Approaches to accommodate noisy data in the direct solution of inverse problems in incompressible plane-strain elasticity.

We apply the adjoint weighted equation method (AWE) to the direct solution of inverse problems of incompressible plane strain elasticity. We show that based on untreated noisy displacements, the reconstruction of the shear modulus can be very poor. We link this poor performance to loss of coercivity of the weak form when treating problems with discontinuous coefficients. We demonstrate that by smoothing the displacements and appending a regularization term to the AWE formulation, a dramatic improvement in the reconstruction can be achieved. With these improvements, the advantages of the AWE method as a direct solution approach can be extended to a wider range of problems.

Investigating the impact of spatial priors on the performance of model-based IVUS elastography.

This paper describes methods that provide pre-requisite information for computing circumferential stress in modulus elastograms recovered from vascular tissue-information that could help cardiologists detect life-threatening plaques and predict their propensity to rupture. The modulus recovery process is an ill-posed problem; therefore, additional information is needed to provide useful elastograms. In this work, prior geometrical information was used to impose hard or soft constraints on the reconstruction process. We conducted simulation and phantom studies to evaluate and compare modulus elastograms computed with soft and hard constraints versus those computed without any prior information. The results revealed that (1) the contrast-to-noise ratio of modulus elastograms achieved using the soft prior and hard prior reconstruction methods exceeded those computed without any prior information; (2) the soft prior and hard prior reconstruction methods could tolerate up to 8% measurement noise, and (3) the performance of soft and hard prior modulus elastograms degraded when incomplete spatial priors were employed. This work demonstrates that including spatial priors in the reconstruction process should improve the performance of model-based elastography, and the soft prior approach should enhance the robustness of the reconstruction process to errors in the geometrical information.

Risk factors and recommendations for rate stratification for surveillance of neonatal healthcare-associated bloodstream infection.

Neonates are among the most vulnerable patient groups for healthcare-associated infection with multiple endogenous and exogenous risks. Interpretation of neonatal bloodstream infection (BSI) rates requires stratification for case-mix. We assessed 1367 consecutive admissions to a single neonatal unit over a 34-month period. Four intrinsic and seven extrinsic risks were evaluated using Poisson regression analyses both individually and in combination. Nine of the 11 evaluated risk factors were significantly associated with BSI on univariate analyses. The only significant independent risks were parenteral nutrition, whether administered centrally or peripherally [incidence rate ratio (IRR): 14.2; 95% confidence interval (CI): 8.8-22.9; P<0.001], and gestational age <26 weeks (IRR: 2.5; 95% CI: 1.7-3.8; P<0.001). The rate of BSI per 1000 patient-days was 40 times higher in infants with both of these than in infants with neither. If validated in other settings, stratification of neonatal BSI rate by two unambiguous risk factors, parenteral nutrition and birth gestational age <26 weeks, offers a simple method to make meaningful intra- and inter-hospital comparisons.

Early switch and early discharge strategies in patients with community-acquired pneumonia: a meta-analysis.

BACKGROUND: The effectiveness of early switch and early discharge strategies in patients with community-acquired pneumonia remains unknown. METHODS: We searched the MEDLINE, HEALTHSTAR, EMBASE, Cochrane Collaboration, and Best Evidence databases from January 1, 1980, to March 31, 2000, for community-acquired pneumonia studies that included specific switch criteria or recommendations to switch on a particular day. RESULTS: From 1794 titles identified, 121 articles were reviewed. We identified 10 prospective, interventional, community-acquired pneumonia-specific studies that evaluated length of stay (LOS). Nine studies applied an early switch from parenteral to oral antibiotic criteria. Six different criteria for switching were applied in the 9 studies. Five of the studies that applied early switch criteria also applied separate criteria for early discharge. Six studies applied an early switch and early discharge strategy to an intervention and control group, and 5 of these provided SD values for LOS. The mean change in LOS was not significantly (P =.05) reduced in studies of early switch and early discharge (-1.64 days; 95% confidence interval, -3.30 to 0.02 days). However, when the 2 studies in which the recommended LOS was longer than the control LOS were excluded from the analysis, the mean change in LOS was reduced by 3 days (-3.04 days; 95% confidence interval, -4.90 to -1.19 days). Studies did not reveal significant differences in clinical outcomes between the intervention and control groups. CONCLUSIONS: There is considerable variability in early switch from parenteral to oral antibiotic criteria for patients with community-acquired pneumonia. Early switch and early discharge strategies may significantly and safely reduce the mean LOS when the recommended LOS is shorter than the actual LOS.

Studies of the presence of verocytotoxic Escherichia coli O157 in bovine faeces submitted for diagnostic purposes in England and Wales and on beef carcases in abattoirs in the United Kingdom.

A survey of beef carcases in abattoirs in the UK was carried out in order to estimate the prevalence of contamination with verocytotoxin-producing Escherichia coli (VTEC) serogroup O157. Contamination with verocytotoxin-producing E. coli (VTEC) O157 was confirmed in 0.47% of the 4067 (95% confidence limits 0.22-1.00%) of neck muscle samples. A significant tendency for carcases present in the same abattoir on the same day to have similar results was found, thus suggesting cross contamination. VTEC O157 was found in 0.83% of 6495 bovine faeces samples routinely submitted for diagnostic purposes to Veterinary Investigation Centres in England and Wales. Of the samples from cattle less than 6 months old, 3.7% of 68 samples from animals without gastrointestinal disease were positive for E. coli O157, in contrast to 0.75% of 2321 samples from cases of gastrointestinal disease. No association with season or herd type (beef or dairy) was found.

Serological prevalence of Hypoderma species in cattle in Great Britain (1995/96) and the relative value of serological surveillance over clinical observation.

Sera from 100,400 cattle on 2850 farms in England, Scotland and Wales were tested for the presence of antibodies to Hypoderma species between the end of November 1995 and the end of February 1996. Twelve animals were resampled because the initial results were equivocal but only one of them was confirmed as seropositive. This animal was a bull imported from Belgium which had been treated with an approved warble fly treatment within 24 hours of arrival at its destination in Great Britain. No seropositive animals were confirmed within the native British cattle population. Statistical analysis of these data indicates that the probable maximum number of infested cattle herds in Great Britain is 112. To detect the disease by direct clinical observation would require more than 500 herds to be infested, indicating that the serological testing of this number of cattle and farms is more than four times as sensitive as clinical observation for the detection of hypodermosis.

An investigation of risk factors for cases of bovine spongiform encephalopathy born after the introduction of the 'feed ban'.

Bovine spongiform encephalopathy (BSE) occurred in cattle in Great Britain after the inclusion of protein derived from infected tissues in their feed, and the incidence of the disease has been reduced by the introduction of legislation to prevent the inclusion of such protein in ruminant feed. This paper describes a case-control study designed to investigate whether there is any evidence for direct transmission of infection to cattle born after the introduction of this legislation. The offspring of animals that were subsequently affected with BSE were not found significantly more often among the cases. There was a statistically significant risk for animals born up to three days after a subsequently affected animal calved, but it may not indicate a causal association. Even after adjusting for an animal's exposure to infected animals that calved but would have been culled from the herd before developing clinical signs of BSE these routes of transmission could not account for the majority of cases born after the introduction of the legislation. A between herd comparison is suggested as a method of investigating alternative sources of infection.

The occurrence of Mycobacterium bovis infection in cattle in and around an area subject to extensive badger (Meles meles) control.

The occurrence of Mycobacterium bovis infection in cattle herds during the period 1966-92 in two geographically related areas in South-West England is compared. In one area comprising 104 km2 all badgers were systematically destroyed from 1975-81, after which recolonization was allowed; in the other, comprising 116 km2, small scale, statutory badger removal operations were undertaken from 1975 onwards where specific herds were detected with M. bovis infection. In the area with total clearance, no further incidents with M. bovis isolation occurred from 1982-92. Survival analysis and proportional hazards regression indicated that the risk of herds being identified with infection was less once badgers had been cleared from their neighbourhood, whereas it was greater in herds with 50 or more animals, and once cattle in a herd had responded positively to the tuberculin skin test, even though infection with M. bovis was not confirmed subsequently. The study provides further evidence that badgers represent an important reservoir of M. bovis infection for cattle and that badger control is effective in reducing incidents of cattle infection with M. bovis if action is thorough and recolonization is prevented.

Breast biopsy rate and positivity in Rhode Island.

Breast biopsy is a common procedure for which few age-specific, population-based data are available. We identified all women who underwent breast biopsy in Rhode Island in 1989 by reviewing the specimen logs at each of 13 pathology laboratories. Among 425,000 women aged 15-97 years, 2685 underwent breast biopsy, for an overall rate of 6/1000. The rate increased with age, peaking among 45- to 54-year-olds and then declining in women over 75. Among those biopsied, 726 were diagnosed with breast cancer, for an overall biopsy positivity of 27%. In contrast to rate, positivity increased steadily with age. These results are within the range of estimates produced by smaller group studies.

Investigation of a staphylococcal food poisoning outbreak in a centralized school lunch program.

The trend in many communities toward centralized school lunch preparation potentially increases the risk of foodborne illness. Foods often are prepared long before serving and may be distributed to satellite schools by persons with little formal training in safe techniques of food preparation or food service. In May 1990, an outbreak of staphylococcal food poisoning occurred in elementary schools in a Rhode Island community participating in such a program. In the investigation of the outbreak, students in schools that reported cases were interviewed. Food preparation, handling, and distribution were reviewed. At School E, 662 lunches were prepared and distributed to 4 additional schools (schools A-D). Schools A and B accounted for nearly all cases of the food poisoning, with rates of 47 percent and 18 percent. Eating ham increased the risk of illness (62 percent of those consuming ham and 3 percent of those who did not, relative risk = 18.0, 95 percent confidence interval = 4.0, 313.4). Large amounts of Staphylococcus aureus were cultured, and preformed enterotoxin A was identified in leftover ham. A food handler, who tested positive for the implicated enterotoxic strain S. aureus, reported having removed the casings from two of nine warm ham rolls 48 hours prior to service. Because of improper refrigeration, prolonged handling, and inadequate reheating, the ham was held at temperatures estimated at 10-49 degrees Celsius (50-120 degrees Fahrenheit) for a minimum of 15 hours. The potential for larger outbreaks prompted a statewide training program in safe food preparation for school lunch personnel, which may have applications for other communities.

Alcohol consumption in men exposed to the military draft lottery: a natural experiment.

The randomized natural experiment provided by the military draft lotteries of 1970, 1971, and 1972 is used to compare alcohol consumption in men born in the years 1950, 1951, and 1952. Alcohol consumption data are derived from the National Health Interview Survey supplements for 1977, 1983, and 1985. The analysis follows an intention-to-draft paradigm, where draft eligibility is determined solely by randomly assigned lottery numbers. Draft eligibility status is found to be unassociated with alcohol consumption, despite the fact that eligibility for the draft significantly increased the likelihood of military service and that veterans are more likely to report increased alcohol consumption compared to nonveterans. The randomized draft lottery provides an elegant natural experiment that potentially obviates the problem of confounding by premilitary service factors found in previous studies of alcohol consumption among veterans and nonveterans. However, the indirect association between draft eligibility and any health outcome (where military service is an intervening variable), together with the failure of the draft to produce a higher percent of veterans, prohibits application in all but the largest samples.

Alcohol consumption and problem drinking in Vietnam era veterans and nonveterans.

The relationship between Vietnam era veteran status and 13 indicators of alcohol consumption and problem drinking is examined using data from the 1977, 1983 and 1985 National Health Interview Surveys conducted by the National Center for Health Statistics. Compared to a group of nonveterans frequency matched on age, a greater proportion of Vietnam era veterans are currently heavy drinkers and a smaller proportion are abstainers, after simultaneous adjustment for seven demographic factors (age, region of the U.S., urbanization, ethnicity, marital status, education and income). Further, both white veterans and white nonveterans demonstrate an effect of increasing abstention with increasing age across the 3 interview years. In all race and veteran groups the proportion of lifetime abstainers can be ranked in increasing order as follows: white veterans, white nonveterans, non-white veterans and non-white nonveterans. This ranking is reversed for lifetime heavy drinking. Nearly half of the white veterans report drinking heavily at some point in their lives. Among both whites and non-whites, a significantly greater proportion of veterans than nonveterans report alcohol-related motor vehicle crashes or violations.

Anchoring errors in clinical-like judgments.

Anchoring errors occur when the final judgment in a series is biased in the direction of the initial judgment. Subjects (142 undergraduates) made sequential judgments about each of four cases (Alcohol Abuse, Anxiety, Depression, Antisocial Behavior). After each of five segments of case material, subjects rated the case's severity and prognosis and their own confidence in these judgments. It was found that initial judgments significantly predicted most of the later judgments, which demonstrated the anchoring effect. The anchoring effect occurred most strongly for the Antisocial and Anxiety cases, moderately for the Alcohol case, and only modestly for the Depression case. Contrary to expectation, confidence was related negatively to the occurrence of the anchoring effect; that is, anchoring was highest when confidence was low. Implications of this study are discussed.

Bovine spongiform encephalopathy: diagnostic significance of vacuolar changes in selected nuclei of the medulla oblongata.

The adequacy of a histopathological diagnosis of bovine spongiform encephalopathy (BSE) based exclusively on observations of neuroparenchymal vacuolation in three specific neuroanatomic nuclei was tested by using a standard coronal section of medulla oblongata cut at the obex. The agreement between the observations and the definitive histopathological diagnosis was assessed in each of 684 bovine brains - 563 confirmed cases of BSE, 20 with changes which did not diagnose BSE conclusively and 101 in which the lesions of BSE were not detected. When the assessment was confined to the solitary tract nucleus and the spinal tract nucleus of the trigeminal nerve a positive result was obtained in 99.6 per cent of confirmed cases of BSE and only 1 per cent of brains in which lesions of BSE were not detected gave a false positive result. Thus an initial examination of the single section, together with an examination of representative areas of the rest of the brain when no unequivocal lesion was found, provided a satisfactory method for the routine diagnosis of BSE.

Alcohol consumption and problem drinking in white male veterans and nonveterans.

The relation between veteran status and 15 indicators of alcohol consumption and problem drinking is examined using data from the 1977, 1983, and 1985 National Health Interview Surveys conducted by the National Center for Health Statistics. After simultaneous adjustment for age, region of the US, urbanization, ethnicity, marital status, education, and income, a greater proportion of White male veterans than White male nonveterans were heavy drinkers and a smaller proportion were abstainers. This association appeared in all three survey years; further, veterans consistently reported a high daily consumption level (the equivalent of approximately six bottles of beer, five glasses of wine, or four mixed drinks) compared to nonveterans. Among White male veterans, 6.9 percent reported family or marital problems and 13.9 percent reported motor vehicle crashes or violations compared to 4.4 percent and 8.9 percent, respectively, among nonveterans. The same pattern was observed for lifetime prevalences of alcoholism (veterans have nearly two and a half times the lifetime prevalence of nonveterans), cirrhosis of the liver, and unspecified alcohol-related problems.

Vital records in the development of injury control research.

Most of the resources of the emergency physician are devoted to persons already injured, with little emphasis on prevention. Analyses of state and local injury statistics are necessary to identify local prevention needs in order to set program priorities. We discuss an example, an analysis of statewide injury fatalities identified through the Illinois Vital Records database. The overall death rate for injuries in illinois was lower than that found for the United States. However, the need for research on several high-risk age groups for certain injuries was identified. Most notably, the homicide rate for those 15 to 24 years old was 140% of the national rate. Other specific nonwhite age groups were overrepresented in poisoning, fire, and firearm deaths, while specific white age groups were overrepresented in suicide, fall, and drowning deaths. The research regarding the etiologies of these injuries and the formulation and evaluation of prevention strategies based on this research must be interdisciplinary. The emergency physician is in a unique position to serve as a member of such an interdisciplinary injury control team, but currently there is little emphasis on or training for this role.

Effect of air filtration on respiratory disease in intensively housed veal calves.

The effect of a recirculating air filter unit on concentrations of airborne bacteria, clinical and subclinical respiratory disease and production performance of veal calves was studied over a period of one year. Six groups of 28 calves in sheds with internally filtered air were paired by age and time of entry with six similar groups in non-filtered sheds; they were also compared with 23 groups, each of 28 calves, in non-filtered sheds present in the unit during the period of study. Mean aerial bacteria concentration in filtered sheds was reduced by 44.9 per cent (P less than 0.0001). A comparison of unfiltered and filtered sheds on a paired basis showed that the number of animals requiring antibiotic treatment for respiratory disease was reduced by 19.3 per cent (P greater than 0.05). The number of repeat courses of treatment was reduced by 28.9 per cent (P less than 0.025) and total antibiotic usage was reduced by 34.8 per cent (P less than 0.025). At slaughter the average area of lung consolidation in calves from filtered sheds was reduced by 38.4 per cent (P less than 0.025. When all the 644 calves in the unit from 23 non-filtered sheds were compared with the 168 calves in the six filtered sheds the reduction in first treatments, repeat courses and total treatments were 19.7 per cent (P less than 0.025), 28.3 per cent (P less than 0.025) and 31.6 per cent (P less than 0.025) respectively. Air filtration was therefore associated with a reduction in both incidence and severity of clinical and subclinical disease in calves. Both treatment for respiratory disease and area of lung consolidation at slaughter were directly related to reductions in daily weight gain. The economic effect of respiratory disease on veal calves is briefly discussed.

A survey of mastitis in the British dairy herd.

Five hundred herds were examined to determine the prevalence of subclinical mastitis in the British dairy herd. The prevalences of the various infections recorded were Streptococcus agalactiae 3.4 per cent of quarters, S dysgalactiae 1.1 per cent, S uberis 1.5 per cent and Staphylococcus pyogenes 8.1 per cent. There were regional differences in the prevalence of some of these pathogens. The national prevalence of subclinical mastitis as defined by the International Dairy Federation was 9.6 per cent of all quarters. Udder infections were less prevalent in herds where mastitis control measures were being used. The prevalence of infection also declined as the size of herd increased. However, as the uptake of mastitis control measures was greater in the larger herds it seems likely that the widespread use of control measures was the most important factor responsible for the relatively low prevalence of subclinical mastitis.

Epidemiological studies of calf respiratory disease in a large commercial veal unit.

Records of treatments for respiratory disease among 952 calves in a large intensive veal unit were analysed. The frequency of disease was heavily age-dependent in the 34 batches of 28 calves with a peak at five weeks of age and little disease before the fourth or after the eighth week. The effect was evident for all of the three indices of disease examined: the numbers of first treatments, numbers of new courses of treatment and the total number of treatments. Transient synchronisation of outbreaks of disease in separate batches was observed but attempts to correlate the level of disease with climatic events, using data from local meteorological stations, were unsuccessful. Disease was shown to be clustered within crops of calves at one end of the housing or the other, indicating that contact spread may have been important. A variation in the amount of disease on each day of the week may have been attributable to restricted feeding on Sundays.