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PubMed2003

Atrial arrhythmia burden as an endpoint in clinical trials: is it the best surrogate? Lessons from a multicenter defibrillator trial.

Therapies to treat atrial tachyarrhythmias need to be evaluated in controlled, randomized clinical trials in order to optimize patient outcomes. If the maintenance of sinus rhythm is the ultimate goal, then atrial tachyarrhythmia burden may serve as a useful endpoint. Atrial tachyarrhythmia burden is defined as the total duration of all atrial tachyarrhythmias divided by the follow-up time and includes asymptomatic as well as symptomatic episodes. The measurement of atrial tachyarrhythmia burden is more practical now than in the past because of the availability of implantable devices capable of monitoring atrial tachyarrhythmia episodes. The advantage of burden over other endpoints is that it is not subject to investigator bias and it does not have the sampling error associated with episodic rhythm monitoring or the monitoring of patient symptoms. The use of burden as a surrogate endpoint for clinical outcome facilitates the demonstration of a biological effect of a therapy on the triggers or substrates responsible for the arrhythmia. Therapies that reduce burden can then be further studied to assess more traditional endpoints. A recent multicenter trial examined the effect of device-based atrial therapies on burden in patients receiving an implantable cardioverter defibrillator (Medtronic 7250 Jewel AF) to treat ventricular tachyarrhythmias. Patients were randomized to 3-month periods of atrial therapies "ON" or "OFF" and subsequently crossed over. The atrial therapies resulted in a reduction of atrial tachyarrhythmia burden from a mean of 58.5 hours/month to 7.8 hours/month (P = 0.007). Based on the evidence of a biological effect of the atrial therapies (burden reduction) studies to determine of the effects of AT/AF prevention and termination algorithms on morbidity and quality of life in ICD recipients are underway.

Atrial Fibrillation↗
PubMed2000

Comparison of endothelial cell density estimated by contact and non-contact specular microscopy.

PURPOSE: To compare a contact and a non-contact specular microscope in the determination of endothelial cell density. SUBJECTS AND METHODS: One hundred and twenty-one eyes from 70 patients who had undergone various degrees of photorefractive keratectomy for myopia were included. The endothelium was imaged by contact (Konan Clinical Specular Microscope) and non-contact (Topcon SP-1000) specular microscopy and the endothelial cell density estimated. RESULTS: The average endothelial cell density achieved by the contact specular microscope was 3011+/-298 cells/mm2 (mean+/-SD, n=121) and by the non-contact specular microscope 3015+/-265 cells/mm2 (n= 121). The difference in endothelial cell density between the contact and the non-contact specular microscope (contact minus non-contact) was -4+/-175 cells/mm2 (t=0.26, 2p>0.05 in a paired t-test). The sampling error on the estimated endothelial cell density was 76 cells/mm2 for the contact specular microscope and 74 cells/mm2 for the non-contact specular microscope. CONCLUSION: The average endothelial cell density and the precision of the measuring technique were similar for the contact and the non-contact specular microscope. Furthermore, the endothelial cell densities estimated by the two instruments at various values of anterior central corneal refractive power and central corneal thickness were similar. The two instruments can be used interchangeably.

Adult↗
PubMed1989

Age-related differences in employee absenteeism: a meta-analysis.

Meta-analyses were performed on 34 samples that included correlations of the age and employee absenteeism relationship. Samples were categorized into 2 groups for voluntary absenteeism and involuntary absenteeism based on the frequency index and the time-lost index, respectively. Results indicated that both voluntary and involuntary absence are inversely related to age. Unexplained variance remained for each of the absence measures after variance due to sampling error and measurement unreliability was statistically estimated. Work demand was negatively associated with age, but not in the expected direction. Work demand did not moderate the age-absence relationship for either voluntary or involuntary absence. Sex moderated the relationship between age and voluntary absenteeism only. For men, the relationships were negative; for women, they did not differ significantly from 0. Implications for research and human resource management practices regarding aging and absenteeism are discussed.

Absenteeism↗
PubMed1995

Comment on Black's (1993) article, "comparing genuine and simulated suicide notes: a new perspective".

The recent article by Stephen T. Black (1993) comparing genuine suicide notes with simulated notes is examined here. This article corrected a sampling error made in the original study by E. S. Shneidman and N. Farberow (1957), but Black's design suffers from theoretical and methodological problems that render it uninterpretable: First, no theoretical background is elaborated, and no hypotheses are offered. Second, no constructs are operationalized, and no predictions are tested. In the present article, the operational design is critiqued, and then it is suggested that the study of suicide notes in this fashion should cease.

Humans↗
PubMed1991

Age effects may be global, not local: comment on Fisk and Rogers (1991)

A series of analyses of variance on target search times allowed Fisk and Rogers (1991) to reject the null hypothesis that age had a uniform, additive effect across search conditions. It does not, however, follow that age affected some conditions in an exceptional way, as Fisk and Rogers concluded. Age may have had a uniform but nonadditive effect across conditions. In this article, it is shown that age had a uniform linear, or perhaps slightly curvilinear, effect on search times. This "null hypothesis" adequately accounted for the age effects in all 27 search conditions. Indeed, it accounted for the age effects in 107 conditions abstracted from other visual search studied and for the age effects in 154 conditions abstracted from a miscellaneous collection of nonsearch processing-time studies. The only variation in age outcomes across studies was consistent with sampling error, given the known variance in response times. It is concluded that age is experienced as a generalized slowing of the central nervous system uniformly affecting all information processes.

Aged↗
PubMed1989

Probability and sampling.

The concept of probability is introduced, and the role of probability distributions in statistical theory is discussed, with particular reference to the Normal distribution and its characteristics. Sampling and sampling variation are described, together with sampling error, the standard error of the mean, and confidence intervals for determining the likely magnitude of a population mean.

Child↗
PubMed1989

Significance tests.

Simple methods of determining whether the difference between a sample mean and a given standard value is likely to be due only to sampling error, or to be real and/or of practical importance, are described. The use of the null hypothesis and of standard normal deviates is discussed, and examples are provided to illustrate the points made.

Dental Restoration, Permanent↗
PubMed2000

Inheritance of human longevity in Iceland.

The idea that human longevity is influenced by genetic factors has recently received strong support from work on other species. On the basis of partial population studies and selected kinships, significant correlations between the ages of parents and offspring have been reported, and some but not all twin studies have confirmed that human longevity is moderately inherited. However, studies based upon a relatively small proportion of a population are susceptible to sampling error and selection bias. Here we report the use of a comprehensive population-based computerised genealogy database to examine multigenerational relationships among those who live to the 95th percentile in Iceland. We have developed a clustering tool which can generate large extended pedigrees connecting individuals from any list using the genealogy database. First degree relatives of those living to the 95th percentile are almost twice as likely to live to the 95th percentile compared with controls. Furthermore, we have developed an algorithm which we have named the Minimum Founder Test (MFT) to examine the degree of relatedness of any population-based list of individuals to estimate whether a trait has a familial component. The data indicate that there is a significant genetic component to longevity. In addition, age-specific death rates are significantly lower in the offspring of long-lived parents compared with controls, especially after age 70.

Aged↗
PubMed2004

The influence of floral display size on selfing rates in Mimulus ringens.

Pollinators often visit several flowers in sequence on plants with large floral displays. This foraging pattern is expected to influence the rate of self-fertilization in self-compatible taxa. To quantify the effects of daily floral display on pollinator movements and selfing, we experimentally manipulated flower number in four replicate (cloned) arrays of Mimulus ringens (Scrophulariaceae), each consisting of genets with unique combinations of homozygous marker genotypes. Four display classes (two, four, eight and 16 flowers) were present in each array. Pollinator visitation rate per flower and seed set per fruit were unaffected by display. However, flower number strongly influenced the frequency of within-plant pollinator movements, which increased from 13.8% of probes on two-flower displays to 77.6% of probes on 16-flower displays. The proportion of within-plant movements was significantly correlated with selfing (r = 0.993). The increase from 22.9% selfing on two-flower displays to 37.3% selfing on 16-flower displays reflects changes in the extent of geitonogamous self-pollination. We estimate that approximately half of all selfing on 16-flower displays resulted from geitonogamy. Selfing also varied dramatically among fruits within display classes. Nested ANOVA indicates that differences among flowers on two-flower ramets accounted for 45.4% of the variation in selfing, differences among genets accounted for 16.1% of the variation, and statistical and sampling error accounted for 38.5% of the variation. Differences among flowers within ramets may reflect the order of sequential floral probes on a display.

Crosses, Genetic↗
PubMedDate not supplied

Optical coherence tomography: an emerging technology for biomedical imaging and optical biopsy.

Optical coherence tomography (OCT) is an emerging technology for performing high-resolution cross-sectional imaging. OCT is analogous to ultrasound imaging, except that it uses light instead of sound. OCT can provide cross-sectional images of tissue structure on the micron scale in situ and in real time. Using OCT in combination with catheters and endoscopes enables high-resolution intraluminal imaging of organ systems. OCT can function as a type of optical biopsy and is a powerful imaging technology for medical diagnostics because unlike conventional histopathology which requires removal of a tissue specimen and processing for microscopic examination, OCT can provide images of tissue in situ and in real time. OCT can be used where standard excisional biopsy is hazardous or impossible, to reduce sampling errors associated with excisional biopsy, and to guide interventional procedures. In this paper, we review OCT technology and describe its potential biomedical and clinical applications.

Animals↗
PubMedDate not supplied

Characterizing tumors using metabolic imaging: PET imaging of cellular proliferation and steroid receptors.

Treatment decisions in oncology are increasingly guided by information on the biologic characteristics of tumors. Currently, patient-specific information on tumor biology is obtained from the analysis of biopsy material. Positron emission tomography (PET) provides quantitative estimates of regional biochemistry and receptor status and can overcome the sampling error and difficulty in performing serial studies inherent with biopsy. Imaging using the glucose metabolism tracer, 2 -deoxy-2- fluoro-D-glucose (FDG), has demonstrated PET's ability to guide therapy in clinical oncology. In this review, we highlight PET approaches to imaging two other aspects of tumor biology: cellular proliferation and tumor steroid receptors. We review the biochemical and biologic processes underlying the imaging, positron-emitting radiopharmaceuticals that have been developed, quantitative image-analysis considerations, and clinical studies to date. This provides a basis for evaluating future developments in these promising applications of PET metabolic imaging.

Cell Division↗
PubMed2000

Lateral biopsies added to the traditional sextant prostate biopsy pattern increases the detection rate of prostate cancer.

Urologists routinely use the systematic sextant needle biopsy technique to detect prostate cancer. However, recent evidence suggests that this technique has a significant sampling error and data based upon whole-mounted step-sectioned radical prostatectomy specimens using a three-dimensional computer-assisted prostate biopsy simulator suggests that an increased detection rate is possible using laterally placed biopsies. The simulated 10-core biopsy pattern (traditional sextant biopsy cores and four laterally placed biopsies in the right and left apex and mid portion of the prostate gland) was shown to be superior to the traditional sextant biopsy. The objective of this pilot study was to confirm the higher prostate cancer detection rate obtained using the 10-core biopsy pattern in patients. We reviewed data on 35 consecutive patients with a pathologic diagnosis of prostate cancer biopsied by a single urologist using the 10-core biopsy pattern. The frequency of positive biopsy was determined for each core. Additionally, the sextant and 10-core prostate biopsy patterns were compared with respect to prostate cancer detection rate. Of the 35 patients diagnosed with prostate cancer, 54.3%(19/35) were diagnosed by the sextant biopsy only. The 10-core pattern resulted in an additional 45.7%(16/35) of patients being diagnosed solely with the laterally placed biopsies. The laterally placed biopsies had the highest frequency of positive biopsies when compared to the sextant cores. In conclusion, biopsy protocols that use laterally placed biopsies based upon a five region anatomical model are superior to the routinely used sextant prostate biopsy pattern. Prostate Cancer and Prostatic Diseases (2000) 3, 43-46

Journal Article↗
PubMed1991

Measurement of tumour protein synthesis in vivo in human colorectal and breast cancer and its variability in separate biopsies from the same tumour.

1. A method is described for measuring the rates of protein synthesis in vivo in human colorectal and breast tumours by the intravenous injection of L-[1-13C]leucine as a 'flooding dose'. 2. The incorporation of isotope into colorectal tumour protein was measured in six patients, whose tumours were biopsied after the injection. Fractional rates of protein synthesis were calculated from the enrichment of leucine in protein and the average free leucine enrichment in plasma. The range of rates obtained was 17.2-33.9%/day, with a mean rate (+/- SEM) of 22.5 +/- 2.6%/day. 3. Tumour protein synthesis rates were also measured in 15 patients with breast cancer. The range of rates obtained was 5.3-15.9%/day, with a mean rate (+/- SEM) of 10.3 +/- 0.8%/day. These rates are significantly lower than those obtained with colorectal tumours (P less than 0.001). 4. In 9 of the breast cancer patients, protein synthesis was measured in multiple random biopsies taken from the same tumour. The mean (+/- SEM) difference between the highest and lowest rates in biopsies from the same tumour was only 1.1 +/- 0.3%/day. Only 13% of the variation in protein synthesis between separate tumours could be explained by sampling error because of variation within the tumour itself, the remainder being genuine variation between individual tumours.

Adult↗
PubMed1997

H2-receptor antagonists and antacids have an aggravating effect on Helicobacter pylori gastritis in duodenal ulcer patients.

BACKGROUND: Antacids, such as aluminium-magnesium hydroxide (AIMg(OH)3), or H2-receptor antagonists, such as ranitidine, are common drugs used for treating peptic ulcer disease and acid-related symptoms. METHODS: In a prospective double-blind controlled study, 174 patients were randomized to a 4-week course of treatment with either AIMg(OH)3 (acid-binding capacity: 280 mval/day) or ranitidine 300 mg for active Helicobacter pylori-associated duodenal ulcers (as determined by histology and the urease test). Before and after treatment, two biopsy specimens each were obtained from the antrum and corpus, and the grade and activity of gastritis, as well as H. pylori density, were determined using a score ranging from 0 = none to 4 = severe. RESULTS: Pre- and post-treatment histology were available for 138 patients (AIMg(OH)3: 67, ranitidine; 71). Treatment with AIMg(OH)3 significantly increased the activity of corpus gastritis (Wilcoxon signed-rank: P = 0.0014), while ranitidine treatment significantly increased both the grade and activity of corpus gastritis (P = 0.0002 and P = 0.0001 respectively). In the antrum, both regimens provoked a significant increase in the frequency of intestinal metaplasia, but this may be a consequence of sampling error. CONCLUSIONS: Ranitidine and AIMg(OH)3 have an aggravating effect on H. pylori gastritis in duodenal ulcer patients. This should be considered a side-effect of the respective drugs and is more pronounced with ranitidine.

Aluminum Hydroxide↗
PubMed1999

Multicentre study of ultrasonographically guided axillary node biopsy in patients with breast cancer.

BACKGROUND: Axillary lymph node dissection is still performed as a staging procedure since lymph node status is the most important prognostic factor in patients with breast cancer. Sentinel node biopsy may replace routine axillary lymphadenectomy, especially in patients with small breast cancers. This study investigated whether ultrasonographically guided fine-needle aspiration cytology (FNAC) of the axillary lymph nodes in clinically node-negative patients was an accurate staging procedure to select patients for sentinel node biopsy. METHODS: One hundred and eighty-five consecutive patients were included. All had axillary ultrasonography and detected nodes were categorized according to their dimensions and echo patterns. Ultrasonographically guided FNAC was carried out if technically possible. These results were compared with the results of the sentinel node biopsy and subsequent axillary dissection. RESULTS: In 116 patients no lymph nodes were detected by ultrasonographic imaging. Of 69 patients with visible nodes, 31 had malignant cells on FNAC. There were no false-positive results. Some 87 of 185 patients had axillary metastases on definitive histological examination. Ultrasonography was sensitive in patients with extensive nodal involvement. Failure of the examination was caused by problems learning the method, difficulty in puncturing small lymph nodes and sampling error. CONCLUSION: In patients without palpable axillary nodes, a sentinel node biopsy could be avoided in 17 per cent since ultrasonography combined with FNAC had already diagnosed axillary metastases. The method is particularly valuable in larger breast cancers.

Adult↗
PubMed1997

The effects of different sampling techniques on smear quality and the diagnosis of cytological abnormalities in cervical screening.

A major cause of false-negative cervical smear is sampling error. We examined the results obtained with three different instruments in 126,608 smears from general practitioners. The spatula/brush combination yielded the highest proportion of smears showing cytological abnormalities, and the Cervex brush the lowest. Although not a randomized study, this paper highlights the shortcomings of the Cervex brush. We postulate a mechanical deficiency. Diagnostic accuracy rather than a high proportion of good quality smears should dictate the choice of instrument.

Cervix Uteri↗
PubMed2001

Fine needle aspiration cytology of primary lymphoma of the thyroid: a report of 17 cases.

Between 1980 and 1998, 4272 thyroid surgical specimens with a preoperative fine needle aspirate were sent to our Anatomical Pathology Department. Among these cases there were 17 primary thyroid lymphomas, which constituted 0.3% of all the thyroid lesions and 2.3% of the thyroid malignancies. Seven cases were diffuse large B-cell (DLBC) lymphomas and 10 were MALT lymphomas. Of the DLBC lymphomas six were correctly diagnosed by fine needle aspiration cytology (FNAC) and one was diagnosed as positive for malignancy, and among MALT lymphomas four were diagnosed as lymphoma, four as suspicious for lymphoma, and three as Hashimoto's thyroiditis (HT). Our data indicate that the diagnosis of primary thyroid lymphoma of high grade is easy, and immunocytochemistry (ICC) can confirm suspicious cases. The diagnosis of MALT lymphoma is more difficult; ICC can confirm suspicious cases, and false-negative results seem to be caused by sampling error, because HT usually coexists with MALT lymphoma.

Adult↗
PubMed2001

Fine needle aspiration cytology of thyroid nodules: how accurate is it and what are the causes of discrepant cases?

Fine-needle aspiration cytology (FNAC) is widely accepted as the most accurate, sensitive, specific and cost-effective diagnostic procedure in the assessment of thyroid nodules and helps to select people preoperatively for surgery. The purpose of this study was to evaluate the results of thyroid FNAC in our institution and to determine the reasons for discrepancies between the cytological and histological diagnosis. We evaluated the cytological and histological results of 254 FNACs obtained from 231 patients who underwent subsequent thyroid surgery. All of the material was blindly reviewed for quality control, by one experienced cytopathologist. All FNACs were carried out under ultrasound guidance. The cytological diagnosis was classified as benign, suspicious, malignant or unsatisfactory. The definitive histological study showed benign lesions in 195 of the 231 patients (84%). A benign diagnosis based on FNAC was correct in 105 of the 108 benign cases (97%). FNACs diagnosed as 'suspicious' resulted in a distribution of 49 benign (79%) and 13 malignant (21%) diagnoses. FNAC showed malignancy in 34 cases (13%) and in only one case did the final histology differ from cytology (correlation 97%). The percentage of FNACs that were inadequate for diagnosis was 20%. Review of cytological and histological slides did not lead to any change in the original diagnosis. Our study revealed a cytological-histological discrepancy (2%) in only 4 out of 231 cases over a period of 10 years, due to either a diagnostic or sampling error.

Adolescent↗