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At least 1,693 records · Page 94Linked to original sources
PubMed2005

Interocular axial length difference in eyes with pediatric cataracts.

PURPOSE: We sought to report interocular axial length difference (IALD) between the operated eye and fellow eye at the time of pediatric cataract surgery. METHODS: A retrospective analysis of 171 cataractous (operated) eyes (mean patient age at surgery, 56.9 months; range, 0.2-230.0) was undertaken. Descriptive statistics, analysis of covariance, and regression analysis were used in statistical analysis. RESULTS: The mean IALD was 0.05 +/- 1.15 mm. If absolute values were used, mean IALD was 0.76 +/- 0.86. Nearly half of the subjects (48.0%) showed an IALD of >/=0.5 mm. Forty-one patients (24.0%) had operated (cataractous) eyes that were >/=0.5 mm shorter than the fellow eye, and 41 patients (24.0%) had operated eyes that were >/=0.5 mm longer than the fellow eye. The mean IALD in unilateral and bilateral cases was 0.10 +/- 1.33 and -0.03 +/- 0.76, respectively (P = 0.4). If absolute values were used, it was 0.98 +/- 0.90 and 0.40 +/- 0.65 in unilateral and bilateral cases, respectively (P < 0.001). IALD was more predictable in unilateral than in bilateral cases (P < 0.001). In unilateral cases, age at surgery (P = 0.04) and AL of the operated eye (P < 0.001) correlated with IALD. IALD did not correlate with gender, ethnicity, or type of cataract in either unilateral or bilateral cases. CONCLUSIONS: An IALD of >/=0.5 mm occurred in 48.0% of patients with pediatric cataracts and occurred more often with unilateral cataractous patients than with bilateral cases. In patients with unilateral cataract, age at surgery and AL of the operated eye could help predict the IALD.

Cataract↗
PubMedDate not supplied

A hydrologic network supporting spatially referenced regression modeling in the Chesapeake Bay Watershed.

The U.S. Geological Survey has developed a methodology for statistically relating nutrient sources and land-surface characteristics to nutrient loads of streams. The methodology is referred to as SPAtially Referenced Regressions On Watershed attributes (SPARROW), and relates measured stream nutrient loads to nutrient sources using nonlinear statistical regression models. A spatially detailed digital hydrologic network of stream reaches, stream-reach characteristics such as mean streamflow, water velocity, reach length, and travel time, and their associated watersheds supports the regression models. This network serves as the primary framework for spatially referencing potential nutrient source information such as atmospheric deposition, septic systems, point-sources, land use, land cover, and agricultural sources and land-surface characteristics such as land use, land cover, average-annual precipitation and temperature, slope, and soil permeability. In the Chesapeake Bay watershed that covers parts of Delaware, Maryland, Pennsylvania, New York, Virginia, West Virginia, and Washington D.C., SPARROW was used to generate models estimating loads of total nitrogen and total phosphorus representing 1987 and 1992 land-surface conditions. The 1987 models used a hydrologic network derived from an enhanced version of the U.S. Environmental Protection Agency's digital River Reach File, and course resolution Digital Elevation Models (DEMs). A new hydrologic network was created to support the 1992 models by generating stream reaches representing surface-water pathways defined by flow direction and flow accumulation algorithms from higher resolution DEMs. On a reach-by-reach basis, stream reach characteristics essential to the modeling were transferred to the newly generated pathways or reaches from the enhanced River Reach File used to support the 1987 models. To complete the new network, watersheds for each reach were generated using the direction of surface-water flow derived from the DEMs. This network improves upon existing digital stream data by increasing the level of spatial detail and providing consistency between the reach locations and topography. The hydrologic network also aids in illustrating the spatial patterns of predicted nutrient loads and sources contributed locally to each stream, and the percentages of nutrient load that reach Chesapeake Bay.

Delaware↗
PubMed2000

Angiogenesis in early-invasive and low-malignant-potential epithelial ovarian carcinoma.

OBJECTIVE: To evaluate angiogenesis in ovaries of women with stage I invasive and low-malignant-potential epithelial ovarian carcinoma. METHODS: Ovarian specimens of 49 consecutive women with primary stage I invasive (n = 15) or stage I low-malignant-potential epithelial ovarian carcinoma (n = 34) were stained immunohistochemically for factor VIII-related antigen. Microvessel counts were tested for correlation with patient age, race, parity, previous oral contraceptive use, histologic type, tumor grade, tumor size, ascites, tumor excrescences, and disease-free and overall survival. Statistical analysis included multiple linear regression, Student t tests, factorial analysis of variance, and Cox proportional hazards regression, with P <.05 considered statistically significant. RESULTS: Microvessel counts of ovarian specimens of women with stage I invasive epithelial ovarian carcinoma (median 30, range 17-73) were significantly higher than those of women with stage I low-malignant-potential epithelial ovarian carcinoma (median 10, range 5-23), (P <.001). Among women with low-malignant-potential disease, microvessel counts did not differ significantly between serous and mucinous carcinomas (median 10, range 5-23 versus median 11, range 5-20, respectively, P =.78). There was no correlation between microvessel counts and age, tumor grade, tumor size, ascites, or tumor excrescences. CONCLUSION: Angiogenesis as assessed by microvessel counts is more intense in stage I invasive ovarian epithelial carcinoma compared with stage I low-malignant-potential carcinoma, and might assist in differentiating between these histopathologic entities.

Adolescent↗
PubMed2003

Born out of wedlock and never married--it breaks a man's heart.

This study examines whether men who were born outside marriage in early twentieth century Sweden run a higher risk of dying from ischaemic heart disease (IHD) in middle and old age compared to men who were born inside marriage. Analyses are based on the male half of the Uppsala Birth Cohort Study, Sweden, consisting of all 7411 boys who were born alive at the Uppsala Academic Hospital during the period 1915-1929. The statistical method used is Cox regression. The results demonstrated a statistically significant excess mortality among men born outside marriage, which could not be explained by either social class of origin or birth weight for gestational age. Instead, this elevated mortality was largely explained by the more than doubled mortality risk among those men born outside wedlock who never married in relation to the corresponding group of men born to married parents. Even when three indicators of adult socio-economic status were adjusted for, men who never married and were born outside marriage still ran a 93 per cent higher risk of dying from IHD than men who never married but were born inside marriage. This intervening effect of adult marital status was restricted to the category of never married men. Thus, although divorcees demonstrated an even higher mortality risk in relation to the married than did those who never married, this was equally true for men born inside and men born outside marriage. In the concluding section of the paper I argue that these findings should be understood in terms of the childhood social stigma that the illegitimate children experienced. This stigma may have resulted in an increased susceptibility, which in combination with the "failure" in adulthood to comply with the established norms of society regarding matrimony led to higher levels of IHD mortality in middle and old age.

Aged↗
PubMed2003

Emergence of sentinel node biopsy in breast cancer as standard-of-care in academic comprehensive cancer centers.

BACKGROUND: Ongoing clinical trials are addressing the accuracy and safety of sentinel node biopsy (SNB) in the treatment of breast cancer; however, SNB is already increasingly being used in clinical practice. This study examined the extent and time trends of the use of SNB in stage I and II breast cancer patients. METHODS: Clinical data were collected from stage I and II (tumor size < or =5.0 cm) breast cancer patients (n = 3003) who were treated at five comprehensive cancer centers between July 1, 1997, and December 31, 2000. Axillary surgery was classified as SNB alone, SNB + axillary node dissection (AND), AND alone, or none. Patterns of use of axillary surgery were summarized as the percentage of patients receiving each surgery type. The statistical significance of time trends for the use of SNB alone was analyzed by logistic regression models. All statistical tests were two-sided. RESULTS: Overall, SNB alone was used in 13% of patients, SNB + AND in 22%, AND alone in 59%, and no axillary surgery in 6%. Use of SNB alone was statistically significantly associated with breast-conserving surgery of both smaller (< or =2 cm) and larger tumors (2-5 cm) (P<.001 for both associations). For stage I cancer patients treated with breast-conserving surgery (n = 1763), use of SNB increased statistically significantly over the study period, from 8% in 1997 to 9%, 14%, 15%, 22%, 42%, and 58% for the next six consecutive 6-month time intervals, respectively. After controlling for center, age, and comorbidity, the odds ratio for the use of SNB alone was 2.30 (95% confidence interval = 1.88 to 2.82) for each 6-month interval (P<.001). CONCLUSIONS: Widespread use of SNB outside the clinical trial setting suggests that oncologists at cancer centers in our study have accepted SNB as standard-of-care for the treatment of breast cancer. This acceptance, if it occurs in other cancer centers and community practice, may affect accrual and generalizability of ongoing clinical trials of SNB.

Academic Medical Centers↗
PubMed2005

Monitoring device safety in interventional cardiology.

OBJECTIVE: A variety of postmarketing surveillance strategies to monitor the safety of medical devices have been supported by the U.S. Food and Drug Administration, but there are few systems to automate surveillance. Our objective was to develop a system to perform real-time monitoring of safety data using a variety of process control techniques. DESIGN: The Web-based Data Extraction and Longitudinal Time Analysis (DELTA) system imports clinical data in real-time from an electronic database and generates alerts for potentially unsafe devices or procedures. The statistical techniques used are statistical process control (SPC), logistic regression (LR), and Bayesian updating statistics (BUS). MEASUREMENTS: We selected in-patient mortality following implantation of the Cypher drug-eluting coronary stent to evaluate our system. Data from the University of Michigan Consortium Bare-Metal Stent Study was used to calculate the event rate alerting boundaries. Data analysis was performed on local catheterization data from Brigham and Women's Hospital from July 1, 2003, shortly after the Cypher release, to December 31, 2004, including 2,270 cases with 27 observed deaths. RESULTS: The single-stratum SPC had alerts in months 4 and 10. The multistrata SPC had alerts in months 5, 10, and 18 in the moderate-risk stratum, and months 1, 4, 7, and 10 in the high-risk stratum. The only cumulative alerts were in the first month for the high-risk stratum of the multistrata SPC. The LR method showed no monthly or cumulative alerts. The BUS method showed an alert in the first month for the high-risk stratum. CONCLUSION: The system performed adequately within the Brigham and Women's Hospital Intranet environment based on the design goals. All three cumulative methods agreed that the overall observed event rates were not significantly higher for the new medical device than for a closely related medical device and were consistent with the observation that the initial concerns about this device dissipated as more data accumulated.

Bayes Theorem↗
PubMed2002

Impact of estradiol supplementation on dual peptidyl drive of GH secretion in postmenopausal women.

As an indirect probe of estrogen-regulated hypothalamic somatostatin restraint, the present study monitors the ability of short-term oral E2 supplementation to modulate GH secretion during combined continuous stimulation by recombinant human GHRH [GHRH-(1-44)-amide] and the potent and selective synthetic GH-releasing peptide, GHRP-2. According to a simplified tripeptidyl model of GH neuroregulation, the effects of estrogen in this dual secretagogue paradigm should mirror alterations in endogenous somatostatinergic signaling. To this end, seven healthy postmenopausal women underwent frequent (10-min) blood sampling for 24 h during simultaneous i.v. infusion of GHRH and GHRP-2 each at a rate of 1 microg/kg x h on d 10 of randomly ordered placebo or 17beta-estradiol (E2) (1 mg orally twice daily) replacement. Serum GH concentrations (n = 280/subject) were assayed by chemiluminescence. The resultant GH time series was evaluated by deconvolution analysis, the approximate entropy statistic, and cosine regression to quantitate pulsatile, entropic (feedback-sensitive), and 24-h rhythmic GH release, respectively. Statistical comparisons revealed that E2 repletion increased the mean (+/- SEM) serum E2 concentration to 222 +/- 26 pg/ml from 16 +/- 1.7 pg/ml during placebo (P < 0.001) and suppressed the serum LH by 48% (P = 0.0033), serum FSH by 64% (P < 0.001), and serum IGF-I by 44% (P = 0.021). Double peptidyl secretagogue stimulation elevated mean 24-h serum GH concentrations to 8.1 +/- 1.0 microg/liter (placebo) and 7.7 +/- 0.89 microg/liter (E2; P = NS) and evoked prominently pulsatile patterns of GH secretion. No primary measure of pulsatile or basal GH release was altered by the disparate sex steroid milieu, i.e. GH secretory burst amplitudes of 0.62 +/- 0.93 (placebo) and 0.72 +/- 0.16 (E2) microg/liter x min, GH pulse frequencies of 27 +/- 1.8 (placebo) and 23 +/- 1.9 (E2) events/24 h, GH half-lives of 12 +/- 0.74 (placebo) and 15 +/- 4.5 (E2) min, and basal (nonpulsatile) GH secretion 70 +/- 22 (placebo) and 57 +/- 18 (E2) ng/liter x min. The approximate entropy (ApEn) of serial GH release [1.297 +/- 0.061 (placebo) and 1.323 +/- 0.06 (E2)] and the mesor (cosine mean), amplitude, and acrophase (time of the maximum) of 24-h rhythmic GH secretion were likewise invariant of estrogen supplementation. Estimated statistical power exceeded 90% for detecting significant (P < 0.05) within-subject changes exceeding 30-50% in the mean serum GH concentration, GH ApEn, or GH mesor. In contrast, ApEn analysis of the evolution of successive GH secretory burst-mass values over 24 h disclosed that E2 replacement disrupts the serial regularity of pulsatile GH output (elevates the ApEn ratio) during combined GHRH/GHRP-2 stimulation (P = 0.004). In summary, short-term elevation of serum E2 concentrations in postmenopausal individuals into the midfollicular phase range observed in young women does not significantly alter 24-h basal, pulsatile, entropic, or nyctohemeral GH secretion monitored under continuous combined drive by GHRH and GHRP-2. As E2 repletion without enforced GHRH/GHRP-2 stimulation augments each of the foregoing regulated facets of GH release, we infer that one or both of the infused peptidyl secretagogues may itself participate in E2's short-term amplification of GH secretion in postmenopausal individuals. Estrogen's disruption of the orderliness of sequential GH pulse-mass values during fixed GHRH/GHRP-2 feedforward would be consistent with a subtle reduction in the release and/or actions of hypothalamic somatostatin or an (unexpected) direct pituitary action of the sex steroid. Whether comparable dynamics mediate the effects of endogenous estrogen on the GH axis in premenopausal women or pubertal girls is not known.

Aged↗
PubMed1995

Regression analyses of counts and rates: Poisson, overdispersed Poisson, and negative binomial models.

The regression models appropriate for counted data have seen little use in psychology. This article describes problems that occur when ordinary linear regression is used to analyze count data and presents 3 alternative regression models. The simplest, the Poisson regression model, is likely to be misleading unless restrictive assumptions are met because individual counts are usually more variable ("overdispersed") than is implied by the model. This model can be modified in 2 ways to accomodate this problem. In the overdispersed model, a factor can be estimated that corrects the regression model's inferential statistics. In the second alternative, the negative binomial regression model, a random term reflecting unexplained between-subject differences is included in the regression model. The authors compare the advantages of these approaches.

Binomial Distribution↗
PubMed1991

Statistical analyses of enzyme inhibitor kinetics: a hierarchical model-dependent approach.

Inference of the nature of an enzyme inhibitor and calculations of inhibitor constants from linear plots are prone to be unreliable when experimental error is significant. This may be minimised by a method of statistical analysis using nonlinear regression methods and modelling using the variance ratio test of a hierarchy of models of inhibitor behaviour.

Computer Simulation↗
PubMed1992

Temporal variation in incidence of IDDM in Canterbury, New Zealand.

OBJECTIVES: To establish the statistical significance of observed variations over the last decade in the incidence of insulin-dependent diabetes mellitus (IDDM) in the 0- to 19-yr-old age-group and to determine whether incidence has increased in Canterbury, New Zealand. RESEARCH DESIGN AND METHODS: The Canterbury, New Zealand, Diabetes Registry has recorded all incidence cases of diabetes mellitus prospectively since 1982. All IDDM subjects aged 0-19 yr at diagnosis and using insulin are included in the study. Ascertainment is believed to be 100%. Prevalence was recorded at 1 January 1982 and 1 January 1990. Annual incidence for 1982-1990 was determined using age and sex cross-sectional census population denominators. The statistical significance of temporal, age, sex, and seasonal variations in incidence rates was ascertained by Poisson regression models (GLIM statistical software). RESULTS: Prevalence on 1 January 1990 was 115/100,000. Incidence rates during the 9 yr were periodic, with two major peaks--one in the early 1980s, the other in 1989 continuing into 1990. The temporal variation (P less than 0.02) was not age or sex specific. Incidence rates for boys were three- to fourfold higher during peak versus trough years, with a peak level of 20.7/100,000 in 1990. For girls, there was less variation, with a peak rate of 21.6/100,000 in 1990. There has been no significant increase in IDDM incidence over time. The mean rate of incidence across all age-groups for 1982-1990 was 12.7/100,000 person-yr. A significant seasonal association to the onset of IDDM was found only in boys, with incidence rates being significantly higher in winter than in summer (P less than 0.01). CONCLUSIONS: IDDM in Canterbury, New Zealand, presents in cycles of incidence peaks and troughs, each spanning 2-3 yr.

Adolescent↗
PubMed2000

A statistical analysis of the effect of warfare on the human secondary sex ratio.

Many factors have been hypothesized to affect the human secondary sex ratio (the annual percentage of males among all live births), among them race, parental ages, and birth order. Some authors have even proposed warfare as a factor influencing live birth sex ratios. The hypothesis that during and shortly after periods of war the human secondary sex ratio is higher has received little statistical treatment. In this paper we evaluate the war hypothesis using 3 statistical methods: linear regression, randomization, and time-series analysis. Live birth data from 10 different countries were included. Although we cannot speak of a general phenomenon, statistical evidence for an association between warfare and live birth sex ratio was found for several countries. Regression and randomization test results were in agreement. Time-series analysis showed that most human sex-ratio time series can be described by a common model. The results obtained using intervention models differed somewhat from results obtained by regression methods.

Birth Rate↗
PubMed2002

Unravelling the fetal origins hypothesis: is there really an inverse association between birthweight and subsequent blood pressure?

BACKGROUND: The association between birthweight and subsequent blood pressure levels has been considered to provide some of the strongest, and most consistent, support for the "fetal origins" hypothesis of adult disease. It had been estimated that a 1 kg higher birthweight is typically associated with a 2-4 mm Hg lower systolic blood pressure. METHODS: 55 studies that had reported regression coefficients of systolic blood pressure on birthweight (with 48 further studies that reported only the direction of this association), and seven such studies within twin pairs, were identified. Each study was weighted according to the inverse of the variance of the regression coefficient (ie, "statistical size"), and combined using a "fixed effects" approach. FINDINGS: Among the 55 studies that reported regression coefficients, there was a clear trend (p<0.0001) towards weaker associations in the larger studies: -1.9 mm Hg/kg in those with less than about 1000 participants; -1.5 mm Hg/kg with about 1000-3000 participants; and -0.6 mm Hg/kg with more than 3000 participants. By contrast with the inverse associations reported in 52 of these 55 studies, only 25 of the 48 studies that did not report regression coefficients found an inverse association (p<0.0001 for heterogeneity). Almost all of these regression coefficients had been adjusted for current weight (whereas few were adjusted for potential confounding factors), and removal of this adjustment in the larger studies reduced the estimated association to -0.4 mm Hg/kg. For studies within monozygotic twin pairs, the combined estimate was -0.6 mm Hg/kg with adjustment for current weight, and was also reduced without this adjustment. INTERPRETATION: Claims of a strong inverse association between birthweight and subsequent blood pressure may chiefly reflect the impact of random error, selective emphasis of particular results, and inappropriate adjustment for current weight and for confounding factors. These findings suggest that birthweight is of little relevance to blood pressure levels in later life.

Birth Weight↗
PubMed2006

Disease progression and survival in patients with prostate carcinoma and positive lymph nodes after radical retropubic prostatectomy.

OBJECTIVE: To determine disease progression and survival in patients with lymph node-positive prostate carcinoma after ascending radical retropubic prostatectomy (RP) and pelvic lymphadenectomy with different forms of postoperative adjuvant treatment. PATIENTS AND METHODS: We analysed 82 patients with lymph node metastases at the time of surgery and who had a RP between 1993 and 2002. Data from clinical records and follow-up questionnaires were used. Overall survival, time to clinical disease progression and time to biochemical progression were used as endpoints to assess the outcome. Clinical progression was defined as documented local recurrence or distant metastases, and biochemical as an increase in prostate-specific antigen (PSA) of > or = 0.4 ng/mL. Variables analysed included PSA level, Gleason score before and after RP, clinical and pathological stage, number of positive lymph nodes and hormone therapy after RP. The statistical assessment included univariate regression analysis, and to analyse the distribution of clinical findings in different groups, Mantel-Haenszel statistics were used to test for differences in the numbers of patients. Survival and progression-free interval were assessed by Kaplan-Meier estimates and differences between groups calculated by log-rank statistics and Cox regression models. RESULTS: The median (range) follow-up was 55 (10-125) months. Adjuvant hormonal treatment was used in 77 patients, five of whom had immediate adjuvant radiotherapy, and nine delayed radiotherapy because of local progression or symptomatic bone metastases; five had no additional treatment. The rates for 5- and 10-year overall survival, clinical progression-free survival and biochemical progression-free survival were 84% and 79%, 83% and 77%, and 70% and 60%, respectively. Ten patients died (12%), eight (10%) of them from the cancer; bone metastases were detected in nine (11%). Local recurrences developed in three (4%) patients, 10 (12%) had a PSA increase of > or = 0.4 ng/mL alone and 58 (71%) had no signs of progression, but two died from other causes. CONCLUSIONS: Most patients with prostate cancer who had RP and pelvic lymphadenectomy followed by adjuvant hormone therapy, and who had lymph node metastases at the time of surgery, had excellent overall and progression-free survival in the long term.

Adult↗
PubMed1990

A 30-year follow-up study of a child psychiatric clientele. I. Demographic description.

A register investigation was carried out as of December 31, 1980, with the aim of giving a broad description of a child psychiatric clientele 30 years after admission to hospital. The material consists of 322 patients--189 boys (59%) and 133 girls (41%)--who were admitted during the period 1949-1951 to the only 2 child psychiatric departments at that time in Denmark. We succeeded in identifying 93% of the patients. The mean age at the time of analysis was 38.6 years (range 32-46). The material was compared with the age-related Danish population by marital status, vocational education, and socioeconomic class. A total of 115 patients (36%) had been admitted to an adult psychiatric department, and 50 patients only once. A total of 95 patients (30%) had committed criminal offences and 12 had only committed traffic offences. A total of 60 patients (19%) had obtained disability pensions. During the 30-year follow-up period, 19 patients (6%) had died. A statistically significant extra mortality was found only for women. Four patients had committed suicide. By logistic regression analysis, a statistically significant correlation was found between criminal record and admission to psychiatric department and the variables: divorce, no vocational education, and lowest socioeconomic class. About 54% had managed well, judging by the variables employed.

Adult↗
PubMed1994

[Evaluation of the reproducibility of automated monocyte counting using flow cytometry and monoclonal antibodies].

PURPOSE: To compare the results of the monocyte count provided by autoanalysers with those attained with flow cytometry. MATERIAL AND METHODS: Fifty-six blood samples (EDTA-K3) from the emergency laboratory were studied. The automatic percentage of monocytes attained by four autoanalysers, STKS (Coulter-IZASA), Technicon H*2 (Bayer Diagnostics), Cell-Dyn-3000 (Abbott Diagnostics) and NE-8000 (TOA-Sysmex) was confronted with that provided by the flow cytometry analysis performed with a FACScan (Becton-Dickinson) using monoclonal antibodies of myeloid-monocytic lineage (CD14, CD16). The morphologic observation of the blood smear in accordance with the H20-A protocol of the National Committee for Clinical Laboratory Standards (NCCLS) was used as a reference method. Descriptive statistics plus linear regression analysis, along with the Student's t test for paired data were used for the statistical evaluation of the results. RESULTS: Significant correlation was found between the systems under study and the flow cytometry method: Technicon H*2 (y = 1.79 +/- 0.61x; r = 0.91, p < 0.0001), Coulter STKS (y = 0.61 +/- 0.93X; r = 0.89, p < 0.0001), Cell-Dyn 3000 (y = 0.88 + 0.64x; r = 0.78, p < 0.0001) and Sysmex NE-8000 (y = 4.60 +/- 0.33x; r = 0.52, p < 0.0001). When comparing the percentage of monocytes by means of the Student's t test it was found that Coulter STKS provided the closest results with regard to flow cytometry (13.78 +/- 9.27 vs 14.19 +/- 8.88, p = 0.49), while the closest findings with respect to the reference method were given by Technicon H*2 (9.29 +/- 4.78 vs 9.71 +/- 4.77, p = 0.30). CONCLUSIONS: From this analysis, it was concluded that flow cytometry could be an alternative method to conventional optic observation in the evaluation of the differential count of leucocytes, including monocytes.

Antibodies, Monoclonal↗
PubMed1990

Foot length growth related to crown-rump length, gestational age and weight in human staged fresh fetuses. An index for anatomical and medical use.

Several anatomical parameters are useful in the assessment of gestational age. This work studies the foot length growth analysed against age, crown-rump length (C-R) and body weight (W) in eighty human fresh fetuses (staging from 14 to 38 weeks post-conception). These data were correlated with the following statistical methods: simple regression, power formula (allometric method), exponential and reciprocal models. The foot length growth presents very high and statistically significant coefficients of correlations with fetal parameters (P less than 0.001); the allometric method was the best method for this analysis. Foot length grows with moderate (against the age and C-R) or slight (against the W) positive allometry. This study presents statistically significant curves of the foot length growth in relation to fetal parameters. These curves are useful in anatomy, forensic medicine, feto-pathology, medical imaging, obstetrics and pediatrics.

Body Height↗
PubMed1996

Regression analysis of biomedical research data based on a repeated measure or cluster sample.

Research in biology and medicine often entails estimating the effect of an exposure variable X on a response variable Y from a cluster sample, that is, where X and Y may be measured repeatedly from the same subject (cluster), or X and Y may be measured from two or more subjects based on some related grouping such as a litter or household (cluster). Typically, regression analysis of the data is performed ignoring the subject or grouping (cluster) identity. This analytical approach has two drawbacks. First, the statistical inference of the regression coefficient of Y on X (beta) ignored cluster identity will likely be biased. More serious though, is that beta ignored cluster identity will likely be quite discrepant from the average within-cluster beta. It is the latter that is of relevance to the research question. Indeed it is not clear what beta ignored cluster identity really conveys. We describe a multiple regression model for the analysis of data from a cluster sample. The model treats the cluster as a nominal confounding variable to be adjusted. The idea is to represent the cluster by a set of dummy variables to be included as explanatory variables in the regression model. This model gives the average within-cluster beta with valid statistical inference. Numeric examples were used to illustrate the application of the dummy variable multiple regression model. This statistical method can be implemented by any software package that includes multiple regression, and virtually all commercial packages include this procedure.

Cluster Analysis↗
PubMedDate not supplied

Regression analysis applied to PVC histories: a statistical procedure for evaluating antiarrhythmic drug efficacy.

Suppression of premature ventricular contractions (PVCs) is one of the goals of antiarrhythmic therapy. In a clinical trial, however, it may be difficult to distinguish antiarrhythmic drug effect from spontaneous variation in PVCs. We propose the application of linear regression to PVC histories to ascertain drug effect in individual patients. The model determines which variables are important in explaining a patient's PVCs. One such variable indicates the presence or absence of the drug; the model determines whether the drug has an effect on the patient's PVCs, while compensating for the other explanatory variables. In addition to determining the statistical significance of any drug effect, the model estimates the strength of the effect for each patient. We demonstrate the method with data from a three-day clinical trial which used 24-hour Holter monitoring. The method is flexible and can be modified to apply to any clinical study design. It allows for inferences concerning populations and subpopulations of patients.

Anti-Arrhythmia Agents↗