Sample size determination in complex clinical trials comparing more than two groups for survival endpoints

This paper presents a sample size formula for testing the equality of kappa (> or = 2) survival distributions using the Tarone-Ware class of test statistics in the presence of non-proportional hazards, time dependent losses, non-compliance and drop-in. This method extends the derivation by Lakatos of a sample size formula for comparing two survival distributions. A sample size formula is also presented for the stratified logrank test. We describe how one can utilize these generalized formulae in calculating sample sizes and assessing power in complex multi-arm clinical trials.     

Mantel-Haenszel-type tests for testing equivalence or more than equivalence in comparative clinical trials

This paper proposes Mantel-Haenszel-type statistics for testing whether a new treatment is at least as effective as the standard treatment in comparative binomial trials. The null hypotheses considered are of a specified nonzero difference and of a ratio not equal to unity. It is shown that we may also use these tests for testing the equivalence of two treatments.     

Problems in pharmacological evaluation of patients with paroxysmal atrial fibrillation: clinical analysis of more than 100 consecutive patients

To address the problems of pharmacological evaluation in paroxysmal atrial fibrillation (PAf), we interviewed 108 consecutive patients with documented PAf regarding symptoms, frequency and trigger factors of PAf and analyzed the 24-hour ambulatory electrocardiographic monitoring (Holter monitoring) records in relation to symptoms. Twenty-nine patients were totally asymptomatic, while 79 patients were symptomatic of which 49 patients had obvious trigger factors. PAf was documented by Holter monitoring in 22 of 79 symptomatic patients. On analysis of PAf-documented 25 Holter monitoring records, the patients checked event marks as PAf in only 20 of 155 PAf episodes. Six episodes of 26 event marks that patients thought to be PAf proved to be premature atrial or ventricular contractions. Nine patients in whom PAf persisted for more than 24 hours became asymptomatic. Patients suitable for pharmacological evaluation constituted about one-fifth of the PAf patients in our consecutive study. Even with the selection of these patients, pharmacological evaluation based on symptoms is difficult because disappearance of PAf may be associated with persistent atrial fibrillation.     

Do substance abuse patients with more psychopathology receive more treatment?

The association between psychopathology at treatment entry and the amount of treatment services received was evaluated in 104 alcohol-dependent and 100 cocaine-dependent male veterans treated for 1 month in either a day hospital or inpatient program. Measures of psychopathology included the Addiction Severity Index psychiatric composite score, the presence or absence of an antisocial personality disorder diagnosis, and the total number of additional lifetime or current psychiatric diagnoses. Patients with higher admission Addiction Severity Index psychiatric composite scores received more medical, alcohol, family/social, and psychiatric services. There was also preliminary evidence that patients who received more treatment showed greater improvement 7 months after admission. The relationships between the other measures of psychopathology and treatment services failed to achieve overall statistical significance, although significant relationships were found in several individual areas.     

Long-term treatment with lansoprazole of patients with duodenal ulcer and basal acid output of more than 15 mmol/h

A great deal of quantitative information about the actomyosin interaction can be obtained from the basic Kron and Spudich in vitro motility assay provided that care is taken to obtain consistency between experiments and that the data is examined comprehensively and not selectively. From observations of filament movement under a wide variety of conditions we have formulated the hypothesis that a large number of filaments moving over a short time period is indistinguishable from fewer filaments moving over a longer sequence of frames. This has been used to devise a simple automation of filament detection procedures. A sequence of images is digitized through a frame-grabber. If successive pairs of frames are compared the program will search for and detect the new position of every filament and show its vector on screen. Velocity is calculated and shown as a frequency histogram. The program regularly detects over 100 filaments moving in each pair of frames; usually a sequence of up to 15 pairs of frames are studied yielding 500-1000 vectors in total. The algorithm cannot deal with filaments that meet, cross or divide, however, when filaments are moving less than 2 microns between frames this is only a small proportion of the whole. The program outputs fraction of filaments motile, mean velocity with standard deviation and density of filaments (filaments microns-2). A cumulative frequency histogram gives an immediate visual indication of the performance of the population of filaments. Direct comparisons show that the data produced by automatic tracking is indistinguishable from manual tracking apart from the small apparent velocity of non-mobile filaments. The detection process takes about 5 min and requires little skill or judgement. This can lead to great increases in the rate of data analysis in motility work.     

Attitudes of patients to randomised clinical trials of cancer therapy

The aim of this study was to test an instrument which might be useful for doctors in explaining the randomisation procedure to an individual patient. The sample comprised 323 patients with cancer attending for out-patient appointments and/or chemotherapy treatment in two major cancer centres in the U.K. 315 patients completed a self-report questionnaire--The Attitudes to Randomised Trials Questionnaire (ARTQ). The results show that the majority of subjects 287 (91.1%) believe that patients should be asked to take part in medical research, but only 242 (76.8%) would be prepared to take part in a study comparing two treatments. If treatment was randomised, only 141 (44.8%) would agree to participate. When given further information about the randomisation procedure, 119 (68.4%) of the 174 (55.2%) who initially said 'no' to randomisation or who were unsure, would change their minds and take part in a trial. The ARTQ discriminated between three categories of patient with the following prevailing attitudes: (a) those who seem comfortable with the concept of randomisation; (b) those with some concerns, who with fuller explanation are prepared to consider randomisation; and (c) those firmly against randomisation and participation in trials whatever information is provided. Prior knowledge of patients' attitudes might assist communication about trials and encourage more doctors to approach eligible patients.     

Statistical reporting of clinical trials with individual changes from allocated treatment

We consider clinical trials in which information is available about subjects' treatment changes after randomization. To understand whether any difference between randomized groups in the intention-to-treat analysis can be explained by such treatment changes, we need analysis strategies which take account of treatment actually received. Selection bias is then a potentially serious problem. We relate risk in a time-dependent proportional hazards model to current treatment, with treatment combinations coded in two alternative ways. To reduce selection bias, treatment history (number of treatments dropped) and baseline covariates can be added to the model. Including current risk markers would also reduce selection bias but makes interpretation difficult. The methods are illustrated using data from the British Medical Research Council (MRC) elderly hypertension trial, with time to cardiovascular death as an outcome. Results for the comparison of diuretic and beta-blocker treatment are similar in all analyses, suggesting that selection bias is small and adding support to the hypothesis that the observed treatment differences are due to the randomized treatments themselves.     

Treatment of restlessness in dying patients: more than just sedation]

The aim of this study was to evaluate the efficacy of a minimal-intervention smoking cessation program tailored to meet the needs of patients in a pneumology practice. Six-months open study was designed, multicenter, involving four pneumology practices in different Spanish cities. Smokers with or without respiratory disease who consulted a pneumologist were included. Patients were grouped according to their phase in the self-change process toward smoking cessation: precontemplation or contemplation. The level of physical dependence on nicotine was assessed using a revised version of the Fagerstr?m test. CO in exhaled air was also measured. Precontemplators were advised to quit smoking and given a booklet about smoking addiction. Contemplators were additionally given a practical guide to quitting. Advice on quitting was different for the two different phases. Smokers were reexamined twice: 8 weeks and 6 months later. We evaluated the success of the physician's intervention of encouragement to abstain (a level of CO in exhaled air [10 ppm was required]) and we recorded change of phase in the cessation process. Three hundred thirteen subjects were enrolled: 222 men (70.9%) and 91 women (29.1%). After 6 months, 40 (43%) of the precontemplators had changed phase and 21 of them (23%) had stopped smoking; 61 (28%) of the 221 contemplators had changed phase and 20 of them (9%) had quit smoking. Personalized minimal intervention in subjects with or without disease gives good results in terms of success in quitting as well as progress toward cessation.     

Rehabilitation of psychiatric patients who stayed in hospital more than one year

Fewer than one half (238) of a cohort of 489 psychiatric patients who had stayed in hospital more than one year (longstay) were still in hospital three years later. One third of these 'old' longstay patients (170) were discharged and resettled-and 81 elderly patients died. During the same three years 1971-3 a further 108 patients became (new) longstay; 57 remained at the end of the study. The discharged patients were neither readmitted unduly often, nor did they become destitute.     

Developing rat Purkinje cells are more vulnerable to alcohol-induced depletion during differentiation than during neurogenesis

This study compared the extent of cerebellar Purkinje cell depletion induced by administering alcohol to rats during two temporally distinct periods of Purkinje cell development--neurogenesis and early differentiation. One group received alcohol (5 g/kg/day) during and shortly after Purkinje cell neurogenesis (gestational days 13-18) via oral intubation of pregnant dams. A second group received alcohol (2.5 g/kg/day) during early Purkinje cell differentiation (postnatal days 4-9) via artificial rearing of pups. The two alcohol treatment protocols were designed to match the cyclic daily blood alcohol profiles of the two groups as closely as possible. Pair-fed intubated controls, artificially reared gastrostomy controls, and normally reared ad lib/suckle controls were also evaluated. Mean peak blood alcohol concentrations (BACs) were 266 mg/dl for the intubated pregnant dams and 205 mg/dl for the pups exposed postnatally. Purkinje cell profiles were counted from single, 2-microns-thick midsaggital sections on postnatal day 10. Alcohol exposure during neurogenesis resulted in no significant change in Purkinje cell profile densities. Exposure during differentiation produced significant reductions in Purkinje cell profile densities, predominantly in the early maturing regions of the vermis (lobules I-IV and IX-X). These results indicate that Purkinje cells are more vulnerable to alcohol-induced population depletion during differentiation than during neurogenesis.     

Sputum eosinophilia is more closely associated with airway responsiveness to bradykinin than methacholine in asthma

OBJECTIVE: We investigated the change in the plasma concentration of asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, in early-, mid-, and late-gestation normotensive pregnancies and in gestational age-matched preeclamptic pregnancies and compared the observed changes with changes in blood pressure. STUDY DESIGN: Blood pressure and peripheral plasma asymmetric dimethylarginine concentrations were measured in 20 nonpregnant and 145 pregnant women (33 first-trimester, 50 second-trimester, and 44 third-trimester normotensive pregnancies and 18 third-trimester pregnancies complicated by preeclampsia). In 23 normotensive pregnancies serial plasma asymmetric dimethylarginine concentrations were measured. Statistical analysis was by analysis of variance and linear regression. RESULTS: The blood pressures recorded throughout normal pregnancy were significantly lower than in nonpregnant subjects (p < 0.0001). The mean systolic, diastolic, and average blood pressures were significantly higher in the second-trimester groups than in the first-trimester groups, whereas in the third trimester average and diastolic blood pressures were significantly higher than in the second trimester. The mean (+/-SD) systolic and diastolic blood pressures in third-trimester preeclamptic patients was 157.7 +/- 11.2 and 110.9 +/- 8.5 mm Hg. The mean plasma asymmetric dimethylarginine concentration in nonpregnant women was 0.82 +/- 0.31 micromol/L (significantly higher than in normotensive pregnancy, p < 0.0001). The plasma asymmetric dimethylarginine concentration was also significantly higher in second-trimester than in first-trimester normotensive groups (respectively, 0.52 +/- 0.20 micromol/L and 0.40 +/- 0.15 micromol/L, p = 0.001) and was higher in third-trimester normotensive pregnancy 0.56 +/- 0.23 micromol/L than it was in the second trimester. The asymmetric dimethylarginine concentration in third-trimester preeclamptic patients was 1.17 +/- 0.42 micromol/L (p < 0.0001 vs normotensive third-trimester subjects). CONCLUSIONS: It is well recognized that blood pressure falls in early normal pregnancy and rises again toward term. These studies show that the early fall in blood pressure is accompanied by a significant fall in the plasma asymmetric dimethylarginine concentration. Later in pregnancy circulating concentrations increase and, when pregnancy is complicated by preeclampsia, concentrations are higher than in the nonpregnant state. Our data support a role for both asymmetric dimethylarginine and nitric oxide in the changes in blood pressure seen in both normal and preeclamptic pregnancy.     

Collection of more hematopoietic progenitor cells with large volume leukapheresis in patients with multiple myeloma

We applied reversed phase high performance liquid chromatography for globin chain synthesis analysis in screening for beta-thalassemia. The alpha/non-alpha-globin chain synthesis ratios have been determined in alpha-, beta-, and deltabeta-thalassemia carriers using the classical carboxymethyl cellulose chromatography as the reference method. Reversed phase high performance liquid chromatography is fast, accurate, and reproducible, and may be a suitable alternative for the traditional carboxymethyl cellulose chromatography.     

Correlation between clinical course and quantitative analysis of the ischemia related artery in patients with unstable angina pectoris, refractory to medical treatment. Results of two randomized trials. The European Cooperative Study Group

Patients with unstable angina, refractory to intensive medical therapy, are at high risk for developing thrombotic complications, such as recurrent ischemia, myocardial infarction and coronary occlusion during coronary angioplasty. As both platelet aggregation and/or thrombus formation play an important role in this ongoing ischemic process, a monoclonal platelet GPIIb/IIIa receptor antibody (c7E3) or thrombolytic therapy (alteplase) might be able to modify the clinical course and underlying coronary lesion morphology. To evaluate whether alteplase or c7E3 could influence the incidence of complications, we randomized 36 and 60 patients, respectively to alteplase or placebo, or c7E3 or placebo. All patients exhibited dynamic ECG changes and recurrent pain attacks, despite maximal tolerated medical therapy. Patients were randomized in both studies after initial angiography had demonstrated a culprit lesion amenable for angioplasty. After study drug infusion quantitative angiography was repeated and angioplasty performed. Recurrent ischemia during study drug infusion occurred in 5, 6, 9 and 16 patients from the alteplase, placebo, c7E3 and placebo group, respectively. Major events defined as death, myocardial infarction or urgent intervention occurred in 7, 3, 1 and 7 patients, respectively. Two patients died: one in the alteplase group and one in the placebo group from the c7E3 study. The first patient due to retroperitoneal hemorrhage, the second as a result of recurrent infarction. Qualitative angiography showed resolution of clots in the c7E3 group only, while the same group of patients showed in 20% an improvement in TIMI flow grade, without deterioration in any patient from this group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of treatment readiness on outcomes of two pharmacotherapy trials for cocaine abuse among methadone-maintained patients.

Secondary analyses were conducted on data from 2 pharmacotherapy trials for cocaine dependence in methadone-maintained patients to explore factors potentially associated with treatment readiness. One trial enrolled current cocaine users, and the other enrolled newly abstinent patients. Newly abstinent patients showed evidence of treatment readiness in that they submitted fewer cocaine-positive urine specimens during the trial and reported more aversion than craving in response to cues, greater self-efficacy in high-risk situations, greater confidence in treatment, and less depression. They identified less with an "addict" self-schema and were motivated to stop using cocaine because of perceived consequences to health and freedom and a desire for self-control. The influence of treatment readiness in pharmacotherapy trials is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subjective experience and attitudes towards participation in clinical trials among patients with anxiety disorders

Newly recognized rat parvovirus (rat orphan parvovirus: ROPV) was examined for viral excretion and persistence in infected rats, and also for infectivity to mice and hamsters. The virus appeared to replicate mainly in lymphoid or hematopoietic tissues, and was detected in feces, urine and oropharynx of the infected rats at 1 to 4 weeks postinfection. The infective virus was also detected in peripheral leukocytes and various tissues at an acute phase of infection, and decreased in every tissue at 8 weeks postinfection. Viral DNA, however, was persistent in lymphoid tissues at least up to 24 weeks postinfection. When the virus was inoculated to mice and hamsters, no evidence of viral production and antibody response was demonstrated. ROPV is assumed to be a variant of the known rat parvovirus which resulted to alter cell tropism and persist in lymphoid or hematopoietic tissues, in order to escape from host immune system.     

Issues in extrapolating from clinical trials to clinical practice and outcomes

Extrapolation of clinical trial results to clinical practice requires consideration of whether the trial patients were representative of clinical practice, whether the trial therapy studied was optimal, whether the sample size was adequate, and the impact of adjunctive treatments. In thrombolytic trials in particular, regional variations in attitudes to coronary angiography may have affected outcomes. Clinical trial results need to be interpreted in the light of the cost effectiveness of the application. The assessment of clinical outcomes depends on interplay between the structure and process of care, patient factors and chance. Large standardised databases are necessary to assess clinical practice and outcomes.     

Isolation of Actinomyces viscosus from two patients with clinical infections

The isolation of Actinomyces viscosus from two patients is described. One was a case of multiple myeloma, the organism being found on blood culture; the other was a patient with a submandibular abscess. These are believed to be the first such isolations of A. viscosus in this country.     

Not more symptoms with mefloquine use than with other drugs in malaria prophylaxis

This prospective study evaluates the practical utility of a special plastic syringe for collecting arterial blood samples for gasometry, comparing it to a glass syringe and a conventional plastic one, in 120 patients who came to our hospital for arterial blood analysis for a variety of reasons. The patients were randomly assigned to one of three groups according to type of syringe assigned. Technicians with experience in the technique prepared the syringes and collected the arterial blood samples after providing local anesthesia. The results showed that the special plastic syringe took less time (p < 0.05) to prepare than did the glass or conventional plastic ones. The differences were quite small, however, in absolute terms, with the special syringe requiring 17 seconds less than the glass syringe and 6 seconds less than the plastic one; the practical importance is therefore slight. No other advantages of the special syringe were observed. No patient required more than one puncture to obtain a valid arterial blood sample, the extraction times (time between arterial puncture until end of process) were similar in the three groups of patients, and the presence of post-puncture hematoma was rare in all groups. There were no differences in level of pain reported (on an analog scale) and the subjective quality of the radial pulse wave was good and similar in all three groups. In conclusion, these results show that use of the special syringe offers no important practical advantages for experienced technicians that would justify the higher price. In fact, as the conventional plastic syringes are cheaper, disposable and similarly effective in expert hands, our results suggest that their routine use for collecting arterial blood gas samples can help improve the cost-benefit ratio for a common procedure in pulmonary function units.