: Following sample size estimation, ethics committee approval and parents informed consent in a prospective, randomised, observer-blind study 105 ASA I and II children aged 3-8 years scheduled for elective strabismus surgery were assigned into one of the following groups: Group TIVA (propofol/remifentanil, n = 53): anaesthesia was induced by remifentanil 0.5 microgram kg-1 min-1 over 2 min (loading phase), followed by 3 mg kg-1 propofol along with 30% O2 in air. After endotracheal intubation anaesthesia was maintained initially with remifentanil 0.25 microgram kg-1 min-1 and propofol 10 mg kg-1 h-1 by constant infusion. In the course of the operation the infusions of the anaesthetics were adjusted to the decreasing need for anaesthesia. Group VOLATIL (sevoflurane/N2O, n = 52): anaesthesia was induced by inhalation of sevoflurane along with 50% O2 in N2O. After endotracheal intubation anaesthesia was maintained with sevoflurane 1.0-1.5 MAC along with 30% O2 in N2O and in the course of the operation the administration of the inhaled anaesthetics was adjusted correspondingly. Preoperatively collected data included gender, age, weight and history of PONV. Intraoperatively collected data consisted of data belonging to routine monitoring (heart rate, blood pressure, peripheral oxygen saturation and temperature) as well as the duration of the operation and anaesthesia and specific data regarding the operation (including the number and type of muscles as well as the kind of operation). Data collected within the first 24 hours postoperatively in the recovery room and on the ward by blinded observers included any PONV events as well as the antiemetics and analgesics applied. RESULTS: Vomiting was observed less frequently in the TIVA-group than in the VOLATIL-group (21 of 53 vs. 32 of 52, p = 0.03) within the first 24 hours postoperatively. Posterior fixation suture ("faden-operation") compared to other operations was followed rather frequently by nausea and vomiting (30 of 44 and 33 of 44, respectively), whereas recessions were rarely associated with nausea and vomiting (12 of 35 and 9 of 35, respectively). CONCLUSIONS: TIVA with propofol/remifentanil proved to be a suitable form of anaesthesia for children in this setting. Propofol showed advantages over sevoflurane/N2O with respect to PONV after squint surgery in children also when applied in the combination with remifentanil. TIVA with propofol/remifentanil may therefore be one way to reduce the high incidence of PONV in this setting, bearing in mind, that PONV is not only influenced by the regimen of the general anaesthesia but rather by the combination of many other factors, in particular the type of operation.

Anesthesia, Inhalation↗
PubMed1999

Topical heparin for the treatment of acute superficial phlebitis secondary to indwelling intravenous catheter. A double-blind, randomized, placebo-controlled trial.

OBJECTIVE: To assess the clinical efficacy of a topical gel containing 1000 IU x g(-1) of heparin, applied three times daily for a maximal period of 7 days to patients with acute superficial phlebitis secondary to indwelling intravenous catheter. METHODS: A Double-blind, randomized, placebo-controlled study was conducted in one of the internal medicine wards of a tertiary General Hospital in Barcelona, Spain. Inpatients of both genders over 18 years of age that developed superficial phlebitis and gave informed consent were included in the study. The sample size estimation was 132 patients. Sixty-six patients were allocated to each group. There were five protocol deviations and 24 withdrawals in the intervention group, and one protocol deviation and 25 withdrawals in the control group. Consequently, 37 patients in the intervention group and 40 in the control group completed the trial. The main outcome measure was the disappearance of the symptoms and signs of superficial phlebitis. Clinical course, investigator's global impression and adverse events were also recorded. RESULTS: According to the intention-to-treat analysis, after treatment for 7 days superficial phlebitis healed in 27 of the 61 patients (44.3%) who received topical heparin, and in 17 of the 65 patients (26.1%) receiving placebo, giving a relative risk [95% confidence interval (CI)] of 1.69 (1.03-2.78). This indicates that six patients (95% CI, 3-72) have to be treated in order to induce one additional healing. The clinical course and the overall clinical impression were similar in both groups. One patient treated with topical heparin developed mild urticaria. CONCLUSION: Topical heparin is safe and effective for the treatment of superficial phlebitis secondary to indwelling intravenous catheter.

Administration, Topical↗
PubMed2003

Chromosome substitution strains: some quantitative considerations for genome scans and fine mapping.

A chromosome substitution strain (CSS) is an inbred strain in which one chromosome has been substituted from a different inbred strain by repeated backcrossing. A complete CSS set has one strain representing each chromosome against a uniform background, thus allowing genome-wide scans to be carried out for quantitative trait loci (QTLs) influencing any trait of interest. A one-way ANOVA by strain is first carried out, followed by planned comparisons using Dunnett's method. A QTL is detected and mapped to a chromosome when a significant difference is observed in a background strain vs CSS comparison. The most efficient ratio of background to CSS mice in any one comparison is 4.5:1, and the threshold for p <.05 genome-wide significance is estimated to be p =.003 to.004, a much less stringent criterion than any other mammalian mapping population. The use of false discovery rates tends to further reduce threshold stringency. Comparisons are made to the widely used conventional F(2) intercross, and both advantages and disadvantages are noted. The proportion of the trait variance due to a QTL is often much larger than the same QTL in an F(2), and the number of generations to attain fine mapping is greatly reduced. To serve as guidelines for planning experiments, methods to estimate sample sizes for QTL detection are presented for the initial genome scan and for subsequent fine mapping.

Analysis of Variance↗