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PubMed2003

"Curly" wood and tiger tails: an explanation for light and dark banding with polarization in trichothiodystrophy.

The mechanism causing the tiger tail phenomenon in trichothiodystrophy (alternating light and dark banding of hair shafts when examined with polarized light) has yet to be explained with certainty. However, we propose a simple and easily tested hypothesis to explain its striking aspect. Although the hair shafts we obtained from patients with trichothiodystrophy were fairly straight, the cortical hair fibers were not. We noticed that these fibers undulate up and down (or back and forth), a feature that is easily observed because of melanin granules embedded in each fiber. The undulations correspond exactly to the banding seen with polarization. Therefore, the tiger tail phenomenon seen in trichothiodystrophy and other hair shaft disorders is caused by a regular undulation of hair fibers within the shafts. Normal hair shafts do not exhibit the phenomenon because the hair fibers are straight and parallel to the long axis of the hair. It is the regular undulation of fibers that changes the optical properties of the hair shafts and causes a predictable banding when the shafts are examined by polarized light.

Hair↗
PubMed2001

Is unplanned return to the operating room a useful quality indicator in general surgery?

HYPOTHESIS: To test our hypothesis that unplanned return to the operating room (OR) is a useful quality indicator, we examined how often and for what reasons patients go back to the OR in a broad-based general surgery practice. DESIGN AND SETTING: Prospective cohort study at a rural tertiary care center. PATIENTS: Consecutive series of 3044 patients undergoing general surgery procedures in the OR between September 1, 1998, and March 31, 2000. Information about all postoperative adverse events occurring before discharge or within 30 days (whichever was longer) was collected prospectively. Unplanned return to the OR was defined as any secondary procedure required for a complication resulting directly or indirectly from the index operation. MAIN OUTCOME MEASURES: Unplanned return to the OR, mortality, and hospital charges. RESULTS: Overall, 107 (3.5%) had an unplanned return to the OR. A relatively small number of inpatient procedures accounted for a disproportionate share of unplanned reoperations, including colon resection (18% of total reoperations), renal transplant (9%), gastric bypass (6%), and pancreatic resection (6%). As expected, hospital charges were markedly higher for patients with unplanned returns to the OR. Reoperation was also associated with higher mortality rates; statistically significant increases were noted for pancreatic resection (33% vs 3.7%; P =.04), esophagogastrectomy (100% vs 4.2%; P =.002), and laparoscopic Nissen fundoplication (50% vs 0%; P =.01). Overall, 91 reoperations (85%) were for complications occurring at the original surgical site, including those related to an anastomosis (n = 16), surgical wound (n = 21), infection (n = 16), bleeding (n = 12), and other (n = 26). CONCLUSIONS: Unplanned returns to the OR occur across a broad spectrum of general surgical procedures and carry significant implications. Because they most often reflect problems related to the procedure itself, reoperation rates may be useful for monitoring quality across hospitals and for identifying opportunities for quality improvement locally.

Colectomy↗
PubMed2001

Long-term results of metallic stents for benign biliary strictures.

BACKGROUND: Historically, surgical correction has been the treatment of choice for benign biliary strictures (BBS). Self-expandable metallic stents (MSs) have been useful for inoperable malignant biliary strictures; however, their use for BBS is controversial and their natural history unknown. HYPOTHESIS: To test our hypothesis that MSs provide only short-term benefit, we examined the long-term outcome of MSs for the treatment of BBS. Our goal was to develop a rational approach for treating BBS. DATA EXTRACTION: Between July 1990 and December 1995, 15 patients had MSs placed for BBS and have been followed up for a mean of 86.3 months (range, 55-120 months). The mean age of the patients was 66.6 years and 12 were women. Stents were placed for surgical injury in 5 patients and underlying disease in 10 patients (lithiasis, 7; pancreatitis, 2; and primary sclerosing cholangitis, 1). One or more MSs (Gianturco-Rosch "Z" for 4 patients and Wallstents for 11 patients) were placed by percutaneous, endoscopic, or combined approaches. We considered patients to have a good clinical outcome if the stent remained patent, they required 2 or fewer invasive interventions, and they had no biliary dilation on subsequent imaging. DATA SYNTHESIS: Metallic stents were successfully placed in all 15 patients, and the mean patency rate was 30.6 months (range, 7-120 months). Five patients (33%) had a good clinical result with stent patency from 55 to 120 months. Ten patients (67%) required more than 2 radiologic and/or endoscopic procedures for recurrent cholangitis and/or obstruction (range, 7-120 months). Five of the 10 patients developed complete stent obstruction at 8, 9, 10, 15, and 120 months and underwent surgical removal of the stent and bilioenteric anastomosis. Four of these 5 patients had strictures from surgical injuries. The patient who had surgical removal 10 years after MS placement developed cholangiocarcinoma. CONCLUSIONS: Surgical repair remains the treatment of choice for BBS. Metallic stents should only be considered for poor surgical candidates, intrahepatic biliary strictures, or failed attempts at surgical repair. Most patients with MSs will develop recurrent cholangitis or stent obstruction and require intervention. Chronic inflammation and obstruction may predispose the patient to cholangiocarcinoma.

Adult↗
PubMed2005

Impact of advanced age on weight loss and health benefits after laparoscopic gastric bypass.

BACKGROUND: Advanced age is considered a relative contraindication to primary bariatric surgery at some institutions. As life expectancy is steadily increasing and quality of life is improving in our elderly population, we may need to reconsider the health benefits that obese elderly patients can obtain from bariatric surgery. Therefore, we examine the operative outcomes, weight loss, reduction of comorbidities, and medication requirements in patients older than 60 years compared with those younger than 60 years undergoing laparoscopic Roux-en-Y gastric bypass. HYPOTHESIS: The null hypothesis tested in this study is that patients older than 60 years who undergo laparoscopic Roux-en-Y gastric bypass experience a medical benefit not significantly different from that experienced by younger patients in terms of the number of medications and comorbid conditions. METHODS: The number of preoperative and postoperative comorbid conditions and the medications required for those conditions were compared between consecutive patients older than 60 years and those younger than 60 years who underwent Roux-en-Y laparoscopic gastric bypass. Early operative outcomes were also assessed. RESULTS: Analysis of 110 patients younger than 60 years compared with 20 patients older than 60 years revealed no difference in complication rate or length of hospital stay. Younger patients lost more weight and had a significantly greater reduction in body mass index. Younger patients also demonstrated more complete resolution of comorbid conditions, although this difference was not significant. Older patients, who had more comorbid conditions requiring more medication at the time of surgery, experienced a greater medication reduction during follow-up, although this was not statistically significant. CONCLUSIONS: Patients of advanced age can safely undergo laparoscopic Roux-en-Y gastric bypass. Younger patients can be expected to demonstrate greater weight loss and experience more complete resolution of their comorbid conditions. Older patients demonstrated greater overall reduction in medication requirements. Therefore, patients older than 60 years can be considered good candidates for obesity surgery and can be expected to enjoy substantial health benefits similar to those experienced by younger patients.

Aged↗
PubMed2025

High-Dose vs Standard-Dose Influenza Vaccine and Cardiovascular Outcomes in Older Adults: A Prespecified Secondary Analysis of the DANFLU-2 Randomized Clinical Trial.

IMPORTANCE: The high-dose inactivated influenza vaccine (HD-IIV) has demonstrated superior protection against laboratory-confirmed influenza infection vs standard-dose IIV (SD-IIV); however, data regarding its effectiveness against cardiovascular (CV) outcomes are mainly from observational studies or specific high-risk groups. OBJECTIVE: To investigate the relative vaccine effectiveness (rVE) of HD-IIV vs SD-IIV against CV outcomes in the general older adult population in Denmark. DESIGN, SETTING, AND PARTICIPANTS: This was a prespecified secondary analysis of DANFLU-2, a pragmatic, open-label, individually randomized clinical trial (RCT) using nationwide administrative health registries in Denmark during the 2022/2023 to 2024/2025 influenza seasons. Older adults (age ≥65 years) were eligible for inclusion regardless of comorbidity. The trial design specified that if the primary end point was neutral, no hypothesis testing would be performed for secondary or exploratory end points. Data were analyzed from June 29 to August 12, 2025. INTERVENTIONS: Individual-level 1:1 randomization to HD-IIV or SD-IIV. Participants re-enrolling in additional seasons were rerandomized. MAIN OUTCOMES AND MEASURES: Severe CV outcomes were prespecified secondary and exploratory end points in the trial, occurring from 14 days after vaccination through May 31 the following year. RESULTS: A total of 332 438 participants (170 900 [51.4%] male; mean [SD] age, 73.7 [5.8] years) were randomized (166 218 to HD-IIV and 166 220 to SD-IIV), of whom 91 026 (27.4%) had a history of CV disease. HD-IIV did not significantly reduce the trial's primary end point of hospitalization for influenza or pneumonia. The incidence of hospitalization for any cardiorespiratory disease was lower in the HD-IIV group than the SD-IIV group (rVE, 5.7% [95% CI, 1.4% to 9.9%]; absolute difference, -0.13 [95% CI, -0.24 to -0.03] percentage points), and rVE did not differ by history of CV disease compared with no CV disease at baseline. Hospitalization for any CV disease occurred in fewer participants in the HD-IIV group than the SD-IIV group (rVE, 7.5% [95% CI, 1.5% to 12.5%]; absolute difference, -0.10 [95% CI, -0.18 to -0.02] percentage points) as did hospitalization for heart failure (rVE, 19.5% [95% CI, 3.3% to 33.1%]; absolute difference, -0.03 [95% CI, -0.06 to -0.01] percentage points). CONCLUSIONS AND RELEVANCE: This study found reduced incidence of cardiorespiratory hospitalization among those who received HD-IIV vs SD-IIV, driven by a lower incidence of CV hospitalizations, and particularly heart failure hospitalizations. These differences should be interpreted as exploratory findings in the setting of a large RCT with a neutral primary outcome. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05517174.

Aged↗
PubMed1996

Mesonephros has a role in limb development and is related to thalidomide embryopathy.

Recent studies have demonstrated a link between limb reduction defects and mesonephros removal [Geduspan and Solursh, 1992) Dev. Biol., 151:242-250]. However, there is some question as to whether the limb-reduction defects seen in that study resulted from the removal of mesonephros or from the formation of scar tissue medial to the limb territory. The current study was conducted to test the hypothesis that elimination of the mesonephros without producing scar tissue adjacent to the limb will adversely affect limb morphogenesis. The hypothesis was tested by the insertion of tantalum foil barriers into various levels of the intermediate mesoderm of developing chick embryos to prevent the caudal elongation of the mesonephros. Limb reduction defects were obtained when the mesonephros was prevented from forming caudal to somite 14. No limb defects were seen when a foil barrier was placed into the intermediate mesoderm at the level of somite 21 or 25. Our results support the notion that a signal from the mesonephros is necessary for normal limb development. In addition, it appears that a craniocaudal factor emanating from the mesonephros plays a role in limb development. The limb reduction defects obtained in this study were also compared to the pattern of thalidomide embryopathy in humans. There is a close correspondence between the types of limb reduction anomalies seen with thalidomide and mesonephric blocks and between the severity of defects vs. the timing of thalidomide intake or mesonephric blockage. A model for possible thalidomide embryopathy is presented.

Animals↗
PubMed2000

Digit effects produced by prenatal exposure to antiepileptic drugs.

The hypothesis tested was that digit anomalies among individuals exposed in utero to antiepileptic drugs (AED) are best identified by a systematic search, including radiographs and dermatoglyphics, rather than relying only on visual inspection. A systematic search was made for five types of digit abnormalities in 46 AED-exposed individuals ages 5-29 years in comparison with controls: visible anomalies, size of fingernails, dermal ridge patterns, length of metacarpals and phalanges, and qualitative changes in the distal phalanges. Among the AED-exposed, nail size was not decreased. However, there was a 10.8% frequency of digit anomalies, a 12% frequency of three or more arch patterns, and significant shortening and qualitative changes in the distal phalanges, all of which are consistent with the fetal effects of AED. Among the 42 individuals who underwent all evaluations, 14.3% had two or more of these abnormalities, most of which would not be identified by clinical inspection. This frequency is much higher in these AED-exposed individuals than in the general population. Radiographs in 13 individuals over a period of several years showed that the changes in the phalanges and metacarpals persisted.

Abnormalities, Drug-Induced↗
PubMed2000

Generation of PSA-reactive effector cells after vaccination with a PSA-based vaccine in patients with prostate cancer.

BACKGROUND: JBT 1001 is a vaccine used for therapy of prostate cancer (CA), which consists of recombinant prostate-specific antigen (PSA) with lipid A formulated in liposomes. Patients with prostate CA were vaccinated with JBT 1001 emulsified in mineral oil (n = 5) or with the vaccine in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) administered locally at the site of vaccination (n = 5). Frequency of PSA-reactive T cells was measured in peripheral blood mononuclear cells (PBMC) before and after immunization, using an interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay with autologous dendritic cells (DC) as antigen-presenting cells. The hypothesis tested was that PSA-based vaccines induce T cell responses to human PSA. METHODS: In order to expand precursor cells, in vitro sensitization (IVS) was performed. Microcultures of peripheral blood lymphocytes (PBL) (1 x 10(5)/well) in medium supplemented with interleukin-2 (IL-2) (10 IU/ml) and interleukin-7 (IL-7) (10 ng/ml) were stimulated twice (day 0 and day 7) with monocyte-derived autologous DC, generated by culture with interleukin-4 (IL-4) and GM-CSF and pulsed with PSA (10 microg/ml) at an effector to stimulator ratio of 10:1. ELISPOT assays were performed on day 14 of culture. In addition, PBMC were separated on immunobeads into CD4(+) and CD8(+) subsets for ELISPOT assays performed without IVS. RESULTS: Two patients had PSA-reactive responses before vaccination (frequency range, 1/700-1/4,400). After vaccination, 8/10 patients had measurable PSA-reactive T-cell frequencies, ranging from 1/200-1/1900, using IVS. In contrast, without IVS, but after immunoselection to enrich in CD8(+) and CD4(+) T cells, only 2/10 patients had detectable PSA-reactive T cells after vaccination, at a frequency ranging from 1/2,600-1/4,000. CONCLUSIONS: Vaccination with PSA formulated into liposomes induced T-cell responses in 8/10 patients with prostate carcinoma. The frequency of PSA-reactive precursor T cells was relatively low in the blood of these patients, and IVS, leading to amplification of the precursor cells prior to ELISPOT, was necessary for quantification of the PSA-responding T cells. Cellular responses to PSA were predominantly mediated by CD4(+) T lymphocytes.

Aged↗
PubMed1997

Comparative calibration without a gold standard.

Comparative calibration is the broad statistical methodology used to assess the calibration of a set of p instruments, each designed to measure the same characteristic, on a common group of individuals. Different from the usual calibration problem, the true underlying quantity measured is unobservable. Many authors have shown that this problem, in general, does not have a unique solution. Most commonly used assumptions to obtain a unique solution are (i) one instrument is the gold standard (that is, unbiased) and (ii) the measurement errors of the p instruments are independent. Such constraints, however, may not be valid for many clinical applications, for example, the universal standardization project for dual X-ray absorptiometry (DXA) scanners. In this paper, we propose a new approach to resolve the comparative calibration problem when a gold standard is unavailable. Instead of the usual assumptions, we use external information in addition to data from the p instruments, to solve the problem. We address statistical estimation, hypothesis testing and missing data problems. We apply the new method specifically to the universal standardization project data where a group of individuals have been measured for bone mineral density (BMD) by three DXA scanners. We compare the results of the new method to currently used methods and show that they have better statistical properties.

Absorptiometry, Photon↗
PubMed1997

Controlling false positive rates in prognostic factor analyses with small samples.

Exploratory data analyses in medical research usually involve many potential risk factors. Typically, one performs numerous hypothesis tests to identify variables that are of prognostic value. Because of the multiplicity of tests, one must control the overall false positive rate. The Bonferroni adjustment is simple to use, but may be overly conservative when applied to correlated tests. We propose an exact adjustment method, based on the joint permutational distributions of the test statistics, in settings where the acquired sample size only allows analysis of a single feature at a time. We demonstrate our method with two examples.

Adolescent↗
PubMedDate not supplied

Identifying the types of missingness in quality of life data from clinical trials.

This paper discusses methods of identifying the types of missingness in quality of life (QOL) data in cancer clinical trials. The first approach involves collecting information on why the QOL questionnaires were not completed. Based on the reasons provided one may be able to distinguish the mechanisms causing missing data. The second approach is to model the missing data mechanism and perform hypothesis testing to determine the missing data processes. Two methods of testing if missing data are missing completely at random (MCAR) are presented and applied to incomplete longitudinal QOL data obtained from international multi-centre cancer clinical trials. The first method (Ridout, 1991) is based on a logistic regression and the second method (Park and Davis, 1993) is based on an adaptation of weighted least squares. In one application (advanced breast cancer) missing data was not likely to be MCAR. In the second application (adjuvant breast cancer) the missing mechanism was dependent on the QOL scale under study. MCAR and missing at random (MAR) have distinct consequences for data analysis. Therefore it is relevant to distinguish between them. However, if either MCAR or MAR hold, likelihood or Bayesian inferences can be based solely on the observed data, although for MAR, depending on the research question, modelling the dropout mechanism may still be necessary. Distinguishing between MAR and missing not at random (MNAR) is not trivial and relies on fundamentally untestable assumptions.

Clinical Trials as Topic↗
PubMedDate not supplied

Comparison of several model-based methods for analysing incomplete quality of life data in cancer clinical trials.

This paper considers five methods of analysis of longitudinal assessment of health related quality of life (QOL) in two clinical trials of cancer therapy. The primary difference in the two trials is the proportion of participants who experience disease progression or death during the period of QOL assessments. The sensitivity of estimation of parameters and hypothesis tests to the potential bias as a consequence of the assumptions of missing completely at random (MCAR), missing at random (MAR) and non-ignorable mechanisms are examined. The methods include complete case analysis (MCAR), mixed-effects models (MAR), a joint mixed-effects and survival model and a pattern-mixture model. Complete case analysis overestimated QOL in both trials. In the adjuvant breast cancer trial, with 15 per cent disease progression, estimates were consistent across the remaining four methods. In the advanced non-small-cell lung cancer trial, with 35 per cent mortality, estimates were sensitive to the missing data assumptions and methods of analysis.

Breast Neoplasms↗
PubMedDate not supplied

Issues for statisticians in pharmaco-economic evaluations.

Economic evaluations of new pharmaceutical products are of increasing importance to pharmaceutical companies. In this paper we investigate a number of topics of greater or lesser importance to statisticians who need to involve themselves in pharmaco-economic evaluations. These range from the need to consider whether traditional randomized clinical trials provide the most appropriate setting for an economic evaluation, to the more technical question of how to handle cost-effectiveness ratio data, including the issue of the most appropriate inferential apparatus-hypothesis testing, confidence intervals or Bayesian methods.

Bayes Theorem↗
PubMedDate not supplied

A framework establishing clear decision criteria for the assessment of drug efficacy.

Much has been published on various aspects of data analysis and reporting from clinical trials within the biopharmaceutical environment. This ranges from regulatory guidelines on the format and content of registration dossiers to recommendations on data presentation and the statistical methodologies that are appropriate for the diverse types of data one observes in clinical trials. Little has been written about designing a clinical trial analysis and reporting package that focuses on the decisions that must be made throughout the drug development process. Pharmaceutical companies today are under enormous pressure to develop drugs quickly and (cost-) efficiently. Because of this, drugs often move into the later phases of drug development before evidence from prior phases is completely understood. This provides a challenge to clinical trialists to design and execute a clinical trial programme which can expedite drug development. The statistician, as a clinical trialist, must strive to determine the optimum analytical methodology that facilitates decision making for this clinical trial programme. This paper proposes a new framework for the assessment of efficacy in drug development called the 'one programme, one p-value' framework. This framework will accelerate drug development by providing clear criteria for the decisions which must be made along the way. The 'one programme, one p-value' framework is based on the notion that the clinical trial programme comprises exploratory and confirmatory phases. The use of the likelihood function in the exploratory phase facilitates the decision whether (or when) to move into the confirmatory phase. The confirmatory phase consists of one confirmatory trial with a single hypothesis test of the drug's efficacy; hence 'one p-value'. Sponsor interaction with regulatory agencies is necessary at each decision point. Finally, the paper considers how analysis and reporting of efficacy data can be accomplished from a clinical trial programme as described.

Clinical Trials as Topic↗
PubMed1999

Tutorial in biostatistics. An introduction to hierarchical linear modelling.

Hierarchical linear models are useful for understanding relationships in hierarchical data structures, such as patients within hospitals or physicians within hospitals. In this tutorial we provide an introduction to the technique in general terms, and then specify model notation and assumptions in detail. We describe estimation techniques and hypothesis testing procedures for the three types of parameters involved in hierarchical linear models: fixed effects, covariance components, and random effects. We illustrate the application using an example from the Type II Diabetes Patient Outcomes Research Team (PORT) study and use two popular PC-based statistical computing packages, HLM/2L and SAS Proc Mixed, to perform two-level hierarchical analysis. We compare output from the two packages applied to our example data as well as to simulated data. We elaborate on model interpretation and provide guidelines for model checking.

Adult↗
PubMed1999

Multivariate outlier detection applied to multiply imputed laboratory data.

In clinical laboratory safety data, multivariate outlier detection methods may highlight a patient whose laboratory measurements do not follow the same pattern of relationships as the majority of patients, although their individual measurements are not found to be outlying when considered one at a time. Missing data problems are often dealt with by imputing a single value as an estimate of the missing value. The completed data set may then be analysed using traditional methods. A disadvantage of using single imputation is the underestimation of variability, with a corresponding distortion of power in hypothesis testing. Multiple imputation methods attempt to overcome this problem, and in this paper a study is described which considers the application of multivariate outlier detection methods to multiply imputed clinical laboratory safety data sets. Three different proportions of missing data are generated in laboratory data sets of dimensions 4, 7, 12 and 30, and a comparison of eight multiple imputation methods is carried out. Two outlier detection techniques, Mahalanobis distance and generalized principal component analysis, are applied to the multiply imputed data sets, and their performances are discussed. Measures are introduced for assessing the accuracy of the missing data results, depending on which method of analysis is used.

Algorithms↗
PubMedDate not supplied

Marginal modelling of multivariate categorical data.

This paper describes likelihood methods of analysis for multivariate categorical data. The joint distribution is specified in terms of marginal mean functions, and pairwise and higher order association measures. For the association, the emphasis is on global odds ratios. The method allows flexible formulation of a broad class of designs, such as repeated measurements, longitudinal studies, interrater agreement and cross-over trials. The proposed model can be used for parameter estimation and hypothesis testing. Simple fitting algorithms are proposed. The method is illustrated using a data example.

Adolescent↗
PubMedDate not supplied

Statistics versus statistical science in the regulatory process.

This paper reviews the established practice of providing evidence to regulatory authorities about the claimed properties (such as efficacy and safety) of new pharmaceutical products. The established conventions and procedures are contrasted with scientific concepts and principles. The following issues are discussed: (a) recruitment of subjects and its connection to treatment heterogeneity; (b) the measurement process and the handling of missing data; (c) data transformation and the use of generalized linear models; (d) model selection and model checking; (e) the 'cult of the single trial' and the use of prior information; and (f) hypothesis testing and the P-value culture.

Area Under Curve↗