Ascites improves upon [corrected] serum sodium plus [corrected] model for end-stage liver disease (MELD) for predicting mortality in patients with advanced liver disease.

BACKGROUND: The clinical impact of ascites has historically been well recognized; however, its value is unclear in the context of current prognostic models. AIM: To determine whether ascites can improve risk discrimination beyond model for end-stage liver disease (MELD) and serum sodium (MELDNa). METHODS: Consecutive cirrhotic patients were evaluated for ascites on the basis of an outpatient CT along with concurrent MELD and Na values. Cox models were used to determine the added value of ascites for predicting 1-year mortality. Increases in the C-index, integrated discrimination improvement (IDI) and the net reclassification index (NRI) were used to assess improvements in discrimination after the addition of ascites. RESULTS: A total of 1003 patients had Na and MELD scores available within 30 days of the CT scan. A total of 60 deaths occurred within 1 year, with mortality higher in patients with ascites (21.4% vs. 4.0%, HR 6.08, 95% CI 3.62-10.19, P < 0.0005). In the presence of ascites, the MELD and MELDNa scores underestimated mortality risk when the scores were less than 21. The addition of ascites to the MELDNa model substantially improved discrimination by the C-index (0.804 vs. 0.770, increase of 3.4%, 95% CI 0.2-9.9%), IDI (1.8%, P = 0.016) and NRI (15.8%, P = 0.0006). CONCLUSION: The incorporation of radiographic ascites significantly improves upon MELDNa for predicting 1-year mortality. The presence of ascites may help identify patients at increased risk for mortality, not otherwise captured by either MELD or MELDNa.

The effects of executive and behavioral dysfunction on the course of ALS.

OBJECTIVE: To determine whether patients with ALS-frontotemporal lobar dementia (FTLD) have a shorter survival and are less compliant with recommended treatments than those with ALS who have normal executive and behavioral function (classic ALS). METHODS: Survival analysis from ALS symptom onset to death included 81 of 100 consecutive patients who could be classified definitely as ALS with abnormal executive or behavioral function or as classic ALS. Criteria were defined for compliance with noninvasive positive-pressure ventilation (NPPV) and percutaneous endoscopic gastrostomy (PEG). RESULTS: Median survival was 2 years 4 months for the 28 patients with FTLD and 3 years 3 months for the 53 patients with classic ALS (relative hazard for death 1.93, CI 1.09 to 3.43; p = 0.024). However, the relative hazard associated with FTLD (1.49) in the multivariate model was diminished by the association of FTLD with bulbar onset and older age and was not significant in this sample size. With bulbar onset, median survival was 2 years 0 months for the 14 with ALS-FTLD and 2 years 10 months for the 10 with classic ALS (relative hazard for death 2.78, CI 1.02 to 7.55; p = 0.045), and older age was not a significant risk. Noncompliance with NPPV and PEG were 75% and 72% in ALS-FTLD, respectively, vs 38% and 31% in classic ALS (relative risks 2.00 and 2.34; p = 0.013 and 0.022). CONCLUSIONS: Survival is significantly shorter among patients with ALS-FTLD than with classic ALS. Furthermore, patients with ALS-FTLD are twice as likely to be noncompliant.

Emergency health surveillance after severe flooding in Louisiana, 1995.

INTRODUCTION: In disaster situations, timely surveillance systems that provide illness, injury, and mortality information to public health officials and hospitals are essential for planning and evaluating interventions. OBJECTIVES: To describe flood surveillance methodology, the impact of the event on hospitals, and the number of daily patient visits due to selected illnesses and injuries before, during, and after severe flooding in southeastern Louisiana in May 1995. METHODS: Survey of disaster-area hospitals regarding flood impact. Emergency department surveillance of injuries and illnesses for the week before, the two days during, and the week after the flood. RESULTS: There occurred an increase in the number of persons who drowned or were injured that presented to the moderately affected hospitals during the storm, but there was no increase in visits for gastroenteritis to any group of hospitals. Services were disrupted in more than half of hospitals. The severely affected hospitals had the least variation in the average number of daily visits. None of the drownings were reported by those hospitals that reported severe service disruption. CONCLUSIONS: Data should be collected from all hospitals in or near disaster areas, even if they were not directly affected by the disaster. Public education about the danger of drowning during flash flooding must be improved. The Louisiana experience emphasizes the need for a disaster-preparedness plan for rapid surveillance of illnesses and injuries.

What white blood cell count should prompt antibiotic treatment in a febrile child? Tutorial on the importance of disease likelihood to the interpretation of diagnostic tests.

Most diagnostic tests are not dichotomous (negative or positive) but, rather, have a range of possible results (very negative to very positive). If the pretest probability of disease is high, the test result that prompts treatment should be any value that is even mildly positive. If the pretest probability of disease is low, the test result needed to justify treatment should be very positive. Simple decision rules that fix the cutpoint separating positive from negative test results do not take into account the individual patient's pretest probability of disease. Allowing the cutpoint to change with the pretest probability of disease increases the value of the test. This is primarily an issue when the pretest probability of disease varies widely between patients and depends on characteristics that are not measured by the test. It remains an issue for decision rules based on multiple test results if these rules fail to account for important determinants of patient-specific risk. This tutorial demonstrates how the value of a diagnostic test depends on the ability to vary the cutpoint, using as an example the white blood cell count in febrile children at risk for bacteremia.

Optimal gestational age and birth-weight cutoffs to predict neonatal morbidity.

BACKGROUND: Gestational age (GA) and birth weight (BW) criteria are used to identify newborns at risk for neonatal morbidity. Currently, preterm is GA less than 37 weeks; low birth weight is BW less than 2,500 grams; and small for gestational age (SGA) is BW less than the tenth percentile weight for the infant's GA. The optimal classification system balances the misclassification cost of false negatives against the cost of false positives. OBJECTIVE: To calculate the relative misclassification costs implied by the current 37-week and 2,500-gram cutoffs, and to test the validity of the current definition of SGA as a predictor of term morbidities. METHODS: GA, BW, and morbidity information were collected for 22,606 infants born between July 1981 and December 1992. Using this dataset, logistic regression coefficients were obtained modeling GA or BW as predictors of morbidities associated with prematurity. For a subset of 18,813 infants with GAs between 37 and 41 weeks, coefficients were obtained modeling both GA and BW as independent predictors of term morbidities. The logistic regression coefficients were used to calculate optimal birth weight, gestational age, and birth-weight-for-gestational-age cutoffs. RESULTS: The current definitions of low birth weight and preterm imply that it is 18 to 28 times more costly to misclassify a sick infant as low-risk than to misclassify a well infant as high-risk. CONCLUSIONS: Gestational age alone is better than birth weight alone at predicting preterm morbidities. No birth-weight cutoff can adequately predict term morbidities. A single weight-percentile cutoff for all gestational ages should not be used to identify newborns at high risk for neonatal morbidity.

Epidemiologic analysis of an urban, public emergency department's frequent users.

OBJECTIVES: To determine how the demographic, clinical, and utilization characteristics of emergency department (ED) frequent users differ from those of other ED patients. METHODS: A cross-sectional and retrospective cohort study was performed using a database of all 348,858 visits to the San Francisco General Hospital ED during a five-year period (July 1, 1993, to June 30, 1998). A "frequent user" visited the ED five or more times in a 12-month period. RESULTS: Frequent users constituted 3.9% of ED patients but accounted for 20.5% of ED visits. The relative risk (RR) of frequent use was high among patients who were homeless (RR = 4.5), African American (RR = 1.8), and Medi-Cal sponsored (RR = 2.1). Frequent users were more likely to be seen for alcohol withdrawal (RR = 4.4), alcohol dependence (RR = 3.4), and alcohol intoxication (RR = 2.4). Frequent users were also more likely to visit for exacerbations of chronic conditions, including sickle cell anemia (RR = 8.0), renal failure (RR = 3.6), and chronic obstructive pulmonary disease (RR = 3.3). They were less likely to visit for all forms of trauma (RR = 0.43). Survival analysis showed that only 38% of frequent users for one year remained frequent users the next year. However, 56% of frequent users for two consecutive years remained frequent users in the third year. CONCLUSIONS: Frequent use of the ED reflects the urban social problems of homelessness, poverty, alcohol abuse, and chronic illness. Frequent use of the ED shows a high rate of decline from one year to the next. This rate of decline slows after the first year and suggests the existence of a smaller group of chronic frequent users.

Multi-state outbreaks of acute gastroenteritis traced to fecal-contaminated oysters harvested in Louisiana.

Norwalk-like viruses (NLVs), or small round structured viruses, are known to cause acute gastroenteritis associated with eating contaminated shellfish. Between 1993 and 1996, three oyster-related gastroenteritis outbreaks attributed to NLV occurred in Louisiana. Intensive trace-back and environmental investigations revealed that the overboard disposal of sewage by oyster harvesters into oyster-bed waters was the most likely source of contamination in at least two of the outbreaks. The small infectious dose of NLV, the large quantity of virus particles in stool, and the ability of oysters to concentrate virus particles suggest that oyster-related outbreaks will continue unless strong control measures are established. Efforts to halt improper sewage disposal in oyster-harvesting waters, including overboard sewage discharge, must be undertaken if future outbreaks are to be prevented.

Acute effects of nitrogen dioxide after accidental release.

OBJECTIVES: Following an accidental release of nitrogen dioxide from a railroad tank car containing nitrous tetroxide, the authors undertook a study of the health effects of the release, measuring the association between acute low level exposure and pulmonary symptoms. METHODS: The authors reviewed the records of three emergency departments, surveyed 80 emergency department patients, 552 community residents, 21 chemical plant workers, and 29 emergency workers, and conducted a case-control study. Pulmonary case status was defined as having an objective pulmonary finding noted on the emergency department record, reporting that the onset of symptoms was subsequent to the release, and being within the city limits at the time of the release. Self-reported case status was defined as reporting one or more symptoms consistent with exposure to nitrogen dioxide in the week after the release and having been within the city limits at the time of the release. Control subjects were survey respondents who reported no symptoms in the week after the release and had been within the city limits at the time of the release. Chemical exposure was characterized by proximity to, direction from, and being outdoors within one hour after the release. Duration of potential exposure was not measured. Logistic regression was used to estimate odds ratios and 95% confidence interval for symptoms by exposure level, adjusted for age, sex, smoking, and preexisting pulmonary conditions. RESULTS: Local emergency department visits increased fivefold in the week after the release. The most common complaints recorded in a systematic sample of 528 visits in the first 30 hours after the release were headache (31%), burning eyes (30%), and sore throat (24%). Objective pulmonary findings were recorded for 41 (5%) patients in the week before and 165 (4%) in the week after the release. The odds of being a pulmonary case increased by 40% for each quarter-mile increment in proximity to the release (odds ratio [OR] 1.4; 95% confidence interval [CI] 1.1, 1.7), while the odds of being a self-reported case increased by 20% for each quarter-mile increment in proximity (OR 1.2, 95% CI 1.1, 1.4). People who met the pulmonary case definition were 2.5 times (CI 1.3, 4.8) more likely than control subjects to have been outdoors and 6.4 times (CI 3.2, 12.6) more likely to report a preexisting pulmonary condition. Self-reported cases were 2.6 times (95% CI 1.8, 3.8) more likely than control subjects to have been outdoors and 1.9 times (95% CI 1.1, 3.1) more likely to report a preexisting pulmonary condition. CONCLUSIONS: Emergency department visits increased five-fold, but serious acute health effects were uncommon. People who met the pulmonary case definition were six times more likely to report pulmonary symptoms than those without preexisting conditions. This study was not designed to determine any potential long-term effects of exposure.

The need for more aggressive follow-up of children born to hepatitis B surface antigen-positive mothers: lessons from the Louisiana Perinatal Hepatitis B Immunization Program.

BACKGROUND: Preventing perinatal transmission of hepatitis B virus (HBV) is an important part of strategies to prevent HBV-related disease. To help prevent perinatal transmission the Louisiana Office of Public Health began in 1990 a statewide program to track children of hepatitis B surface antigen (HBsAg)-positive mothers. We examined data from this program to evaluate the effectiveness of the program and to assess the value of serologic testing in the program. METHODS: We examined vaccination and testing records for all children listed in the program database who were old enough to have been tested, according to program recommendations, as of July, 1993. RESULTS: Of 426 children 269 (63%) had been completely vaccinated. Also of these 426 children 194 (46%) were tested for hepatitis B surface antibody (anti-HBs) and 163 (38%) were tested for HBsAg. Among tested children 6 (4%) were HBsAg-positive and 22 (11%) were anti-HBs-negative. Incompletely vaccinated children were more likely than completely vaccinated children to be HBsAg-positive (risk ratio, 7.9; 95% confidence interval, 1.5 to 41.2) and less likely to be positive for anti-HBs (risk ratio, 0.5, confidence interval, 0.3 to 0.7). Children tested > or = 18 months after the last vaccine dose were more likely than children tested earlier to be anti-HBs-negative (risk ratio, 0.8; 95% confidence interval, 0.7 to 1.1). CONCLUSIONS: Rates of vaccination completion and postvaccination serologic testing were low for children in this program. Even with these low vaccination rates, however, we estimate that the program prevented 74% of HBV infection and 87% of HBV carriage in this group of high risk children, suggesting that failure to vaccinate rather than vaccine failure was the major obstacle to prevention of perinatal HBV transmission. Serologic testing was useful in that it identified children with chronic HBV infection and children who may have needed additional doses of vaccine, but it should be performed < 18 months after the last dose of vaccine is given. More aggressive follow-up of these children for both vaccination and serologic testing is needed.

Spinal cord injuries in Louisiana due to falls from deer stands, 1985-1994.

Serious injuries resulting in paralysis and death have occurred to hunters who have fallen from deer stands that were not equipped with safety restraints. Among the most serious of these are spinal cord injuries. We examined all deer stand-related spinal cord injuries reported to Louisiana's Spinal Cord Injuries Registry from 1985 through 1994. During the 1985 through 1991 hunting seasons, we received reports of 28 deer stand falls resulting in permanent paralysis (an average of four each year) and 13 reports of temporary neurologic deficit. These injuries led to first-year medical care charges estimated at more than $4.2 million. None of the patients in the reported cases were using a safety restraint at the time of injury. After a public information campaign to make hunters aware of the risk of using deer stands without safety belts was conducted in 1992, there were no reported spinal cord injuries associated with deer stand falls for the following three years.

Heat exposure in an enclosed automobile.

During July 1995, an infant in southeast Louisiana died as a result of heat exposure in an enclosed automobile. To evaluate degree of heat exposure in a vehicle, we compared the temperature rise inside an enclosed, dark-colored vehicle with the temperature rise in light-colored vehicle with the windows partly open. Within 20 minutes, readings in both cars exceeded 125 degrees F and reached approximately 140 degrees F in 40 minutes--a temperature rise of over 45 degrees F. A person who is unable to remove himself from an enclosed vehicle is at risk for a life-threatening crisis if left alone in a sun-exposed car for even a relatively short period of time.

Epidemiologic applications of novel molecular methods to detect and differentiate small round structured viruses (Norwalk-like viruses).

The molecular epidemiology of a large, multistate outbreak of oyster-associated gastroenteritis [Kohn et al. (1995): Journal of the American Medical Association 273:466-471. Dowell et al. (1995): Journal of Infectious Diseases 171:1497-1503.] was examined using new methods to detect small round structured viruses (SRSVs) by reverse transcription-polymerase chain reaction (RT-PCR) and to characterize strains by Southern hybridization and nucleotide sequencing of 81-bp of a PCR product amplified from the RNA polymerase gene. Of 37 stool specimens examined from patients in eight clusters of the multistate outbreak, 32 (86%) gave RT-PCR products specific for SRSVs of P1-A phylogenetic group. Nineteen PCR products from the eight clusters were confirmed to have the identical sequence, indicating that this large outbreak was attributed to a single strain of SRSV. In one of the eight clusters, five (63%) of eight patients had a mixed infection with a second SRSV strain that belonged to P2-B phylogenetic group. Of 12 specimens from patients in five other outbreaks and one sporadic case which occurred at the same time as the multistate outbreak, 10 (83%) gave products specific for SRSVs representing four phylogenetic groups (P1-A, P1-B, P2-A, and P2-B). The sequences of the P1-A products from two outbreaks and that of the P2-B product from another outbreak were identical to the P1-A sequence from the eight clusters and the P2-B sequence from the one cluster of the multistate outbreak, respectively. These results demonstrate the first application of these methods to enhance our understanding of the molecular epidemiology of SRSVs and provide answers of public health interest that could not have been obtained using classical epidemiologic methods alone.

Fatal illness associated with a new hantavirus in Louisiana.

A fatal case of hantaviral illness occurred in Louisiana, outside of the range of P. maniculatus, the rodent reservoir for Sin Nombre virus. Hantavirus RNA and antigens were detected in patient autopsy tissues, and nucleotide sequence analysis of amplified polymerase chain reaction (PCR) products identified a newly recognized unique hantavirus, provisionally named Bayou virus. Prominent features of the clinical illness are compatible with hantavirus pulmonary syndrome (HPS), but several features such as renal insufficiency and intraalveolar hemorrhage are more compatible with hemorrhagic fever with renal syndrome (HFRS), a disease associated with Eurasian hantaviruses.

Three summertime outbreaks of influenza type A.

In the Northern Hemisphere, sporadic cases of influenza occur during the summer, yet summertime outbreaks are rare. From 12 August through 2 September 1993, three influenza outbreaks in Louisiana were investigated using medical-record review, interviews, viral cultures, serology, and active surveillance for influenza-like illness in Louisiana. Attack rates in the outbreaks were 61% (69/114), 42% (24/57), and 45% (23/51). Viruses isolated were most closely related to influenza A/Beijing/32/92 (H3N2). The identification of influenza A as the cause of the first two outbreaks led to the recommendation for amantadine use in the third outbreak. Active surveillance did not detect any other outbreaks of influenza-like illness during August or September 1993. Out-of-season influenza A outbreaks can therefore occur when little influenza-like illness is present in a community. Evaluation of outbreaks of acute, febrile respiratory illness outside the influenza season should include this possibility, since rapid detection can lead to the timely use of amantadine or rimantadine.

An outbreak of Norwalk virus gastroenteritis associated with eating raw oysters. Implications for maintaining safe oyster beds.

OBJECTIVE: To determine the characteristics and the cause of an outbreak of gastroenteritis associated with eating raw oysters. DESIGN: Survey of groups of persons reporting illness to the health department after eating oysters; survey of convenience sample of oyster harvesters; and tracing of implicated oysters. SETTING: General community. MAIN OUTCOME MEASURES: Relative risk for illness after oyster consumption, source bed of contaminated oysters, presence of antibodies to Norwalk virus in serum, presence of a Norwalk virus in stool by direct electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR), and DNA sequences of RT-PCR products. RESULTS: Seventy (83%) of 84 persons who ate raw oysters became ill vs three (7%) of 43 people who did not eat raw oysters (relative risk, 11.9; 95% confidence interval, 4.0 to 34.2). Eleven (79%) of 14 serum pairs had at least a fourfold increase in antibody to Norwalk virus. All 12 stool samples tested were positive by electron microscopy and/or RT-PCR for Norwalk virus. The RT-PCR products from all seven stool samples tested had identical DNA sequences. Implicated oysters were harvested November 9 through 13, 1993, from a remote oyster bed. Crews from 22 (85%) of 26 oyster harvesting boats working in this area reported routine overboard disposal of sewage. One harvester with a high level of antibodies to Norwalk virus reported having gastroenteritis November 7 through 10 and overboard disposal of feces into the oyster bed. CONCLUSIONS: This outbreak was caused by contamination of oysters in the oyster bed, probably by stool from one or more ill harvesters. Education of oyster harvesters and enforcement of regulations governing waste disposal by oyster harvesting boats might prevent similar outbreaks.