Blood-pressure targets in patients with recent lacunar stroke: the SPS3 randomised trial.

BACKGROUND: Lowering of blood pressure prevents stroke but optimum target levels to prevent recurrent stroke are unknown. We investigated the effects of different blood-pressure targets on the rate of recurrent stroke in patients with recent lacunar stroke. METHODS: In this randomised open-label trial, eligible patients lived in North America, Latin America, and Spain and had recent, MRI-defined symptomatic lacunar infarctions. Patients were recruited between March, 2003, and April, 2011, and randomly assigned, according to a two-by-two multifactorial design, to a systolic-blood-pressure target of 130-149 mm Hg or less than 130 mm Hg. The primary endpoint was reduction in all stroke (including ischaemic strokes and intracranial haemorrhages). Analysis was done by intention to treat. This study is registered with ClinicalTrials.gov, number NCT 00059306. FINDINGS: 3020 enrolled patients, 1519 in the higher-target group and 1501 in the lower-target group, were followed up for a mean of 3·7 (SD 2·0) years. Mean age was 63 (SD 11) years. After 1 year, mean systolic blood pressure was 138 mm Hg (95% CI 137-139) in the higher-target group and 127 mm Hg (95% CI 126-128) in the lower-target group. Non-significant rate reductions were seen for all stroke (hazard ratio 0·81, 95% CI 0·64-1·03, p=0·08), disabling or fatal stroke (0·81, 0·53-1·23, p=0·32), and the composite outcome of myocardial infarction or vascular death (0·84, 0·68-1·04, p=0·32) with the lower target. The rate of intracerebral haemorrhage was reduced significantly (0·37, 0·15-0·95, p=0·03). Treatment-related serious adverse events were infrequent. INTERPRETATION: Although the reduction in stroke was not significant, our results support that in patients with recent lacunar stroke, the use of a systolic-blood-pressure target of less than 130 mm Hg is likely to be beneficial. FUNDING: National Institutes of Health-National Institute of Neurological Disorders and Stroke (NIH-NINDS).

The Levels of Inflammatory Markers in the Treatment of Stroke study (LIMITS): inflammatory biomarkers as risk predictors after lacunar stroke.

BACKGROUND: Inflammation is increasingly recognised as playing a central role in atherosclerosis, and peripheral blood markers of inflammation have been associated with incident and recurrent cardiac events. The relationship of these potentially modifiable risk markers to prognosis after ischaemic stroke is less clear. The Levels of Inflammatory Markers in the Treatment of Stroke (LIMITS) study will address hypotheses related to the role of inflammatory markers in secondary stroke prevention in an efficient manner using the well-established framework of the Secondary Prevention of Small Subcortical Strokes (SPS3) trial (NCT00059306). METHODS: SPS3 is an ongoing Phase III multicentre secondary prevention trial focused on preventing recurrent stroke in patients with small vessel ischaemic stroke, or lacunes. In SPS3, patients are assigned in a factorial design to aspirin vs. aspirin plus clopidogrel, and to usual vs. aggressive blood pressure targets. The purpose of LIMITS is to determine whether serum levels of inflammatory markers - including high-sensitivity C-reactive protein, serum amyloid A, CD40 ligand, and monocyte chemoattractant protein-1 - predict recurrent stroke and other vascular events among lacunar stroke patients. The project will also determine whether these markers predict which people will respond best to dual antiplatelet therapy with clopidogrel and aspirin, as well the relationship to cognitive function. ANALYSIS: plan Multivariable Cox proportional hazard regression modeling will be used to estimate hazard ratios for the effect of marker levels on risk of recurrent stroke and other outcomes after adjusting for additional potential risk factors, including age, gender, ethnicity, treatment arm, and traditional stroke risk factors. Interactions between marker levels and treatment assignment for both arms of the SPS3 study will be assessed. Observations will be censored at the time of last follow-up visit. CONCLUSIONS: LIMITS represents an efficient approach to the identification of novel inflammatory biomarkers for use in risk prediction and treatment selection in patients with small vessel disease.

Gender-specific correlations of plasminogen activator inhibitor-1 and tissue plasminogen activator levels with cardiovascular disease-related traits.

BACKGROUND: The purpose of this study was to examine the correlations between plasma levels of plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (t-PA) and cardiovascular disease-related traits in a general population and whether these correlations differed between females and males. METHODS: Plasma PAI-1 and t-PA antigen levels and C-reactive protein (CRP), HDL-cholesterol, triglycerides, total cholesterol, systolic blood pressure, diastolic blood pressure, urinary albumin excretion, and glucose were measured in the population-based PREVEND study in Groningen, the Netherlands (n = 2527). RESULTS: Except for CRP and total cholesterol levels, all traits were significantly different between gender (P < 0.001). PAI-1 levels were correlated with all measured cardiovascular disease-related traits (P < 0.01) in both females and males. Except for urinary albumin excretion, similar results, albeit less significant, were found for t-PA levels. Age-adjusted correlations between PAI-1 and CRP, triglycerides, total cholesterol, systolic blood pressure, and diastolic blood pressure differed significantly between females and males (P < 0.01). Many of the gender differences were predominantly present between premenopausal females and males. CONCLUSION: PAI-1 and t-PA levels were correlated with cardiovascular disease-related traits in subjects obtained from the general population and several of these correlations differed across gender. The correlations found in the present study suggest the presence of coordinated patterns of cardiovascular risk factors and indicate which traits might influence PAI-1 and t-PA levels and thereby provide a framework and potential tool for therapeutic intervention to reduce thromboembolic events in the general population.

A randomized double-blind placebo-controlled clinical trial of a product containing ephedrine, caffeine, and other ingredients from herbal sources for treatment of overweight and obesity in the absence of lifestyle treatment.

OBJECTIVE: To evaluate the efficacy and side effects of an herbal formulation to promote weight loss, as compared to placebo. DESIGN: 12-week multicenter double-blind, placebo-controlled, randomized parallel groups design. Study conducted at three clinical sites in New York State. Subjects were randomized to receive either the 'active' product or a 'placebo' supplement for 12 weeks. Minimal steps were taken to influence lifestyle changes with regard to diet or exercise. SUBJECTS: 102 overweight/obese (30

Caloric restriction and body weight independently affect longevity in Wistar rats.

OBJECTIVE: To evaluate the independent effects of caloric restriction (CR) and body weight (BW) on mortality rate (MR) and the extent to which BW may mediate the effect of CR on MR. DESIGN AND SUBJECTS: Data were from the Biosure Study, a randomized, controlled, prospective intervention study of diet regimens in 1200 Wistar rats. Animals were followed until they died spontaneously, were euthanized because of illness, or reached age 30 months. STATISTICAL ANALYSIS: Cox regression was performed to evaluate the effects of CR and BW on MR. Bootstrap procedures were used to test the contribution of BW to the effect of CR on MR. RESULTS: CR initiated after age 13 weeks decreased the rate of subsequent mortality. The MR increased with higher BW in early adulthood (21 weeks) and this effect persisted even after adjustment for CR. After adjustment for BW in early adulthood, we did not find a similar relation between mortality and BW in late adulthood (105 weeks). Mediation analysis indicated that low BW associated with CR appeared to mediate some of the mortality-reducing effects of CR, but CR clearly had effects independent of BW. The reductions in BW appeared to account for approximately 11% of the effect of CR. CONCLUSION: CR and BW have independent effects on MR in Wistar rats. BW may mediate a small part of the CR effects on MR.

Modern statistical methods for handling missing repeated measurements in obesity trial data: beyond LOCF.

This paper brings together some modern statistical methods to address the problem of missing data in obesity trials with repeated measurements. Such missing data occur when subjects miss one or more follow-up visits, or drop out early from an obesity trial. A common approach to dealing with missing data because of dropout is 'last observation carried forward' (LOCF). This method, although intuitively appealing, requires restrictive assumptions to produce valid statistical conclusions. We review the need for obesity trials, the assumptions that must be made regarding missing data in such trials, and some modern statistical methods for analysing data containing missing repeated measurements. These modern methods have fewer limitations and less restrictive assumptions than required for LOCF. Moreover, their recent introduction into current releases of statistical software and textbooks makes them more readily available to the applied data analyses.

Overestimation of genetic risks owing to small sample sizes in cardiovascular studies.

We sought evidence of publication bias to explain conflicting findings in studies of angiotensin-converting enzyme deletion polymorphism (ACE D) and glycoprotein IIIa PlA2 (PLA2) polymorphism and the risk of myocardial infarction. Factor 5 Leiden (F5L), a well-established thrombotic risk factor, served as an internal comparison. We conducted systematic reviews of published studies involving ACE D, PLA2, F5L and relevant outcomes, searching medline (January 1990 through February, 2001), bibliographies, and meta-analyses. Random effects pooled odds ratios (95% confidence interval) for cardiovascular outcomes were as follows: PLA2 (n = 13,167 subjects): 1.13 (1.02, 1.26); ACE D (n = 42,140 subjects): 1.22 (1.11, 1.35); and F5L (n = 27,277 subjects): 4.43 (3.65, 5.38). However, funnel plots of ACE D and PLA2, but not F5L, showed an inverse relationship between sample size and odds ratios for ACE D (p = 0.02) and PLA2 (p = 0.04) but not F5L (p = 0.65) by Egger's test for potential publication bias. Despite research-based genotyping of over 50,000 subjects, the overall risk for myocardial infarction as a result of PLA2 and ACE D remains doubtful. Our study provides a clear example of how publication of underpowered studies can spuriously implicate polymorphisms as genetic risk factors.

Improving the detection of simulated masses in mammograms through two different image-processing techniques.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether contrast-limited adaptive histogram equalization (CLAHE) or histogram-based intensity windowing (HIW) improves the detection of simulated masses in dense mammograms. MATERIALS AND METHODS: Simulated masses were embedded in portions of mammograms of patients with dense breasts; the mammograms were digitized at 50 microm per pixel, 12 bits deep. In two different experiments, images were printed both with no processing applied and with related parameter settings of two image-processing methods. A simulated mass was embedded in a realistic background of dense breast tissue, with its position varied. The key variables in each trial included the position of the mass, the contrast levels of the mass relative to the background, and the selected parameter settings for the image-processing method. RESULTS: The success in detecting simulated masses on mammograms with dense backgrounds depended on the parameter settings of the algorithms used. The best HIW setting performed better than the best fixed-intensity window setting and better than no processing. Performance with the best CLAHE settings was no different from that with no processing. In the HIW experiment, there were no significant differences in observer performance between processing conditions for radiologists and nonradiologists. CONCLUSION: HIW should be tested in clinical images to determine whether the detection of masses by radiologists can be improved. CLAHE processing will probably not improve the detection of masses on clinical mammograms.

Alterations in lipoxygenase and cyclooxygenase-2 catalytic activity and mRNA expression in prostate carcinoma.

Recent studies in prostate tissues and especially cell lines have suggested roles for arachidonic acid (AA) metabolizing enzymes in prostate adenocarcinoma (Pca) development or progression. The goal of this study was to more fully characterize lipoxygenase (LOX) and cyclooxygenase-2 (COX-2) gene expression and AA metabolism in benign and malignant prostate using snap-frozen tissues obtained intraoperatively and mRNA analyses and enzyme assays. Formation of 15-hydroxyeicosatetraenoic acid (15-HETE) was detected in 23/29 benign samples and 15-LOX-2 mRNA was detected in 21/25 benign samples. In pairs of pure benign and Pca from the same patients, 15-HETE production and 15-LOX-2 mRNA were reduced in Pca versus benign in 9/14 (P=.04) and 14/17 (P=.002), respectively. Under the same conditions, neither 5-HETE nor 12-HETE formation was detectable in 29 benign and 24 tumor samples; with a more sensitive assay, traces were detected in some samples, but there was no clear association with tumor tissue. COX-2 mRNA was detected by nuclease protection assay in 7/16 benign samples and 5/16 tumors. In benign and tumor pairs from 10 patients, COX-2 was higher in tumor versus benign in only 2, with similar results by in situ hybridization. Paraffin immunoperoxidase for COX-2 was performed in whole mount sections from 87 additional radical prostatectomy specimens, with strong expression in ejaculatory duct as a positive control and corroboration with in situ hybridization. No immunostaining was detected in benign prostate or tumor in 45% of cases. Greater immunostaining in tumor versus benign was present in only 17% of cases, and correlated with high tumor grade (Gleason score 8 and 9 vs. 5 to 7). In conclusion, reduced 15-LOX-2 expression and 15-HETE formation is the most characteristic alteration of AA metabolism in Pca. Increased 12-HETE and 5-HETE formation in Pca were not discernible. Increased COX-2 expression is not a typical abnormality in Pca in general, but occurs in high-grade tumors.

Clinical under staging of high risk nonmuscle invasive urothelial carcinoma treated with radical cystectomy.

PURPOSE: The role of radical cystectomy in patients with nonmuscle invasive urothelial carcinoma of the bladder remains controversial. The risk of overtreatment must be balanced against the potential benefit of aggressive therapy. We reviewed our results in these patients with a particular emphasis on clinical under staging. MATERIALS AND METHODS: We reviewed the records of 214 consecutive patients who underwent radical cystectomy for urothelial carcinoma between April 1995 and August 1999, focusing on those with nonmuscle invasive, stages T1 or less disease. We assessed clinical and pathological data as well as outcomes based on pathological disease extent. RESULTS: A total of 78 patients (36%) underwent radical cystectomy for clinical stages T1 or less disease. Indications included disease refractory to intravesical therapy in 29 cases (37%), pathological findings reflective of high grade stage T1 or multifocal disease in 26 (33%), radiographic suspicion of invasive disease in 15 (20%) and severe symptoms in 8 (10%). Cancer was clinically under staged with stages pT2 or greater disease in 31 patients (40%) according to final pathology results. Under staging was most pronounced in the 10 patients (67%) with suspicious radiography and in the 18 (64%) with absent muscle in the biopsy specimen. Of the 78 patients with pathological stages pT1 disease or less 98% had no evidence of disease compared to 65% with stages pT2 or greater disease (p <0.01). CONCLUSIONS: Despite the intent to perform early cystectomy a significant percent of patients harbored occult muscle invasive and/or metastatic disease. In clinical and pathological, superficial stages T1 or less cases disease-free survival was excellent. Due to these results, the selection of high risk superficial transitional cell carcinoma cases for continued bladder sparing treatment should include uninvolved muscle on biopsy and absent radiographic suspicion of invasion.

Controlling test size while gaining the benefits of an internal pilot design.

To compensate for a power analysis based on a poor estimate of variance, internal pilot designs use some fraction of the planned observations to reestimate error variance and modify the final sample size. Ignoring the randomness of the final sample size may bias the final variance estimate and inflate test size. We propose and evaluate three different tests that control test size for an internal pilot in a general linear univariate model with fixed predictors and Gaussian errors. Test 1 uses the first sample plus those observations guaranteed to be collected in the second sample for the final variance estimate. Test 2 depends mostly on the second sample for the final variance estimate. Test 3 uses the unadjusted variance estimate and modifies the critical value to bound test size. We also examine three sample-size modification rules. Only test 2 can control conditional test size, align with a modification rule, and provide simple power calculations. We recommend it if the minimum second (incremental) sample is at least moderate (perhaps 20). Otherwise, the bounding test appears to have the highest power in small samples. Reanalyzing published data highlights some advantages and disadvantages of the various tests.

Effect of vagal cooling on the counterregulatory response to hypoglycemia induced by a low dose of insulin in the conscious dog.

We previously demonstrated, using a nerve-cooling technique, that the vagus nerves are not essential for the counterregulatory response to hypoglycemia caused by high levels of insulin. Because high insulin levels per se augment the central nervous system response to hypoglycemia, the question arises whether afferent nerve fibers traveling along the vagus nerves would play a role in the defense of hypoglycemia in the presence of a more moderate insulin level. To address this issue, we studied two groups of conscious 18-h-fasted dogs with cooling coils previously placed on both vagus nerves. Each study consisted of a 100-min equilibration period, a 40-min basal period, and a 150-min hypoglycemic period. Glucose was lowered using a glycogen phosphorylase inhibitor and a low dose of insulin infused into the portal vein (0.7 mU.kg(-1) min(-1)). The arterial plasma insulin level increased to 15 +/- 2 microU/ml and the plasma glucose level fell to a plateau of 57 +/- 3 mg/dl in both groups. The vagal cooling coils were perfused with a 37 degrees C (SHAM COOL; n = 7) or a -20 degrees C (COOL; n = 7) ethanol solution for the last 90 min of the study to block parasympathetic afferent fibers. Vagal cooling caused a marked increase in the heart rate and blocked the hypoglycemia-induced increase in the arterial pancreatic polypeptide level. The average increments in glucagon (pg/ml), epinephrine (pg/ml), norepinephrine (pg/ml), cortisol (microg/dl), glucose production (mg.kg(-1). min(-1)), and glycerol (micromol/l) in the SHAM COOL group were 53 +/- 9, 625 +/- 186, 131 +/- 48, 4.63 +/- 1.05, -0.79 +/- 0.24, and 101 +/- 18, respectively, and in the COOL group, the increments were 39 +/- 7, 837 +/- 235, 93 +/- 39, 6.28 +/- 1.03 (P < 0.05), -0.80 +/- 0.20, and 73 +/- 29, respectively. Based on these data, we conclude that, even in the absence of high insulin concentrations, afferent signaling via the vagus nerves is not required for a normal counterregulatory response to hypoglycemia.

Prediction of tumour volume and pathological stage in radical prostatectomy specimens is not improved by taking more prostate needle-biopsy cores.

OBJECTIVE: To determine what, if any, additional prognostic information is available from the prostate needle biopsy by comparing the number of biopsy cores obtained with the pathology assessed from the radical retropubic prostatectomy (RRP) specimen. PATIENTS AND METHODS: The results from 135 consecutive patients who underwent RRP at a single institution were reviewed. Needle biopsy information (number of cores, percentage of positive cores, laterality of the positive cores, and Gleason sum) were compared with the pathological data of the RRP specimen, including stage, Gleason sum and tumour volume. Patients were further stratified into those with six or fewer cores (96 men) or more than six cores (39 men). Clinical data, including biopsy information and pathological findings, were compared using univariate and multivariate models. RESULTS: Overall, univariate analysis showed that the total prostate-specific antigen (PSA) level, number of positive cores, bilateral positive cores and percentage of positive cores were directly correlated with tumour volume (P=0.01). Also, PSA and percentage of positive cores were directly correlated with extracapsular extension (P=0.008 and P=0.01, respectively). In the multivariate model, the most important independent predictors of RRP tumour volume and pathological stage were the preoperative PSA level and percentage of cancer in the biopsy (P<0.01). There was no significant relationship between the number of cores obtained and the predicted pathology of the RRP specimen. There were no differences in the number of positive cores, bilateral positive cores or percentage tumour in the cores between men with more or less than six biopsies. In men with more than six core biopsies, there was no significant increase in prognostic information for tumour volume and extracapsular extension, or a correlation between the Gleason sum on biopsy and the RRP specimen. Taking more than six biopsies did not result in a significantly greater detection of potentially indolent tumours (defined as a tumour volume of <0.5 mL). CONCLUSIONS: While taking more prostate needle biopsy cores seems to improve the detection of prostate cancer, there appears to be no major improvement in prognostic information over that gained from traditional sextant biopsies. Furthermore, the results suggest that the percentage of positive cores is the best predictor of both pathological stage and tumour volume, from among the information readily available from prostate needle biopsy. Given the variability in the number of cores obtained for diagnosis in clinical practice, these results add credence to the use of the percentage of positive cores in the biopsy set, with known predictors such as PSA and Gleason score, into future models that attempt to predict tumour biology.

Effect of hepatic denervation on the counterregulatory response to insulin-induced hypoglycemia in the dog.

Our aim was to determine whether complete hepatic denervation would affect the hormonal response to insulin-induced hypoglycemia in dogs. Two weeks before study, dogs underwent either hepatic denervation (DN) or sham denervation (CONT). In addition, all dogs had hollow steel coils placed around their vagus nerves. The CONT dogs were used for a single study in which their coils were perfused with 37 degrees C ethanol. The DN dogs were used for two studies in a random manner, one in which their coils were perfused with -20 degrees C ethanol (DN + COOL) and one in which they were perfused with 37 degrees C ethanol (DN). Insulin was infused to create hypoglycemia (51 +/- 3 mg/dl). In response to hypoglycemia in CONT, glucagon, cortisol, epinephrine, norepinephrine, pancreatic polypeptide, glycerol, and hepatic glucose production increased significantly. DN alone had no inhibitory effect on any hormonal or metabolic counterregulatory response to hypoglycemia. Likewise, DN in combination with vagal cooling also had no inhibitory effect on any counterregulatory response except to reduce the arterial plasma pancreatic polypeptide response. These data suggest that afferent signaling from the liver is not required for the normal counterregulatory response to insulin-induced hypoglycemia.

Reduced 15-lipoxygenase-2 immunostaining in prostate adenocarcinoma: correlation with grade and expression in high-grade prostatic intraepithelial neoplasia.

Arachidonic acid (AA) metabolites are implicated in the oncogenesis of several tumors, including prostate cancer. 15-Lipoxygenase-2 (15-LOX-2) is a novel AA-metabolizing enzyme with a limited tissue distribution, which includes prostate, lung, skin, and cornea. Previous studies have shown that 15-LOX-2 is present in benign prostate secretory cells and reduced in prostate adenocarcinoma and that production of the 15-LOX-2 metabolite 15S-hydroxyeicosatetraenoic acid is reduced in malignant compared with benign prostate. The objective of this study was to determine the frequency with which 15-LOX-2 immunostaining is reduced in prostate carcinoma and to correlate reduced expression with tumor differentiation (grade) and other pathologic parameters in radical prostatectomy specimens. Paraffin immunoperoxidase with a polyclonal antibody specific for 15-LOX-2 was performed on tumors and benign portions from 70 cases, and the percentage of tumor immunostaining for 15-LOX-2 was assessed. Whereas uniform 15-LOX-2 immunostaining was observed in secretory cells of benign glands, it was markedly reduced or absent in most adenocarcinomas: 23 of 70 tumors showed completely absent 15-LOX-2 immunostaining, and 45 of 70 cases showed negative immunostaining in more than 50% of the tumor. The extent of reduced 15-LOX-2 immunostaining correlated with tumor differentiation, with retained expression particularly in Gleason score 5 tumors versus a significant reduction of 15-LOX-2 in higher-grade tumors (mean +/- SD tumor 15-LOX-2 positive: Gleason score 5 = 67%+/-30%, Gleason score 6 = 16%+/-30%, Gleason score 7 = 23%+/-28%, Gleason score > or =8 = 41%+/-46%). In 16 cases with multifocal tumors or different foci of the same tumor with different grades, the higher-grade foci had significantly reduced 15-LOX-2 expression compared with the lower-grade foci. In peripheral zone tumors without complete loss of 15-LOX-2 expression, there was a significant inverse relationship between 15-LOX-2 immunostaining and tumor volume. There was not a significant correlation between 15-LOX-2 immunostaining and serum PSA or pathologic stage. In a subset of 27 cases, 15-LOX-2 expression in high-grade prostatic intraepithelial neoplasia (HGPIN) glands was significantly reduced compared with benign glands. These data show that in contrast to the uniform expression of 15-LOX-2 in differentiated secretory cells of benign prostate, reduced 15-LOX-2 is a common alteration in prostate carcinoma, and this correlates with tumor cell differentiation. That reduced expression is seen in HGPIN suggests that this may be an early alteration in carcinoma development.

Effect of display luminance on the feature detection rates of masses in mammograms.

Our purpose in this study was to determine the importance of the luminance range of the display system for the detection of simulated masses in mammograms. Simulated masses were embedded in selected portions (512 x 512 pixels) of mammograms digitized at 50 micro pixels, 12 bits deep. The masses were embedded in one of four quadrants in the image. An observer experiment was conducted in which the observer's task was to determine in which quadrant the mass is located. The key variables involved in each trial included the position of the mass, the contrast level of the mass, and the luminance of the display. The contrast of the mass with respect to the background was fixed to one of four selected contrast levels. The digital images were printed to film, and displayed on a mammography lightbox. The display luminance was controlled by placing neutral density films between the laser printed films of mammographic backgrounds and the lightbox. The resulting maximum luminances examined in this study ranged from 34 cd/m2 to 2056 cd/m2. Twenty observers viewed 80 different images (20 observations at each of 4 different mass contrast levels) under each of the 5 luminance conditions for a total of 800 independent observations per observer. An analysis of variance yielded no statistically significant correlation between the luminance range of the display and the feature detection rate of the simulated masses in mammograms. However, the performance of the lower luminance display systems (less than 300 cd/m2), may be reduced due to the high levels of ambient light found in many reading environments.

Exact test size and power of a Gaussian error linear model for an internal pilot study.

Wittes and Brittain recommended using an 'internal pilot study' to adjust sample size. The approach involves five steps in testing a general linear hypothesis for a general linear univariate model, with Gaussian errors. First, specify the design, hypothesis, desired test size, power, a smallest 'clinically meaningful' effect, and a speculated error variance. Second, conduct a power analysis to choose provisionally a planned sample size. Third, collect a specified proportion of the planned sample as the internal pilot sample, and estimate the variance (but do not test the hypothesis). Fourth, update the power analysis with the variance estimate to adjust the total sample size. Fifth, finish the study and test the hypothesis with all data. We describe methods for computing exact test size and power under this scenario. Our analytic results agree with simulations of Wittes and Brittain. Furthermore, our exact results apply to any general linear univariate model with fixed predictors, which is much more general than the two-sample t-test considered by Wittes and Brittain. In addition, our results allow for examination of the impact on test size of internal pilot studies for more complicated designs in the framework of the general linear model. We examine the impact of (i) small samples, (ii) allowing the planned sample size to decrease, (iii) the choice of internal pilot sample size, and (iv) the maximum allowable size of the second sample. All affect test size, power and expected total sample size. We present a number of examples including one that uses an internal pilot study in a three-group analysis of variance.

Comparison of computer workstation with light box for detecting setup errors from portal images.

PURPOSE: Observer studies were conducted to test the hypothesis that radiation oncologists using a computer workstation for portal image analysis can detect setup errors at least as accurately as when following standard clinical practice of inspecting portal films on a light box. METHODS AND MATERIALS: In a controlled observer study, nine radiation oncologists used a computer workstation, called PortFolio, to detect setup errors in 40 realistic digitally reconstructed portal radiograph (DRPR) images. PortFolio is a prototype workstation for radiation oncologists to display and inspect digital portal images for setup errors. PortFolio includes tools for image enhancement; alignment of crosshairs, field edges, and anatomic structures on reference and acquired images; measurement of distances and angles; and viewing registered images superimposed on one another. The test DRPRs contained known in-plane translation or rotation errors in the placement of the fields over target regions in the pelvis and head. Test images used in the study were also printed on film for observers to view on a light box and interpret using standard clinical practice. The mean accuracy for error detection for each approach was measured and the results were compared using repeated measures analysis of variance (ANOVA) with the Geisser-Greenhouse test statistic. RESULTS: The results indicate that radiation oncologists participating in this study could detect and quantify in-plane rotation and translation errors more accurately with PortFolio compared to standard clinical practice. CONCLUSIONS: Based on the results of this limited study, it is reasonable to conclude that workstations similar to PortFolio can be used efficaciously in clinical practice.

Effects of inhibition of lipoxygenase and guanylate cyclase on human neutrophil responses to formyl peptide and granulocyte-macrophage colony-stimulating factor.

Human neutrophils were activated by the bacterial chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (fMLP) to produce superoxide (O2-) and to release the primary granule enzyme beta-glucuronidase and the predominantly secondary granule enzyme lysozyme. Pretreatment with granulocyte-macrophage colony-stimulating factor (GM-CSF) increased the secretion of all three substances upon addition of fMLP. The augmentation by GM-CSF was significantly attenuated by the 5-lipoxygenase inhibitor AA861 and by the guanylate cyclase inhibitor LY83583. The secretion induced by fMLP alone was much less affected by either of the two inhibitors. AA861 inhibited leukotriene B4 production in neutrophils primed with GM-CSF and stimulated with fMLP, and LY83583 inhibited GM-CSF-evoked increases of 3',5'-guanosine monophosphate. The data suggest that activation of lipoxygenase and guanylate cyclase is not critical to the fMLP stimulation pathway, but they may be important components of the pathway by which GM-CSF augments neutrophil responses to fMLP. However, AA861 and LY83583 may have important actions in addition to inhibition of 5-lipoxygenase and guanylate cyclase.