Variability in the diagnosis of surgical-site infections after full-thickness skin grafting: an international survey.

BACKGROUND: Diagnosis of a surgical-site infection (SSI) in dermatological surgery can be based entirely on a subjective assessment, according to the fourth criterion of the most common definition of an SSI, which was established by the US Centers for Disease Control and Prevention. OBJECTIVES: To investigate the interobserver agreement between dermatologists in their diagnosis of SSI of dermatosurgical wounds. METHODS: An international electronic photographic survey with eight photographs of wounds 1 week after full-thickness skin grafting (FTSG) was sent to dermatologists. All wounds were assessed in terms of visual criteria beforehand. Data collected from respondents included physician characteristics and experience, and SSI assessments of all wounds. RESULTS: In total, 393 dermatologists from 27 countries enrolled. Most respondents were from the U.S.A. (25%), followed by Sweden (24%) and the U.K. (13%). There was only a slight interobserver agreement on SSI suspicion (κ = 0·19). SSI suspicion was lower for male physicians (P = 0·03), board-certified dermatologists (P = 0·001), physicians regularly assessing surgical wounds (P = 0·03) and physicians performing FTSG (P < 0·001). Swedish physicians diagnosed more SSIs than U.S. physicians (P = 0·002). Erythema was more common in cases with higher SSI suspicion. CONCLUSIONS: This study reveals broad inter-rater variability in the diagnosis of SSI, illustrating the need for novel objective diagnostic methods that can better capture the variables that constitute an SSI.

A bivariate survival model with compound Poisson frailty.

A correlated frailty model is suggested for analysis of bivariate time-to-event data. The model is an extension of the correlated power variance function (PVF) frailty model (correlated three-parameter frailty model) (J. Epidemiol. Biostat. 1999; 4:53-60). It is based on a bivariate extension of the compound Poisson frailty model in univariate survival analysis (Ann. Appl. Probab. 1992; 4:951-972). It allows for a non-susceptible fraction (of zero frailty) in the population, overcoming the common assumption in survival analysis that all individuals are susceptible to the event under study. The model contains the correlated gamma frailty model and the correlated inverse Gaussian frailty model as special cases. A maximum likelihood estimation procedure for the parameters is presented and its properties are studied in a small simulation study. This model is applied to breast cancer incidence data of Swedish twins. The proportion of women susceptible to breast cancer is estimated to be 15 per cent.

The impact of HLA-A and -DRB1 on age at onset, disease course and severity in Scandinavian multiple sclerosis patients.

The human leucocyte antigen (HLA) class II haplotype DRB1*15-DQB1*06 (DR15-DQ6) is associated with susceptibility to multiple sclerosis (MS), and HLA class I associations in MS have also been reported. However, the influence of HLA class I and II alleles on clinical phenotypes in MS has not yet been completely studied. This study aimed at evaluating the impact of HLA-A and -DRB1 alleles on clinical variables in Scandinavian MS patients. The correlation between HLA-A or -DRB1 alleles and age at onset, disease course and Multiple Sclerosis Severity Score (MSSS) were studied in 1457 Norwegian and Swedish MS patients by regression analyses and Kruskal-Wallis rank sum test. Presence of HLA-DRB1*15 was correlated with younger age at onset of disease (corrected P = 0.009). No correlation was found between HLA-A and the variables studied. This study analysed the effect of HLA-A on clinical variables in a large Scandinavian sample set, but could not identify any significant contribution from HLA-A on the clinical phenotype in MS. However, associations between HLA-DRB1*15 and age at onset of MS were reproduced in this extended Scandinavian MS cohort.

Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance.

BACKGROUND: Experimental and epidemiologic investigations suggest that alpha-tocopherol (the most prevalent chemical form of vitamin E found in vegetable oils, seeds, grains, nuts, and other foods) and beta-carotene (a plant pigment and major precursor of vitamin A found in many yellow, orange, and dark-green, leafy vegetables and some fruit) might reduce the risk of cancer, particularly lung cancer. The initial findings of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study) indicated, however, that lung cancer incidence was increased among participants who received beta-carotene as a supplement. Similar results were recently reported by the Beta-Carotene and Retinol Efficacy Trial (CARET), which tested a combination of beta-carotene and vitamin A. PURPOSE: We examined the effects of alpha-tocopherol and beta-carotene supplementation on the incidence of lung cancer across subgroups of participants in the ATBC Study defined by base-line characteristics (e.g., age, number of cigarettes smoked, dietary or serum vitamin status, and alcohol consumption), by study compliance, and in relation to clinical factors, such as disease stage and histologic type. Our primary purpose was to determine whether the pattern of intervention effects across subgroups could facilitate further interpretation of the main ATBC Study results and shed light on potential mechanisms of action and relevance to other populations. METHODS: A total of 29,133 men aged 50-69 years who smoked five or more cigarettes daily were randomly assigned to receive alpha-tocopherol (50 mg), beta-carotene (20 mg), alpha-tocopherol and beta-carotene, or a placebo daily for 5-8 years (median, 6.1 years). Data regarding smoking and other risk factors for lung cancer and dietary factors were obtained at study entry, along with measurements of serum levels of alpha-tocopherol and beta-carotene. Incident cases of lung cancer (n = 894) were identified through the Finnish Cancer Registry and death certificates. Each lung cancer diagnosis was independently confirmed, and histology or cytology was available for 94% of the cases. Intervention effects were evaluated by use of survival analysis and proportional hazards models. All P values were derived from two-sided statistical tests. RESULTS: No overall effect was observed for lung cancer from alpha-tocopherol supplementation (relative risk [RR] = 0.99; 95% confidence interval [CI] = 0.87-1.13; P = .86, logrank test). beta-Carotene supplementation was associated with increased lung cancer risk (RR = 1.16; 95% CI = 1.02-1.33; P = .02, logrank test). The beta-carotene effect appeared stronger, but not substantially different, in participants who smoked at least 20 cigarettes daily (RR = 1.25; 95% CI = 1.07-1.46) compared with those who smoked five to 19 cigarettes daily (RR = 0.97; 95% CI = 0.76-1.23) and in those with a higher alcohol intake (> or = 11 g of ethanol/day [just under one drink per day]; RR = 1.35; 95% CI = 1.01-1.81) compared with those with a lower intake (RR = 1.03; 95% CI = 0.85-1.24). CONCLUSIONS: Supplementation with alpha-tocopherol or beta-carotene does not prevent lung cancer in older men who smoke. beta-Carotene supplementation at pharmacologic levels may modestly increase lung cancer incidence in cigarette smokers, and this effect may be associated with heavier smoking and higher alcohol intake. IMPLICATIONS: While the most direct way to reduce lung cancer risk is not to smoke tobacco, smokers should avoid high-dose beta-carotene supplementation.

Effects of alpha-tocopherol and beta-carotene supplements on cancer incidence in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study.

The Alpha-Tocopherol Beta-Carotene (ATBC) Cancer Prevention Study was a placebo-controlled, randomized intervention trial testing the hypothesis that beta-carotene and alpha-tocopherol (vitamin E) supplements prevent lung and other cancers. The study is predicated on a substantial body of evidence supporting a role in cancer prevention for these micronutrients. Based on the 2 x 2 factorial study design, 29,133 eligible male cigarette smokers aged 50-69 y were randomly assigned to receive beta-carotene (20 mg), alpha-tocopherol (50 mg), beta-carotene and alpha-tocopherol, or placebo daily for 5-8 y. Capsule compliance was high (median = 99%). beta-Carotene treatment did not result in a decrease in cancer at any of the major sites but rather in an increase at several sites, most notably lung, prostate, and stomach (number of cases 474 compared with 402, 138 compared with 112, and 70 compared with 56, respectively). The vitamin E group had fewer incident cancers of the prostate and colorectum compared with the group not receiving vitamin E (number of cases 99 compared with 151 and 68 compared with 81, respectively), but more cancers of the stomach (70 compared with 56). In contrast to these intervention-based findings for beta-carotene and vitamin E supplements, we observed lower lung cancer rates in men with higher amounts of both serum and dietary beta-carotene and vitamin E at baseline.

Prognosis of patients with lung cancer found in a single chest radiograph screening.

BACKGROUND: The prognosis of patients with lung cancer is better when the diagnosis is made early; the disease is localized, and radical surgery is possible. Screening for lung cancer with mass radiography or sputum cytology should contribute to a more favorable prognosis. Large-scale screening studies have improved the survival rates for lung cancer but have yielded no reduction in mortality rates. METHODS: The histologic types, stages, treatments, and survival rates were studied in 93 men who were found to have lung cancer in a single chest radiograph screening of more than 33,000 men who smoked and were 50 to 69 years old ("screened cases"), and in 239 men of the same age range whose lung cancer was detected through ordinary health care system ("other cases") during the screening period. RESULTS: The distribution of the histology was similar in the two groups, but screening detected more instances of early-stage disease that were resectable more often than in the other group (37 vs 19%). The 5-year survival rate for men in the screened cases was 19%, and that of men in the other cases was 10% (relative risk, 0.65; 95% confidence interval [CI], 0.50 to 0.84). The survival rate of men in the screened cases remained significantly higher than that of men in the other cases even after adjustments for age, smoking status, histology, stage of the disease, and resectability of the disease (relative risk, 0.74; 95% CI, 0.55 to 1.00). CONCLUSIONS: According to this study, chest radiograph screening might improve the prognosis of lung cancer. Our results are, however, subject to many factors that were only partially controlled for, and they should be interpreted cautiously.

Body site of cutaneous malignant melanoma--a study on patients with hereditary and multiple sporadic tumours.

Individuals with an increased risk of developing cutaneous malignant melanoma (CMM) include members of kindreds with hereditary cutaneous malignant melanoma (HCMM) and patients who have already been treated for a CMM. Some of these patients develop multiple primary cutaneous malignant melanomas (MCMMs). Ultraviolet radiation is the main instigator of CMM. There are indications that patients in these high-risk groups react differently to sunlight than patients who develop a single sporadic CMM. The objectives of this study were to analyse tumour site in patients with HCMM and sporadic MCMM. Data on 2517 patients with 2608 CMMs from a population-based regional cancer registry were used. The new computer program EssDoll was used for the analyses of primary tumour sites. This software is able to analyse any chosen body area(s) with reference to the number of tumours arising there. When the site of the first and second tumours in patients with sporadic MCMM were analysed in a skin 'field division', there was a significant concordance with respect to site (P < 0.0001). In patients with MCMM, the second primary tumour was significantly thinner than the first (P = 0.001). Primary tumour sites in patients with HCMM were compared with those in patients with a single sporadic CMM. In HCMM we found significantly fewer tumours in the head and neck area and more on the trunk. These differences remained significant in two different body area models, even when stratified for age (P < 0.05). In conclusion, a site-concordance was noted for sporadic MCMM. This may be the result of a 'field effect'. Our results indicate that intermittent ultraviolet exposure may be of relatively greater importance than chronic exposure in HCMM.

Controlling for total energy intake in regression models for assessing macronutrient effects on disease.

This paper illustrates the relationships between the (i) the standard multivariate method, (ii) the energy-adjusted method and (iii) the energy decomposition method for controlling for total energy intake. The setting is a general regression model which includes linear, logistic and Cox regressions. The discussion is confined to effects of macronutrients and to situations in which total energy intake is associated with disease. Pike, Bernstein & Peters [(1989) Am. J. Epidemiol. 129, 1312-1313] show how the three methods relate to each other and that the choice between them is a matter of taste. Here the relationships are illustrated using Venn-type diagrams. However, the rationale for all current controlling procedures relies on the assumption of external factors acting uniformly over different sources of energy. This assumption should be challenged. Furthermore, if individual macronutrients have independent, possibly even opposite effects on the risk for disease, then adjustment of any one of them will be relative to the effect of the others. This might not be satisfactory. Current methodology does not resolve these problems, and more elaborate data as well as further thought is needed.

Serum beta-carotene before and after beta-carotene supplementation.

A two-month double-blind, placebo-controlled supplementation study of oral beta-carotene (20 mg daily) was conducted. Two hundred and twenty two 30-69 year old men were randomized into either a beta-carotene or placebo group, and serum samples were obtained at baseline, follow-up (2 months), and up to 12 weeks post-supplementation. Serum beta-carotene increased on average 10-fold in the beta-carotene group, from 0.53 +/- 0.32 mumol/l (mean +/- SD) at baseline to 4.99 +/- 2.47 mumol/l at follow-up (P less than 0.0001), and beta-carotene levels remained elevated up to 12 weeks post-supplementation (0.61 +/- 0.15 mumol/l). No changes in serum retinol, alpha-tocopherol, or total cholesterol were observed. At baseline, serum beta-carotene levels were positively correlated with dietary beta-carotene (r = 0.29) and inversely correlated with body mass index and serum gamma-glutamyltransferase (r = -0.33 and r = -0.40, respectively). The inverse association with body mass index and serum gamma-glutamyltransferase persisted during active supplementation, whereas the positive association with dietary beta-carotene disappeared. In multivariate analysis, serum cholesterol was also positively associated with serum beta-carotene levels both before and after supplementation. Baseline serum beta-carotene was the factor most strongly associated (positively) with serum beta-carotene after supplementation. Our study highlights the importance of several factors which affect serum beta-carotene.

Exponential family models and statistical genetics.

This article describes the evolution of applied exponential family models, starting at 1972, the year of publication of the seminal papers on generalized linear models and on Cox regression, and leading to multivariate (i) marginal models and inference based on estimating equations and (ii) random effects models and Bayesian simulation-based posterior inference. By referring to recent work in genetic epidemiology, on semiparametric methods for linkage analysis and on transmission/disequilibrium tests for haplotype transmission this paper illustrates the potential for the recent advances in applied probability and statistics to contribute to new and unified tools for statistical genetics. Finally, it is emphasized that there is a need for well-defined postgraduate education paths in medical statistics in the year 2000 and thereafter.

Exercise, smoking, and calcium intake during adolescence and early adulthood as determinants of peak bone mass. Cardiovascular Risk in Young Finns Study Group.

OBJECTIVE: To evaluate the contribution to peak bone mass of exercise, smoking, and calcium intake in adolescents and young adults. DESIGN: Prospective cohort study with end point measurement (bone mineral density) after 11 years' follow up for lifestyle. SETTING: Five university hospital clinics. SUBJECTS: 264 (153 females, 111 males) subjects aged 9 to 18 years at the beginning of the follow up and 20 to 29 years at the time of measurement of bone mineral density. MAIN OUTCOME MEASURE: Bone mineral density of lumbar spine and femoral neck by dual energy x ray absorptiometry; measures of physical activity and smoking and estimates of calcium intake repeated three times during follow up. RESULTS: In the groups with the lowest and highest levels of exercise the femoral bone mineral densities (adjusted for age and weight) were 0.918 and 0.988 g/cm2 for women (P = 0.015, analysis of covariance) and 0.943 and 1.042 g/cm2 for men (P = 0.005), respectively; at the lumbar spine the respective values were 1.045 and 1.131 (P = 0.005) for men. In men the femoral bone mineral densities (adjusted for age, weight, and exercise) were 1.022 and 0.923 g/cm2 for the groups with the lowest and highest values of smoking index (P = 0.054, analysis of covariance). In women the adjusted femoral bone mineral density increased by 4.7% together with increasing calcium intake (P = 0.089, analysis of covariance). In multiple regression analysis on bone mineral density of the femoral neck, weight, exercise, age, and smoking were independent predictors for men; with weight, exercise, and age for women. These predictors together explained 38% of the variance in bone mineral density in women and 46% in men. At the lumbar spine, weight, smoking, and exercise were predictors for men; and only weight for women. CONCLUSIONS: Regular exercise and not smoking is important in achieving maximal peak bone mass in adolescents and young adults.

Estimation of multivariate frailty models using penalized partial likelihood.

There exists a growing literature on the estimation of gamma distributed multiplicative shared frailty models. There is, however, often a need to model more complicated frailty structures, but attempts to extend gamma frailties run into complications. Motivated by hip replacement data with a more complicated dependence structure, we propose a model based on multiplicative frailties with a multivariate log-normal joint distribution. We give a justification and an estimation procedure for this generally structured frailty model, which is a generalization of the one presented by McGilchrist (1993, Biometrics 49, 221-225). The estimation is based on Laplace approximation of the likelihood function. This leads to estimating equations based on a penalized fixed effects partial likelihood, where the marginal distribution of the frailty terms determines the penalty term. The tuning parameters of the penalty function, i.e., the frailty variances, are estimated by maximizing an approximate profile likelihood. The performance of the approximation is evaluated by simulation, and the frailty model is fitted to the hip replacement data.

Venous circulation in the maternal lower limb: a Doppler study with the Valsalva maneuver.

In order to evaluate the normal physiology of the maternal venous circulation, Doppler examinations of the venous system in the right inferior extremity and suprainguinal part of the common femoral vein were carried out in 38 healthy pregnant women, in 12 non-pregnant controls and in 16 women at early puerperium. Examinations were carried out when the mother was lying in a left semi-recumbent supine position. Blood flow velocities in the suprainguinal femoral and deep femoral veins decreased significantly in the first trimester and were almost normalized by the third postpartum day. Continuous forward venous flow with respiratory fluctuation was maintained in the femoral veins over the whole gestational period. The response to the Valsalva maneuver was similar in the pregnant and non-pregnant women. Our findings provide evidence that the venous valvular system and wall distensibility in the femoral area and the inferior extremity are in vivo not greatly changed in pregnancy. A more important reason for decreased velocities is probably the pregnancy-associated decrease of the arterial input to this area.

Repair of orbital floor fractures with bioactive glass implants.

PURPOSE: The ideal management of orbital floor fractures has been highly controversial. Many implants, both autogenous and alloplastic, have been used to span the defects. This study evaluated the use of bioactive glass implants (BAG-implant, S53P4; Abmin Technologies Ltd, Turku, Finland) for the repair of orbital floor defects caused by blunt facial trauma. PATIENTS AND METHODS: This retrospective review of 36 patients was carried out from 1995 to 1999. All patients were diagnosed with an orbital floor fracture or a large orbital blowout fracture. The BAG-implant was placed over the defect, using a subciliary or transconjunctival approach. No screw fixation was used when the implant was the correct size. Follow-up examination was done at 1 and 3 months after surgery. Twenty-eight (82%) of the patients were also seen at one-year follow-up (21 men and 7 women). RESULTS: The implants did not cause a foreign body reaction in the bone or soft tissue. There was no sign of resorption or infection, nor postoperative extrusion, hemorrhage, or displacement of the implant. Diplopia was seen preoperatively in 17 cases (61%) and postoperatively in 5 cases (18%). In 1 patient, the implant was removed 3 months after operation because of diplopia. Infraorbital nerve paresthesia was seen preoperatively in 9 patients (32%) and postoperatively in 5 patients (18%). The functional and cosmetic results were good at the 1-year follow-up. CONCLUSION: The BAG-implant is a well-tolerated material in orbital floor reconstruction. It provides a favorable environment for an uncomplicated healing process because it is bioactive and biocompatible and because it causes new bone formation.

Vitamin A and infant mortality: beyond intention-to-treat in a randomized trial.

This paper investigates the effect of one dose of vitamin A on subsequent 4 month mortality in children under 6 months of age in a randomized, double-blind placebo-controlled community trial in Nepal. An earlier published intention-to-treat analysis showed no benefit, but ignored the information on actual receipt of treatment. Structural failure time models (Robins and Tsiatis, '91) use randomization based inference and incorporate compliance information which is possibly selective. The data presented here offer some new challenges for this approach: ward-based randomization induces correlation between survival outcomes; and the actual receipt of vitamin A dose is not always recorded. To tackle the problem of the clustered survival data we consider a robust version of the structural parameter vector estimator. A sensitivity analysis captures boundaries for the estimated structural parameters reflecting a range of potential values of children whose true receipt of treatment is unknown. The analysis suggests that the effect of vitamin A was beneficial in the beginning of the trial but towards the end of the trial there was a reversal of this effect.

Correcting for non-compliance in randomized trials: an application to the ATBC Study.

Different methods for estimating the effect of treatment actually received in a longitudinal placebo-controlled trial with non-compliance are discussed. Total mortality from the ATBC Study is used as an illustrative example. In the ATBC Study some 25 per cent of the participants dropped out from active follow-up prior to the scheduled end of the study. The 'intention-to-treat' analysis showed an increased death risk in the beta-carotene arm when compared with the no beta-carotene arm. Owing to considerable non-compliance it is also of interest to estimate the effect of beta-carotene actually received. We use a simple model for the treatment action and discuss three methods for estimation of the treatment effect under the model - the 'intention-to-treat' approach, the 'as-treated' approach and the g-estimation approach. These approaches are compared in a simulation study under different settings for non-compliance. Finally, the data from the ATBC Study are analysed using the proposed methods.

Virulence-associated characteristics of Escherichia coli in urinary tract infection: a statistical analysis with special attention to type 1C fimbriation.

The relative virulence (defined as odds ratio) associated with different O and K antigens, adhesins and hemolysin production of Escherichia coli strains was assessed by separate and multivariate logistic regression analyses comparing 383 strains isolated from urine of adults with a urinary tract infection with 287 fecal strains from healthy adults; special interest was paid to evaluating the role of type 1C fimbriation. Type 1C fimbriae, found on 14% of UTI and 7% of fecal strains, were associated with O groups O2, O6, O18, and O75, with capsular type K5, with mannose-resistant (both P and non-P) adhesins, and with hemolysin production. In separate analyses, O8 (odds ratio 5.9) and O75 (9.2), capsular types other than K1 (1.9-2.1), P (2.9) and non-P mannose-resistant (17.4) adhesins, and hemolysin production (3.1) were each associated with high relative virulence compared to O1, Rough, and K1 phenotypes or lack of mannose-resistant adhesins or hemolysin. All these virulence effects were independent of type 1C fimbriation. In multivariate analysis, joint variation between factors decreased the apparent virulence-promoting effect of type 1C fimbriae, O6 antigen and hemolysin but increased that of other adhesins. Especially high relative virulence (odds ratio 404.2) was associated with the combination of O75:K5:non-P mannose-resistant adhesin identified on seven UTI but no fecal strains.

Sinistrality--a side-effect of prenatal sonography: a comparative study of young men.

Although ultrasound during pregnancy is used extensively, there is little published on adverse fetal effects. We undertook a cohort study including men born in Sweden from 1973 to 1978 who enrolled for military service. We estimated relative risks for being born left-handed according to ultrasound exposure in fetal life using logistic regression analysis. Eligible for the study were 6,858 men born at a hospital that included ultrasound scanning in standard antenatal care (exposed) and 172,537 men born in hospitals without ultrasound scanning programs (unexposed). During the introduction phase (1973 to 1975) there was no difference in left-handedness between ultrasound exposed and unexposed (odds ratio = 1.03, 95% confidence interval (CI) = 0.91 to 1.17). When ultrasonography was offered more widely (1976 to 1978), the risk of left-handedness was higher among those exposed to ultrasound compared with those unexposed (odds ratio = 1.32, 95% CI = 1.16 to 1.51). We conclude that ultrasound exposure in fetal life increases the risk of left-handedness in men, suggesting that prenatal ultrasound affects the fetal brain.

Body-size indicators and risk of breast cancer according to menopause and estrogen-receptor status.

Associations between the risk of breast cancer and body-size indicators at the time of breast-cancer diagnosis were assessed among 328 pre-menopausal or post-menopausal cases and 417 controls participating in the Kuopio Breast Cancer Study. This case-control study follows the protocol of the international Collaborative Study of Breast and Colorectal Cancer. When the potential confounding factors were taken into account, tallness was related to increased risk of breast cancer, especially in post-menopausal women, whereas no clear association with body-mass index (BMI) was found. Waist-to-hip ratio (WHR) was the most important risk factor in both pre-menopausal and post-menopausal women. The post-menopausal cases with high positive estrogen-receptor status (ER++) had the highest weight and BMI; they had also the biggest weight gain since the age of 20. However, the association between WHR and breast cancer appeared to be independent of estrogen-receptor status. Our results suggest that WHR may be a better marker for breast cancer than the degree of adiposity.