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PubMed1997

Estimating potential savings in cancer deaths by eliminating regional and social class variation in cancer survival in the Nordic countries.

STUDY OBJECTIVES: To examine equity in the health care system with regard to cancer patient care by estimating the level of systematic regional variation in cancer survival in the Nordic countries. Specifically, those cancer sites which exhibit high levels of systematic regional variation in survival and hence inequity were identified. Estimating the reduction in cancer deaths which could be achieved by eliminating this variation so that everyone receives effective care will provide a readily interpretable measure of the amount of systematic regional variation. A comprehensive analysis of regional variation in survival has not previously been conducted so appropriate statistical methodology must be developed. SETTING AND PARTICIPANTS: All those aged 0-90 years who had been diagnosed with at least one of 12 common malignant neoplasms between 1977 and 1992 in Denmark, Finland, Norway, and Sweden. DESIGN: A separate analysis was conducted for each country. Regression models for the relative survival ratio were used to estimate the relative risk of excess mortality attributable to cancer in each region after correcting for age and sex. An estimate of the amount of systematic regional variation in survival was obtained by subtracting the estimated expected random variation from the observed regional variation. An estimate was then made of the potential reduction in the number of cancer deaths for 2008-12 if regional variation in survival were eliminated so that everyone received the same level of effective care. MAIN RESULTS: Between 2008 and 2012, an estimated 2.5% of deaths from cancers in the 12 sites studied could be prevented by eliminating regional variation in survival. The percentage of potentially avoidable deaths did not depend on country or sex but it did depend on cancer site. There was no relationship between the level of regional variation in a given country and the level of survival. The cancer sites for which the greatest percentage savings could be achieved were melanoma (11%) and cervix uteri (6%). The sites for which the highest number of deaths could be prevented were prostate, colon, melanoma, and breast. CONCLUSIONS: This methodology showed a small amount of systematic regional variation in cancer survival in the Nordic countries. The cancer sites with high levels of regional variation identified are potential targets for cancer control programmes.

Adolescent↗

PubMed1999

Lumbosacral plexus in Hoxa9 knockout mice with special reference to their nerve variations identified according to whether they were interphenotypic or intergenotypic differences.

The lumbosacral plexus in specific Hox gene mutant mice originating from C57bl/60, i.e., Hoxa9 +/+, +/- and -/- genotypes (10 specimens of each), were dissected minutely and detailed examinations were made of the eight nerves in the plexus and the lowest intercostal nerve. We identified three types of nerve variation in mice with Hox mutations: interphenotypic variations, intergenotypic variations and common variations regardless of the genotype axial phenotype. The interphenotypic variations involved a caudal shift of the nerve origin in mice with the Hoxa9 -/- axial phenotype. We divided these variations into three patterns according to whether or not nerve configurations in mice with the wild and/or Hoxa9 -/- axial phenotypes were consistent, as follows: 1) the iliohypogastric and pudendal nerve morphologies of either of the phenotypes were consistent; 2) the femoral, obturator and sciatic nerve morphologies of the wild axial phenotype were consistent, but those of the -/- phenotype showed several variations and 3) both phenotypes showed several variations of the ilioinguinal and genitofemoral nerves. The intergenotypic variations, were limited to two examples: the common trunk formation of the ilioinguinal and iliohypogastric nerves in mice with the +/- and -/- genotypes, regardless of their axial phenotypes, and the territory of the ilioinguinal nerve touched the lateral margin of the thigh in the wild genotype, but extended beyond the margin onto the posterior aspect in the -/- genotype. The common variations regardless of either axial phenotype or genotype, included the lateral cutaneous nerve of the thigh which showed a limited, common variation in both of the nerve origin, ramification pattern and territory among either the three genotypes or two axial phenotypes. We consider the interphenotypic variations to be consistent with previous experimental findings showing a discrepancy between the nerve origins and their cues for nerve pathfinding. However, this developmental sequence did not seem to apply to the intergenotypic or common variations.

Animals↗

PubMed1993

Small area variation analysis. Methods for comparing several diagnosis-related groups.

In small-area variation analysis, the variation of health care utilization rates, e.g., admission rates, among small areas is calculated. Frequently, the variation of one diagnosis, diagnosis-related group (DRG), or procedure is compared with the variation of another. Unfortunately, the methods generally used to make these comparisons are not consistent. They differ on whether they 1) adjust for the prevalence of the DRGs, 2) distinguish between variation among areas and variation within areas, 3) weight all areas equally, and 4) adjust for multiple admissions per person. None has an associated confidence interval. These discrepancies occur in part because there is no statistical model of small area variation. Without such a model, it is not known how to measure variation, and thus, it is not known how to compare different DRGs. Here, the authors use data on 473 DRGs from 28 counties in Washington state to study the nature of variability. The variation was higher for the more prevalent DRGs, suggesting that adjusting for prevalence may be reasonable. The true coefficient of variation appears to be a "natural" measure of variation, but the usual small area variation statistics do not provide good estimates of the true coefficient of variation. A new estimate is proposed that can be used to compare and test the variability of several DRGs.

Analysis of Variance↗

PubMed1997

The relationship between variations in knee replacement utilization rates and the reported prevalence of arthritis in Ontario, Canada.

OBJECTIVE: To determine the relationship between regional variations in knee replacement (KR) utilization rates in Ontario, Canada, and the reported prevalence of arthritis and rheumatism as a chronic health problem. METHODS: Utilization data were acquired from the Canadian Institute for Health Information for KR procedures performed in Ontario between fiscal years 1984 and 1990. Census information was obtained from Statistics Canada. Disease prevalence data were derived from the 1990 Ontario Health Survey (OHS). Public Health Units (PHU) were used as the unit of analysis, with utilization rates defined as the number of KR performed on all PHU residents (irrespective of where these procedures were performed) divided by the population. Direct methods were used to standardize utilization for age, sex, and disease prevalence. The extremal quotient, the weighted coefficient of variation, and the systematic component of variation were used as measures of variation. The relationship between the number of KR performed in each age-sex-year strata and various demographic (age and sex), disease prevalence, and regional dummy variables was estimated using a Poisson regression model. RESULTS: Regional variation in the standardized utilization of KR surgery was wide, but declined over the study period; the extremal quotient fell from 8.0 to 3.3, the weighted coefficient of variation fell from 0.49 to 0.30, and the systematic component of variation fell from 0.20 to 0.17. Variation in the provision of KR surgery remained even after controlling for the demographic composition of the population and disease prevalence. Moreover, while demographic, regional, and temporal covariates were significant (p < 0.0001) in accounting for over 90% of the variation in utilization, disease prevalence was not significant (p > 0.05). CONCLUSION: This study merged population based reports of disease prevalence with administrative data to account for regional variations in utilization. While regional variations in KR surgery have fallen over time, variations remain even after adjusting for patient reported disease prevalence. The finding that demographic variables and the reported prevalence of disease were poorly correlated suggests that current area variation studies may not be adjusting fully for disease prevalence or severity.

Aged↗

PubMed1998

An ecological study of association between coronary heart disease mortality rates in men and the relative frequencies of common allelic variations in the gene coding for apolipoprotein E.

Three common alleles, epsilon2, epsilon3, and epsilon4, of the gene coding for apolipoprotein E (apoE) have been identified as predictors of interindividual variation in measures of lipid and lipoprotein metabolism, and ultimately risk of coronary heart disease (CHD), within many populations. Here we evaluated the utility of the geographic distribution of these alleles for prediction of interpopulation variation in average level of serum total cholesterol and other traditional risk factors, and CHD mortality rate. We employed published estimates of the relative frequencies of the three common apoE alleles, average levels of risk factors such as serum total cholesterol, systolic and diastolic blood pressure, body mass index, smoking prevalence and CHD mortality rate for nine population-based samples of middle-aged males studied by the international WHO MONICA Project. There was approximately a 10-fold difference between the highest and lowest CHD mortality rate. Of the traditional risk factors, variation in the average level of serum total cholesterol was the best predictor (approximately 33%) of the observed interpopulation variation in estimates of CHD mortality rate (Pr=0.10). Variation in the relative frequency of the epsilon4 allele predicted approximately 50% of interpopulation variation in average serum total cholesterol level (Pr=0.02) and 75% of the variation in CHD mortality rate (Pr=0.002) when information about variation in the other risk factors and the epsilon2 and epsilon3 alleles is ignored. Furthermore, variation in the relative frequency of the epsilon4 allele predicted approximately 40% of the variation in CHD mortality rate (Pr=0.02) after considering the contribution of variation in average serum total cholesterol level. Average serum total cholesterol level was estimated to increase by 0.114 mmol/l (4.405 mg/dl), and CHD mortality rate by 24.5/100000, for an increase of 0.01 in the relative frequency of the epsilon4 allele. The predictive utility of the epsilon2 and epsilon3 alleles was considerably less than that of the epsilon4 allele. For the sample of populations considered, the geographic distribution of the apoE alleles can be a statistically significant predictor of interpopulation variation in both the average serum total cholesterol level and CHD mortality rate. In particular, the epsilon4 allele may confer valuable ecological risk information.

Alleles↗

PubMed2001

Female guppies agree to differ: phenotypic and genetic variation in mate-choice behavior and the consequences for sexual selection.

Variation among females in mate choice may influence evolution by sexual selection. The genetic basis of this variation is of interest because the elaboration of mating preferences requires additive genetic variation in these traits. Here we measure the repeatability and heritability of two components of female choosiness (responsiveness and discrimination) and of female preference functions for the multiple ornaments borne by male guppies (Poecilia reticulata). We show that there is significant repeatable variation in both components of choosiness and in some preference functions but not in others. There appear to be several male ornaments that females find uniformly attractive and others for which females differ in preference. One consequence is that there is no universally attractive male phenotype. Only responsiveness shows significant additive genetic variation. Variation in responsiveness appears to mask variation in discrimination and some preference functions and may be the most biologically relevant source of phenotypic and genetic variation in mate-choice behavior. To test the potential evolutionary importance of the phenotypic variation in mate choice that we report, we estimated the opportunity for and the intensity of sexual selection under models of mate choice that excluded and that incorporated individual female variation. We then compared these estimates with estimates based on measured mating success. Incorporating individual variation in mate choice generally did not predict the outcome of sexual selection any better than models that ignored such variation.

Animals↗

PubMedDate not supplied

Variation in the diagnosis of upper respiratory tract infections and otitis media in an urgent medical care practice.

BACKGROUND: Variation among hospitalized medical conditions have been reported previously, but there is little information on variation among physicians for medical conditions that constitute a substantial part of ambulatory care. OBJECTIVE: To measure variation in the diagnosis of 2 common medical conditions, otitis media (OM) and upper respiratory tract infections (URIs) in an urgent care practice. DESIGN: Estimate the variation in the incidence of new diagnoses of OM and URIs among 19 physicians working at 2 urgent care clinics between January 1, 1995, and March 31, 1995. Patients are seen in order of arrival, and assignment to each physician is random. PARTICIPANTS AND SETTING: Two urgent care clinics staffed by the same 19 physicians. During the 3-month study period, 21,259 patients were seen at the 2 clinics; of these, 1839 (8.65%) received a diagnosis of first time OM; and 8020 (37.73%), of an URI. MAIN OUTCOME MEASURE: Incidence of new diagnoses of OM and URI estimated as a proportion of all diagnoses for each individual physician. RESULTS: There was substantial variation between physicians in the diagnosis of OM, ranging from a low of 4.2% to a high of 21.8%. There was less variation in the diagnosis of URI (31.7%-48.4%). Some physicians with a low incidence of OM or URI diagnoses had increased the proportion of diagnoses in the other diagnostic category. For OM the variation was greatest for children younger than age 5 years, but substantial variation was also found in adults. For URIs the variation was more uniform across all age groups. The variation was not explained by type of specialty training or years in medical practice. CONCLUSIONS: There is substantial variation between physicians in their diagnosis of OM and URI in an urgent care setting. This variation has implications for cost of diagnosing and treating these conditions, the training of physicians, and our understanding of the treatment of OM.

Adolescent↗

PubMed2000

Craniofacial variation in Homo habilis: an analysis of the evidence for multiple species.

The question of heterogeneity in the Homo habilis sample continues to be controversial. Various lines of evidence have been used to reject the null hypothesis of intraspecific variation. This evidence derives from analyses of endocranial volume variation, probability estimates of sexual dimorphism, facial variation, cranial angles, CV analysis of craniofacial variation, the multivariate pattern of sexual dimorphism, the pattern of variability (CV) profiles, distance data using exact randomization methods, and various kinds of quantitative ordinations of fossils. Although consensus is lacking as to how the H. habilis sample is to be split, there is a growing perception that the degree of variation among the fossils is too great and the pattern of variation is too different to be explained by intraspecific variation. This has resulted in the recognition of new species such as "Homo rudolfensis." The present study critically examines the evidence commonly cited as the basis for recognizing multiple species in the extended H. habilis hypodigm. Reanalysis and reinterpretation of these data indicates that: (1) the degree of variation in the H. habilis sample is typical of modern hominoids, and (2) the pattern of variation among specimens of the H. habilis sample is consistent with intraspecific variation. Thus, at present, there is no sound basis to reject the null hypothesis of intraspecific variation as an adequate explanation of the morphological variation seen among specimens of the extended H. habilis sample. If multiple species are indeed represented, then their presence has not yet been satisfactorily demonstrated.

Animals↗

PubMed1999

The development of within-song type variation in song sparrows.

We investigated the development of within-song type variation in song sparrows, Melospiza melodia, with two experiments designed to determine how exposure to within-type variation influences the song-learning process and whether within-type variation itself is a learned trait. In the first experiment, we compared learning between two groups of males, one group tutored exclusively with song models presented with no variation, and the other group tutored exclusively with song models presented with a range of within-type variation that is normally produced by birds in the field. The two groups in this experiment did not differ significantly in any measure of how well they learned, suggesting that exposure to within-type variation has no measurable influence on the learning process overall. Nor did the groups differ in the expression of within-song type variation in their own adult songs, demonstrating that within-type variation is not a learned feature of song sparrow song. In the second experiment, we tutored a single group of birds with both invariant and variable models, allowing us to ask how within-type variability affects learning preferences. Young birds preferentially copied song type models presented with variation significantly more than invariant models. Taken together, these experiments provide insight into the evolution of within-song type variation in song sparrows, although the functional significance of this level of variation and learning preferences based on variation remain enigmatic. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2006

Single-nucleotide variations in the genes encoding the mitochondrial Hsp60/Hsp10 chaperone system and their disease-causing potential.

Molecular chaperones assist protein folding, and variations in their encoding genes may be disease-causing in themselves or influence the phenotypic expression of disease-associated or susceptibility-conferring variations in many different genes. We have screened three candidate patient groups for variations in the HSPD1 and HSPE1 genes encoding the mitochondrial Hsp60/Hsp10 chaperone complex: two patients with multiple mitochondrial enzyme deficiency, 61 sudden infant death syndrome cases (MIM: #272120), and 60 patients presenting with ethylmalonic aciduria carrying non-synonymous susceptibility variations in the ACADS gene (MIM: *606885 and #201470). Besides previously reported variations we detected six novel variations: two in the bidirectional promoter region, and one synonymous and three non-synonymous variations in the HSPD1 coding region. One of the non-synonymous variations was polymorphic in patient and control samples, and the rare variations were each only found in single patients and absent in 100 control chromosomes. Functional investigation of the effects of the variations in the promoter region and the non-synonymous variations in the coding region indicated that none of them had a significant impact. Taken together, our data argue against the notion that the chaperonin genes play a major role in the investigated diseases. However, the described variations may represent genetic modifiers with subtle effects.

Butyryl-CoA Dehydrogenase↗

PubMed2003

Across-site variation in detection thresholds and maximum comfortable loudness levels for cochlear implants.

In cochlear implants, variation across stimulation sites in psychophysical detection thresholds (T levels) and maximum comfortable loudness levels (C levels) can be large when narrow-bipolar (BP) stimulation is used. This across-site variation is typically smaller when monopolar (MP) stimulation is used. At least two models can account for across-site variation and the effects of electrode configuration on the magnitude of the variation. According to one model, across-site variation reflects site-to-site differences in the distances between the stimulating electrodes and the sites of action-potential initiation. Under this model, the lower across-site variation with MP stimulation is due to shallower current versus distance gradients. An alternative model assumes that T and C levels depend on integration of activity across the whole population of neurons and that MP stimulation activates neurons over a larger spatial extent than does BP stimulation. If T and C levels are determined by integration of activity across large overlapping populations of neurons, then their values at adjacent sites should be more similar than if these levels result from integration across smaller, more independent populations. We tested the models by examining the effects on across-site variation of three variables believed to affect the spatial extent of activation: electrode configuration, stimulus level within the dynamic range, and electrode-array design. T levels and C levels were measured in 13 subjects with Nucleus CI24M (straight array) and 9 subjects with Nucleus CI24R(CS) (Contour) cochlear implants using bipolar (BP) and monopolar (MP) electrode configurations. Site-to-site variation in T and C levels for BP stimulation was 2.1-3.3 times larger than that for MP stimulation. Contrary to the across-neuron integration hypothesis, no significant differences were found between across-site variation for T levels and that for C levels for the BP configuration. There was considerable overlap in site-to-site variation values for the two types of implants but mean site-to-site variation in C levels for CI24M implants was significantly lower than that for CI24R(CS) implants. Control studies suggested that these results were not an artifact of the scale, and not due to differences in inherent variability of the psychophysical measures, or to the method of quantifying across-site variation.

Adult↗

PubMed1993

Heart rate variation during fetal behavioural states 1 and 2.

Fetal heart rate (FHR) variation was numerically assessed in relation to behavioural states in 34 normal near term fetuses, in order to study the normal ranges of FHR variation during state 1F and 2F and to determine possible factors influencing variation in these states. In all individuals 2-h recordings were made of fetal heart rate, and body and eye movements. FHR variation was quantified using the Sonicaid System 8000. During both 1F and 2F there was a large range in variation, with a wide overlap in variation between both states (mean 1-min range in pulse intervals 16-53 ms and 36-97 ms, respectively). In all fetuses variation was higher during 2F than during 1F. The large ranges in variation were mainly caused by differences in basal heart rate and the correlation coefficients between rate (beats/min) and variation were -0.68 and -0.49 for 1F and 2F, respectively. Other reasons for a relatively high FHR variation during 1F included 'pseudo' sinusoidal patterns related to fetal sucking or mouth movements and relatively flat periods sporadically interrupted by an acceleration. With the System 8000, periods of low and high variation are identified using fixed criteria. Because of the large overlap in variation between both states, these episodes poorly correlated with the underlying behavioural states. Objective identification of the heart rate patterns during states 1F and 2F requires incorporation of heart rate itself in the analysis. As yet, 'global' visual identification of heart rate patterns is superior to computer analysis in identifying the underlying fetal behavioural states.

Behavior↗

PubMed2002

Avian egg size: variation within species and inflexibility within individuals.

Egg size is a widely-studied trait and yet the causes and consequences of variation in this trait remain poorly understood. Egg size varies greatly within many avian species, with the largest egg in a population generally being at least 50% bigger, and sometimes twice as large, as the smallest. Generally, approximately 70% of the variation in egg mass is due to variation between rather than within clutches, although there are some cases of extreme intra-clutch egg-size variation. Despite the large amount of variation in egg size between females, this trait is highly consistent within individuals between breeding attempts; the repeatability of egg size is generally above 0.6 and tends to be higher than that of clutch size or laying date. Heritability estimates also tend to be much higher for egg size (> 0.5) than for clutch size or laying date (< 0.5). As expected, given the high repeatability and heritability of egg size, supplemental food had no statistically significant effect on this trait in 18 out of 28 (64%) studies. Where dietary supplements do increase egg size, the effect is never more than 13% of the control values and is generally much less. Similarly, ambient temperature during egg formation generally explains less than 15% of the variation in egg size. In short, egg size appears to be a characteristic of individual females, and yet the traits of a female that determine egg size are not clear. Although egg size often increases with female age (17 out of 37 studies), the change in egg size is generally less than 10%. Female mass and size rarely explain more than 20% of the variation in egg size within species. A female's egg size is not consistently related to other aspects of reproductive performance such as clutch size, laying date, or the pair's ability to rear young. Physiological characteristics of the female (e.g. endogenous protein stores, oviduct mass, rate of protein uptake by ovarian follicles) show more promise as potential determinants of egg size. With regards to the consequences of egg-size variation for offspring fitness, egg size is often correlated with offspring mass and size within the first week after hatching, but the evidence for more long-lasting effects on chick growth and survival is equivocal. In other oviparous vertebrates, the magnitude of egg-size variation within populations is often as great or greater than that observed within avian populations. Although there are much fewer estimates of the repeatability of egg size in other taxa, the available evidence suggests that egg size may be more flexible within individuals. Furthermore, in non-avian species (particularly fish and turtles), it is more common for female mass or size to explain a substantial proportion of the variation in egg size. Further research into the physiological basis of egg-size variation is needed to shed light on both the proximate and ultimate causes of intraspecific variation in this trait in birds.

Age Factors↗

PubMed2006

Variation in chemotherapy utilization in ovarian cancer: the relative contribution of geography.

OBJECTIVE: This study investigates geographic variation in chemotherapy utilization for ovarian cancer in both absolute and relative terms and examines area characteristics associated with this variation. DATA SOURCES: Surveillance, Epidemiology, and End Results (SEER) Medicare data from 1990 to 2001 for Medicare patients over 65 with a diagnosis of ovarian cancer between 1990 and 1999. Chemotherapy within a year of diagnosis was identified by Medicare billing codes. The hospital referral region (HRR) represents the geographic unit of analysis. STUDY DESIGN: A logit model predicting the probability of receiving chemotherapy by each of the 39 HRRs. Control variables included medical characteristics (patient age, stage, year of diagnosis, and comorbidities) and socioeconomic characteristics (race, income, and education). The variation among HRRs was tested by the chi2 statistic, and the relative contribution was measured by the omega statistic. HHR market characteristic are then used to explain HRR-level variation. PRINCIPAL FINDINGS: The average chemotherapy rate was 56.6 percent, with a range by HRR from 33 percent to 67 percent. There were large and significant differences in chemotherapy use between HRRs, reflected by a chi2 for HRR of 146 (df = 38, p < .001). HRR-level variation in chemotherapy use can be partially explained by higher chemotherapy rates in HRRs with a higher percentage of hospitals with oncology services. However, an omega analysis indicates that, by about 15 to one, the variation between patients in use of chemotherapy reflects variations in patient characteristics rather than unexplained variation among HRRs. CONCLUSIONS: While absolute levels of chemotherapy variation between geographic areas are large and statistically significant, this analysis suggests that the role of geography in determining who gets chemotherapy is small relative to individual medical characteristics. Nevertheless, while variation by medical characteristics can be medically justified, the same cannot be said for geographic variation. Our finding that density of oncology hospitals predicts chemotherapy use suggests that provider supply is positively correlated with geographic variation.

Aged↗

PubMed1992

Clinical pathology: preanalytical variation in preclinical safety assessment studies--effect on predictive value of analyte tests.

Significant differences in concentrations of analytes in samples may be introduced before samples enter analyzers. These differences are known as preanalytical variation and are part of the overall variation in analytical data. Preanalytical variation is caused by factors that operate during animal preparation prior to sampling, sample collection, sample processing, and sample storage prior to measurement. Preanalytical variation is important because it detracts from the predictive value of analyte measurements. Preanalytical variation may permanently damage data. Because its effects are difficult to quantitate it should be minimized in safety assessment studies. Sources of preanalytical variation are actions performed on animals prior to sample collection and actions performed on the specimen prior to analysis. Preanalytical variation produces a range of artefacts in experimental data. Consequences of preanalytical variation are loss of confidence in the data, obfuscation of real test article effects, false effects, and possibly the expense of repeating a study. To limit preanalytical variation, its sources must be identified, the effects documented, and measures devised to eliminate its sources. Predictive value (likelihood of actual disease) of appropriate clinical pathology tests in toxicology is inversely dependent on preanalytical variation: uncontrolled variation produces data with low predictive values, and controlled variation produces data with high predictive values.

Animals↗

PubMed2005

Relation between respiratory variations in pulse oximetry plethysmographic waveform amplitude and arterial pulse pressure in ventilated patients.

INTRODUCTION: Respiratory variation in arterial pulse pressure is a reliable predictor of fluid responsiveness in mechanically ventilated patients with circulatory failure. The main limitation of this method is that it requires an invasive arterial catheter. Both arterial and pulse oximetry plethysmographic waveforms depend on stroke volume. We conducted a prospective study to evaluate the relationship between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic (POP) waveform amplitude. METHOD: This prospective clinical investigation was conducted in 22 mechanically ventilated patients. Respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude were recorded simultaneously in a beat-to-beat evaluation, and were compared using a Spearman correlation test and a Bland-Altman analysis. RESULTS: There was a strong correlation (r2 = 0.83; P < 0.001) and a good agreement (bias = 0.8 +/- 3.5%) between respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude. A respiratory variation in POP waveform amplitude value above 15% allowed discrimination between patients with respiratory variation in arterial pulse pressure above 13% and those with variation of 13% or less (positive predictive value 100%). CONCLUSION: Respiratory variation in arterial pulse pressure above 13% can be accurately predicted by a respiratory variation in POP waveform amplitude above 15%. This index has potential applications in patients who are not instrumented with an intra-arterial catheter.

Adult↗

PubMed1999

Geographic variations in the rates of operative procedures involving the shoulder, including total shoulder replacement, humeral head replacement, and rotator cuff repair.

BACKGROUND: Although geographic variations in the rates of orthopaedic procedures have been well documented, considerable controversy remains regarding the factors that drive these variations, particularly the role of the availability of orthopaedic surgeons. Moreover, little attention has been specifically focused on variations in the rates of commonly performed shoulder procedures. METHODS: The current study documents state-to-state variations in the rates of total shoulder replacement, humeral head replacement, and rotator cuff repair and examines factors that might account for these variations. The regional incidences of these three procedures were analyzed with use of the Health Care Financing Administration Medicare database (MEDPAR, 1992). The rates were age-adjusted, and variations were measured with use of high:low ratios, variation coefficients, and systematic components of variation. Potential causes of variation were analyzed with use of Spearman and partial correlations as well as with Poisson regression. RESULTS: Rates for the three procedures that were studied varied from one state to another by as much as tenfold. Humeral head replacement had the lowest rate of variation according to all three measures. All three procedures were performed less often in states that were more densely populated. With the numbers available for study, no consistent, significant relationship was found between the density of orthopaedists and shoulder surgeons and the rates of any procedure. CONCLUSIONS: The striking variations that were noted for these commonly performed procedures showed that there is a clear need for well designed clinical research to further define the factors that account for the variations and to examine the effectiveness and appropriate indications for the procedures.

Aged↗

PubMed1976

[Effects of repeated in vitro bud formation on somatic variation ability on a chlorophyll mutant of Nicotiana tabacum var. Samsun].

A homozygous tl/tl chlorophyll mutant of Nicotiana tabacum var. Samsun shows spontaneous somatic variations on its leaves. These variations are either single (dark or light) or twinned (dark and light). In vitro culture of variation-free leaf fragments, on a particular medium, directly yields neoformed buds. These buds are placed on a medium for root formation, so that neoformed plants are obtained from which a new cycle of bud neoformation can be started. In this way, one obtains several sets of plants of the same somatic origin but which differ from each other by one or more neoformation cycles. At each cycle, the somatic variation ability is characterized on the basis of four criteria: (1) numbers and proportions of dark, light and twinned variations, (2) distribution of dark variations according to their sizes, (3) distribution of variations according to the foliar level, and (4) sexual transmission of each character. As early as at the second neoformation cycle, one observes a significant increase of variability among the numbers of variations and shifts in size distributions. The increase of variability is more striking after the third cycle; particularly, plants obtained in this manner have acquired, on the average, the ability to vary earlier in the development of the foliar initium. This property is expressed through the enlargement of the mean size of the variations. In each case, the observed variability is somatically maintained through cuttings. This, together with the fact that the observed shifts in frequency distributions as well as the changes in numbers of variations are sexually transmitted after the third neoformation cycle, definitely means that genetic changes have occurred. Consequently, it seems that from one neoformation cycle to another, in vitro culture of leaf fragments has cumulative effects which, beyond a particular threshold, are sexually transmitted. The only character, among four, not to be affected by in vitro culture is the distribution of somatic variations according to the foliar level. Thus, it seems that this character is strictly controlled by changes in physiological conditions which occur during the plant growth; in particular, the transition of the shoot apex from vegetative to flowering state. The effects of in vitro culture on the ability to somatically vary are discussed on the basis of four hypotheses: (1) modification in number of chromosomes (polyploidy, aneuploidy); (2) modification in chromosome structure (translocation); (3) selection of a particular kind of cells and (4) cumulative alteration of genetic information either by mutation or by disturbance in cell regulation process.

Chlorophyll↗