Cohort study of the mortality among patients in New York City with tuberculosis and COVID-19, March 2020 to June 2022

Both tuberculosis (TB) and COVID-19 can affect the respiratory system, and early findings suggest co-occurrence of these infectious diseases can result in elevated mortality. A retrospective cohort of patients who were diagnosed with TB and COVID-19 concurrently (within 120 days) between March 2020 and June 2022 in New York City (NYC) was identified. This cohort was compared with a cohort of patients diagnosed with TB-alone during the same period in terms of demographic information, clinical characteristics, and mortality. Cox proportional hazards regression was used to compare mortality between patient cohorts. One hundred and six patients with concurrent TB/COVID-19 were identified and compared with 902 patients with TB-alone. These two cohorts of patients were largely demographically and clinically similar. However, mortality was higher among patients with concurrent TB/COVID-19 in comparison to patients with TB-alone, even after controlling for age and sex (hazard ratio 2.62, 95% Confidence Interval 1.66-4.13). Nearly one in three (22/70, 31%) patients with concurrent TB/COVID-19 aged 45 and above died during the study period. These results suggest that TB patients with concurrent COVID-19 were at high risk for mortality. It is important that, as a high-risk group, patients with TB are prioritized for resources to quickly diagnose and treat COVID-19, and provided with tools and information to protect themselves from COVID-19.

COVID-19 Case Investigation and Contact Tracing in New York City, June 1, 2020, to October 31, 2021

IMPORTANCE

Contact tracing is a core strategy for preventing the spread of many infectious diseases of public health concern. Better understanding of the outcomes of contact tracing for COVID-19 as well as the operational opportunities and challenges in establishing a program for a jurisdiction as large as New York City (NYC) is important for the evaluation of this strategy.

OBJECTIVE

To describe the establishment, scaling, and maintenance of Trace, NYC's contact tracing program, and share data on outcomes during its first 17 months.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included people with laboratory test-confirmed and probable COVID-19 and their contacts in NYC between June 1, 2020, and October 31, 2021. Trace launched on June 1, 2020, and had a workforce of 4147 contact tracers, with the majority of the workforce performing their jobs completely remotely. Data were analyzed in March 2022.

MAIN OUTCOMES AND MEASURES

Number and proportion of persons with COVID-19 and contacts on whom investigations were attempted and completed; timeliness of interviews relative to symptom onset or exposure for symptomatic cases and contacts, respectively.

RESULTS

Case investigations were attempted for 941 035 persons. Of those, 840 922 (89.4%) were reached and 711 353 (75.6%) completed an intake interview (women and girls, 358 775 [50.4%]; 60 178 [8.5%] Asian, 110 636 [15.6%] Black, 210 489 [28.3%] Hispanic or Latino, 157 349 [22.1%] White). Interviews were attempted for 1 218 650 contacts. Of those, 904 927 (74.3%) were reached, and 590 333 (48.4%) completed intake (women and girls, 219 261 [37.2%]; 47 403 [8.0%] Asian, 98 916 [16.8%] Black, 177 600 [30.1%] Hispanic or Latino, 116 559 [19.7%] White). Completion rates were consistent over time and resistant to changes related to vaccination as well as isolation and quarantine guidance. Among symptomatic cases, median time from symptom onset to intake completion was 4.7 days; a median 1.4 contacts were identified per case. Median time from contacts' last date of exposure to intake completion was 2.3 days. Among contacts, 30.1% were tested within 14 days of notification. Among cases, 27.8% were known to Trace as contacts. The overall expense for Trace from May 6, 2020, through October 31, 2021, was approximately $600 million.

CONCLUSIONS AND RELEVANCE

Despite the complexity of developing a contact tracing program in a diverse city with a population of over 8 million people, in this case study we were able to identify 1.4 contacts per case and offer resources to safely isolate and quarantine to over 1 million cases and contacts in this study period.

Factors Associated With Sputum Culture-Negative vs Culture-Positive Diagnosis of Pulmonary Tuberculosis

IMPORTANCE

Recognition of active tuberculosis (TB) in its earliest stages could reduce morbidity and prevent advancement to transmissible disease. Little is published about the occurrence and presentation of sputum culture-negative pulmonary TB (PTB), an early paucibacillary but often underrecognized disease state.

OBJECTIVE

To assess differences between culture-negative and culture-positive PTB regarding occurrence, clinical presentation, radiographic findings, demographics, and comorbidities.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study in which surveillance data of adult patients with PTB reported to the New York City Department of Health in New York, New York, from 2011 through 2013, ie, years for which demographic, clinical, and radiographic data were collected. Patients were aged 18 years or older, had signs of pulmonary disease, and had mycobacterial sputum culture results; those with HIV coinfection or a TB diagnosis within 2 years prior to presentation were excluded. Culture-negative PTB was defined as clinical and radiographic presentation consistent with TB, 3 negative results on sputum culture, and improvement with antituberculous treatment. The analyses were performed between 2015 and 2016; notably, the proportion of reported patients with culture-negative PTB has remained consistent during the past 2 decades.

MAIN OUTCOMES AND MEASURES

The occurrence of culture-negative PTB among all patients with PTB was calculated, and demographics, comorbidities, symptoms, and radiographic findings were compared between culture-negative and culture-positive PTB.

RESULTS

Of the 796 patients with PTB (median [interquartile range] age, 41 [29-54] years; 499 [63%] men) who met criteria for analysis, 116 (15%) had negative results on sputum culture. Patients with culture-negative PTB compared with culture-positive PTB were less frequently male (53% vs 64%; P = .03) and presented with a significantly lower frequency of cough (68% vs 89%; P < .001), weight loss (39% vs 51%; P = .03), and cavitation on both chest radiograph (7% vs 28%; P < .001) and chest computed tomographic scan (26% vs 59%; P < .001).

CONCLUSIONS AND RELEVANCE

Given the lack of criterion-standard test confirmation and the relative paucity of symptoms and radiological abnormalities, culture-negative PTB is likely underdiagnosed and its occurrence underestimated globally. Awareness of these findings, enhanced diagnostic approaches, and, ideally, better biomarkers could improve detection and treatment of this early disease and reduce the development of transmissible TB.

758. Tuberculosis Recurrence in New York City: A Retrospective Study

Background

Tuberculosis (TB) recurrence has been difficult to determine due to diverse definitions. Without knowledge of recurrence rates or associated risk factors, patients with highest likelihood of recurrence may not be identified, contributing to continued morbidity and disease transmission. We aimed to determine the recurrence rate for TB cases, associated clinical findings and patient characteristics.

Methods

We conducted a retrospective study evaluating 7,755 New York City TB cases from 2005 to 2014 for recurrence after appropriate treatment completion through 2017. Demographic, clinical, drug susceptibility testing (DST), and genotype data were collected during routine care. Adjusted odds ratios (aOR) were calculated to estimate associated risk factors for recurrence.

Results

A total of 73 cases were identified with ≥ one recurrence, a rate of 0.9%. Median time to recurrence after treatment was 516 days (IQR 165–1,256). In univariate analysis, pulmonary or combination of pulmonary and extrapulmonary disease, human immunodeficiency virus (HIV) infection, culture positive disease, alcohol abuse, intravenous drug use, and homelessness in the 12 months prior to diagnosis were associated with recurrence (P < 0.05). In adjusted analysis, HIV infection (aOR 2.04 95% CI 1.13–3.67), pulmonary disease (aOR 9.03 95% CI 2.19–37.12), and having both pulmonary and extrapulmonary disease (aOR 17.19 95% CI 4.0–74.0) were independently associated with recurrence. Of 67 cases with positive culture and DST, 10 had additional drug resistance and 14 had new disease sites. Among 36 cases with complete genotyping information, data suggested relapse in 27 (75%) cases and re-infection in two (5.5%). Re-infection could not be ruled out in seven (19%) cases.

Conclusion

The recurrence rate for this period was lower than expected compared with other studies. HIV infection continues to be associated with recurrence despite availability of effective antiviral medication. Those with pulmonary or disseminated TB were more likely to have recurrence compared with only extrapulmonary TB. A notable number of recurrent cases demonstrated new drug resistance or disease manifestations, which should be considered in later treatment regimens and follow-up evaluation.

Disclosures

All authors: No reported disclosures.

Treatment correlates of successful outcomes in pulmonary multidrug-resistant tuberculosis: an individual patient data meta-analysis

BACKGROUND

Treatment outcomes for multidrug-resistant tuberculosis remain poor. We aimed to estimate the association of treatment success and death with the use of individual drugs, and the optimal number and duration of treatment with those drugs in patients with multidrug-resistant tuberculosis.

METHODS

In this individual patient data meta-analysis, we searched MEDLINE, Embase, and the Cochrane Library to identify potentially eligible observational and experimental studies published between Jan 1, 2009, and April 30, 2016. We also searched reference lists from all systematic reviews of treatment of multidrug-resistant tuberculosis published since 2009. To be eligible, studies had to report original results, with end of treatment outcomes (treatment completion [success], failure, or relapse) in cohorts of at least 25 adults (aged >18 years). We used anonymised individual patient data from eligible studies, provided by study investigators, regarding clinical characteristics, treatment, and outcomes. Using propensity score-matched generalised mixed effects logistic, or linear regression, we calculated adjusted odds ratios and adjusted risk differences for success or death during treatment, for specific drugs currently used to treat multidrug-resistant tuberculosis, as well as the number of drugs used and treatment duration.

FINDINGS

Of 12 030 patients from 25 countries in 50 studies, 7346 (61%) had treatment success, 1017 (8%) had failure or relapse, and 1729 (14%) died. Compared with failure or relapse, treatment success was positively associated with the use of linezolid (adjusted risk difference 0·15, 95% CI 0·11 to 0·18), levofloxacin (0·15, 0·13 to 0·18), carbapenems (0·14, 0·06 to 0·21), moxifloxacin (0·11, 0·08 to 0·14), bedaquiline (0·10, 0·05 to 0·14), and clofazimine (0·06, 0·01 to 0·10). There was a significant association between reduced mortality and use of linezolid (-0·20, -0·23 to -0·16), levofloxacin (-0·06, -0·09 to -0·04), moxifloxacin (-0·07, -0·10 to -0·04), or bedaquiline (-0·14, -0·19 to -0·10). Compared with regimens without any injectable drug, amikacin provided modest benefits, but kanamycin and capreomycin were associated with worse outcomes. The remaining drugs were associated with slight or no improvements in outcomes. Treatment outcomes were significantly worse for most drugs if they were used despite in-vitro resistance. The optimal number of effective drugs seemed to be five in the initial phase, and four in the continuation phase. In these adjusted analyses, heterogeneity, based on a simulated I² method, was high for approximately half the estimates for specific drugs, although relatively low for number of drugs and durations analyses.

INTERPRETATION

Although inferences are limited by the observational nature of these data, treatment outcomes were significantly better with use of linezolid, later generation fluoroquinolones, bedaquiline, clofazimine, and carbapenems for treatment of multidrug-resistant tuberculosis. These findings emphasise the need for trials to ascertain the optimal combination and duration of these drugs for treatment of this condition.

FUNDING

American Thoracic Society, Canadian Institutes of Health Research, US Centers for Disease Control and Prevention, European Respiratory Society, Infectious Diseases Society of America.

Using Reports of Latent Tuberculosis Infection Among Young Children to Identify Tuberculosis Transmission in New York City, 2006-2012

The presence of latent tuberculosis infection (LTBI) in young children indicates recent tuberculosis (TB) transmission. We reviewed surveillance reports of children with LTBI to assess whether more follow-up is needed to prevent TB in this high-risk population. Data on all children under 5 years of age who were reported by health-care providers or laboratories to the New York City Department of Health during 2006-2012 were abstracted from the TB surveillance and case management system, and those with LTBI were identified. Potential source cases, defined as any infectious TB case diagnosed in the 2 years before a child was reported and whose residence was within 0.5 miles (0.8 km) of the child's residence, were identified. Neighborhood risk factors for TB transmission were examined. Among 3,511 reports of children under age 5 years, 1,722 (49%) had LTBI. The children were aged 2.9 years, on average, and most (64%) had been born in the United States. A potential source case was identified for 92% of the children; 27 children lived in the same building as a TB patient. Children with potential source cases were more likely to reside in neighborhoods with high TB incidence, poverty, and population density. The high proportion of children born in the United States and the young average age of the cases imply that undetected TB transmission occurred. Monitoring reports could be used to identify places where transmission occurred, and additional investigation is needed to prevent TB disease.

Epidemiology of Pediatric Multidrug-Resistant Tuberculosis in the United States, 1993-2014

Background

Multidrug-resistant tuberculosis (MDR-TB) is an important global public health threat, but accurate estimates of MDR-TB burden among children are lacking.

Methods

We analyzed demographic, clinical, and laboratory data for newly diagnosed pediatric (age <15 years) TB cases reported to the US National TB Surveillance System during 1993-2014. MDR-TB was defined as culture-confirmed TB disease with resistance to at least isoniazid and rifampicin. To ascertain potential underestimation of pediatric MDR-TB, we surveyed high-burden states for clinically diagnosed cases treated for MDR-TB.

Results

Of 20789 pediatric TB cases, 5162 (24.8%) had bacteriologically confirmed TB. Among 4826 (93.5%) with drug susceptibility testing, 82 (1.7%) had MDR-TB. Most pediatric MDR-TB cases were female (n = 51 [62%]), median age was 5 years (interquartile range, 1-12 years), one-third were Hispanic (n = 28 [34%]), and two-thirds (n = 55 [67%]) were born in the United States. Most cases had additional resistance to ≥1 other first-line drug (n = 66 [81%]) and one-third had resistance to ≥1 second-line drug (24/73 tested). Of 77 who started treatment prior to 2013, 66 (86%) completed treatment and 4 (5%) died. Among the 4 high-TB-burden states/jurisdictions surveyed, there was 42%-55% underestimation of pediatric MDR-TB cases when using only culture-confirmed case definitions.

Conclusions

Only one-quarter of pediatric TB cases had culture-confirmed TB, likely resulting in underestimation of true pediatric MDR-TB burden in the United States using strictly bacteriologic criteria. Better estimates of pediatric MDR-TB burden in the United States are needed and should include clinical diagnoses based on epidemiologic criteria.

Errors in isolation of patients with infectious tuberculosis at a public teaching hospital in New York

BACKGROUND

Studies report variability in the rates and causes of isolation errors among in-patients with active tuberculosis (TB). We reviewed our experience with delays or premature discontinuation of airborne infection isolation (AII).

METHODS

Medical records of patients admitted to the Bellevue Hospital Center, New York City Health & Hospitals, New York, NY, USA, between January 2006 and July 2012 with a positive respiratory culture for Mycobacterium tuberculosis were reviewed. Patients who were out of AII despite being infectious were identified, as the episodes had prompted a contact investigation.

RESULTS

Of 246 admissions with positive respiratory cultures, 35 AII errors were identified among 27 patients. Most patients had signs or symptoms of TB on admission. Only four patients had positive sputum smears. In 16 (46%) episodes, the patients had never been isolated, 11 (31%) had delayed isolation, and 8 (23%) were prematurely taken off AII. The most common reasons for patients being off AII while infectious were an incorrect alternative diagnosis (15/35, 43%) or a dual diagnosis (9/35, 26%).

CONCLUSIONS

Particularly in smear-negative cases, AII errors due to TB may occur when providers conclude that another diagnosis explains their findings. In many cases, that diagnosis is correct, but TB is also present. This error rate might be a useful quality indicator.

Reportable Bacterial Infections among New York City-Born Infants, 2001-2009

OBJECTIVE

To determine rates of reportable bacterial infections among infants in New York City and identify populations at risk and preventable causes of morbidity.

STUDY DESIGN

This retrospective cohort study matched live births in New York City from 2001-2009 to reported cases of bacterial infections among infants less than 1 year of age. Characteristics recorded on birth certificates were compared between infants with bacterial enteric infection, bacterial nonenteric infection, and no reportable bacterial infection. Multinomial logistic regression and multivariable logistic regression were used to identify risk factors for infection.

RESULTS

Bacterial infection was reported in 4.6 cases per 1000 live births. Of 4524 infants with a reportable infection, the majority (2880, 63%) had an enteric infection. Asian/Pacific Islanders in Brooklyn were the borough-level race/ethnic group with the highest enteric infection rate (8.5 per 1000 live births). Citywide, infants with enteric infections were disproportionately male, from higher poverty neighborhoods, born to foreign-born mothers, and enrolled in Special Supplemental Food Program for Women, Infants, and Children or Medicaid. In contrast, infants with nonenteric infections were more likely to have low birthweight and mothers characterized by US birth and black race or white Hispanic race/ethnicity.

CONCLUSIONS

Distinct patterns of risk factors for enteric and nonenteric bacterial infections among infants were identified. The results suggest that infants born to Asian/Pacific Islander mothers residing in Brooklyn should be a focus of enteric disease prevention. More research is necessary to better understand what behaviors increase the risk of enteric disease in this population.

Moxifloxacin Prophylaxis against MDR TB, New York, New York, USA

Contacts of persons infected with multidrug-resistant tuberculosis (MDR TB) have few prophylaxis options. Of 50 contacts of HIV- and MDR TB–positive persons who were treated with moxifloxacin, 30 completed treatment and 3 discontinued treatment because of gastrointestinal symptoms. Moxifloxacin was generally well-tolerated; further research of its efficacy against MDR TB is needed.

Risk for Tuberculosis Disease Among Contacts with Prior Positive Tuberculin Skin Test: A retrospective Cohort Study, New York City

BACKGROUND

Patients with prior positive tuberculin skin test (TST) results may benefit from prophylaxis after repeat exposure to infectious tuberculosis (TB).

OBJECTIVE

To evaluate factors associated with active TB disease among persons with prior positive TST results named as contacts of persons with infectious TB.

DESIGN

Population-based retrospective cohort study.

PARTICIPANTS

A total of 2,933 contacts with prior positive TST results recently exposed to infectious TB identified in New York City's TB registry during the period from January 1, 1997 through December 31, 2003.

MAIN MEASUREMENTS

Contacts developing active TB disease ≤ 4 years after exposure were identified and compared with those who did not, using Poisson regression analysis. Genotyping was performed on selected Mycobacterium tuberculosis-positive isolates.

KEY RESULTS

Among contacts with prior positive TST results, 39 (1.3 %) developed active TB disease ≤ 4 years after exposure (≤ 2 years: 34). Risk factors for contacts that were independently associated with TB were age < 5 years (adjusted prevalence ratio [aPR] = 19.48; 95 % confidence interval [CI] = 7.15-53.09), household exposure (aPR = 2.60;CI = 1.30-5.21), exposure to infectious patients (i.e., cavities on chest radiograph, acid-fast bacilli on sputum smear; aPR = 1.9 3; CI = 1.01-3.71), and exposure to a U.S.-born index patient (aPR = 4.04; CI = 1.95-8.38). Receipt of more than 1 month of treatment for latent TB infection following the current contact investigation was found to be protective (aPR = 0.27; CI =  .08-0.93). Genotype results were concordant with the index patients among 14 of 15 contacts who developed active TB disease and had genotyping results available.

CONCLUSIONS

Concordant genotype results and a high proportion of contacts developing active TB disease within 2 years of exposure indicate that those with prior positive TST results likely developed active TB disease from recent rather than remote infection. Healthcare providers should consider prophylaxis for contacts with prior TB infection, especially young children and close contacts of TB patients (e.g., those with household exposure).

Disparities in tuberculosis burden among South Asians living in New York City, 2001-2010

OBJECTIVES

We have described the characteristics of South Asian-born tuberculosis (TB) patients living in New York City (NYC) and compared them with other foreign-born patients to explore possible explanations for the disproportionate burden of TB in the South Asian population.

METHODS

We used data on demographic and clinical characteristics for TB patients identified by the NYC Bureau of Tuberculosis Control from 2001 to 2010 to compare South Asian patients with other Asian and other foreign-born patients. We reviewed genotyping and cluster investigation data for South Asian patients to assess the extent of genotype clustering and the possibility of local transmission in this population.

RESULTS

The observed disparity in TB rates and burden among South Asians was not explained by social or clinical characteristics. A large amount of TB strain diversity was observed among South Asians, and they were less likely than other foreign-born patients to be infected with the same TB strain as another NYC patient.

CONCLUSIONS

The majority of South Asians were likely infected with TB abroad. South Asians represent a meaningful foreign-born subpopulation for targeted detection and treatment of TB infection in NYC.

Increasing the efficiency and yield of a tuberculosis contact investigation through electronic data systems matching

BACKGROUND

Electronic health data may improve the timeliness and accuracy of resource-intense contact investigations (CIs) in healthcare settings.

METHODS

In September 2013, we initiated a CI around a healthcare worker (HCW) with infectious tuberculosis (TB) who worked in a maternity ward. Two sources of electronic health data were employed: hospital-based electronic medical records (EMRs), to identify patients exposed to the HCW, and an electronic immunization registry, to obtain contact information for exposed infants and their providers at two points during follow-up.

RESULTS

Among 954 patients cared for in the maternity ward during the HCW's infectious period, the review of EMRs identified 285 patients (30%) who interacted with the HCW and were, thus, exposed to TB. Matching infants to the immunization registry offered new provider information for 52% and 30% of the infants in the first and second matches. Providers reported evaluation results for the majority of patients (66%).

CONCLUSION

Data matching improved the efficiency and yield of this CI, thereby demonstrating the usefulness of enhancing CIs with electronic health data.

Estimated Prevalence of Tuberculosis Infection Among a New York City Clinic Population Using Interferon-gamma Release Assays

Using QuantiFERON®-Gold In-Tube (QFT-GIT) data, the prevalence of tuberculosis infection in New York City was estimated. Patient characteristics associated with a positive result were consistent with known tuberculosis risk factors. Results suggest that blood-based tests for tuberculosis infection are reliable.

Background

 Elimination of tuberculosis (TB) in the United States requires treating not only persons with active disease but also those infected with TB. Achieving this goal requires understanding local TB infection prevalence and identifying subgroups at increased risk for infection and disease.

Methods

 The study population included all patients tested with an interferon-gamma release assay (IGRA) test at New York City (NYC) public TB clinics from October 1, 2006 to December 31, 2011. Patients who were not a case or contact at testing (general clinic patients) and who had a positive QuantiFERON-Gold In-Tube (QFT-GIT) test result were compared with those with indeterminate or negative results to identify characteristics associated with positive results. New York City TB surveillance data were used to identify clinic patients later diagnosed with active TB disease.

Results

 A total of 69 273 IGRA tests were conducted. Among 20 066 patients tested with QFT-GIT, 16% tested positive, 83% tested negative, and <1% were indeterminate. Of 18 481 general clinic patients, 14% had a positive QFT-GIT result. Nine percent of United States-born patients compared with 19% of foreign-born patients had a positive result. Increasing age and birth in a high-incidence country were associated with a higher likelihood of having a positive result. One patient with a negative QFT-GIT result was identified as a TB case 2 years later.

Conclusions

 Using QFT-GIT data, the background prevalence of TB infection in NYC was estimated. Patient characteristics associated with a positive QFT-GIT result were consistent with known TB risk factors. Results suggest that IGRAs are reliable tests for TB infection.

Congenital tuberculosis and management of exposure in three neonatal intensive care units

Congenital tuberculosis (TB) is uncommon, and diagnosis may be delayed. We report a case of congenital TB and the management of exposure in three different neonatal intensive care units. This case demonstrates the need for a high index of suspicion, active communication among maternal and neonatal medical providers, and timely provider reporting of maternal disease, and emphasizes the relatively greater risk of transmission to health care workers versus infants in this setting.

Tuberculosis rates among HIV-infected persons in New York City, 2001-2005

We calculated population-based tuberculosis (TB) rates among HIV-infected persons in New York City from 2001 through 2005 using data from the city's TB and HIV/AIDS surveillance registries, and we examined those rates using linear trend tests and incidence rate ratios (IRRs). HIV-infected individuals had 16 times the TB rate of a "non-HIV" population (HIV status negative or unknown; IRR = 16.0; 95% confidence interval = 14.9, 17.2). TB rates declined significantly among the US-born HIV-infected population (P (trend) < .001) but not among the foreign-born HIV-infected population (P (trend) = .355). Such disparities must be addressed if further declines are to be achieved.

National Injury-Related Hospitalizations in Children: Public Versus Private Expenditures Across Preventable Injury Mechanisms

BACKGROUND

Examination of expenditures in areas where more universal application of effective injury prevention approaches is indicated could identify specific mechanisms and age groups where effective intervention may impact public injury-related expenditures.

METHODS

The Healthcare Cost and Utilization Project 2003 (KID-HCUP) contains acute care hospitalization data for U.S. children and adolescents residing in 36 states. The study population includes 240,248 unweighted (397,943 weighted) injury-related hospital discharges for ages 0 to 19 years. Injury severity was assessed using ICDMAP-90 and International Classification of Injury Severity Scores (ICISS). SUDAAN was employed to adjust variances for stratified sampling. Expenditures were weighted to represent the U.S. population.

RESULTS

Injury-related hospitalizations (mean $28,137 +/- 64,420, median $10,808) were more costly than non-injury discharges, accounting for approximately 10% of all persons hospitalized (unweighted), but more than one-fifth of expenditures. Public sources were the primary payor for 37.7% of injured persons. Incidence and cost per case variations across specific injury mechanisms heavily influenced total mechanism specific expenditures. Motor vehicle crashes were the largest expenditures for private and public payors with two thirds of expenditures in teenagers - more than 40% for drivers. Medicaid covered 45.6% ($192 million) of burn expenditures and 59.2% in 0-4 year olds. Expenditures per case (mean +/- SD, median) were: firearm ($36,196 +/- 58,052, $19,020), motor vehicle driver ($33,731 +/- 50,583, $18,431), pedestrian ($31,414 +/- 57,103, $16,552); burns ($29,242 +/- 64,271, $10,739); falls ($13,069 +/- 20,225, $8,610); and poisoning ($8,290 +/- $15,462, $5,208).

CONCLUSIONS

More universal application of proven injury prevention has the potential to decrease both the public and private health expenditure burden among several modifiable injury mechanisms.

Metabolite-intermediate complexation and inhibition of microsomal CYP3A in rat liver by diltiazem

1. The formation of metabolite intermediate (MI)-complexes between cytochrome P450 (CYP) and the alkylamine-substituted drugs diltiazem (DTZ) and desipramine (DES) and their effect on CYP activities was investigated in rat liver. 2. Dexamethasone and phenobarbitone pretreatment enhanced MI-complexation by DTZ (36% and 11% of total CYP complexed, respectively), whereas beta-naphthoflavone induction was without effect. All three treatments decreased MI-complexation produced by DES. 3. After a preincubation step in NADPH-supplemented microsomes DTZ and DES were effective inhibitors of the activities of CYPs 3A and 2C11 (testosterone 6beta- and 16alpha-hydroxylations, respectively). 4. Although MI-complexation by DTZ was more extensive in microsomes from dexamethasone-induced rats, the apparent inhibition potency of the drug toward CYP activity was unchanged. By comparison, inhibition of CYP activity by DES was less pronounced than in control liver. 5. These findings indicate that drug-mediated MI-complexation of CYPs does not necessarily potentiate the inhibitory effect on monooxygenase activity, although the duration of inhibition is longer. The extent of inhibition produced by stable drug metabolites may be similar to that from MI-complexation. but their duration of action is limited by diffusion from the active site of the enzyme.

Effect of atrial radiofrequency ablation designed to cure atrial fibrillation on atrial mechanical function

INTRODUCTION

The effects of linear radiofrequency lesions in the atria for cure of atrial fibrillation on atrial contraction have not previously been quantified.

METHODS AND RESULTS

Atrial function was measured before and 30 +/- 24 days after a biatrial ablation procedure designed to cure atrial fibrillation in eight dogs and after a sham procedure in three dogs. Atrial mechanical function was assessed using Doppler diastolic blood flow velocities, atrial systolic pressure wave amplitude, and assessment of atrial contribution to cardiac output estimated by comparison of AV sequential pacing to ventricular pacing at the same heart rate. The mitral Doppler A/E velocity ratio was 1.03 +/- 0.45 before and 0.72 +/- 0.43 after ablation (P = 0.048). The tricuspid A/E ratio was 0.88 +/- 0.17 before and 0.71 +/- 0.12 after ablation (P = 0.04). The estimated atrial contribution to cardiac output was 18% +/- 9% before and 5% +/- 4% after ablation (P < 0.01). The left atrial systolic pressure wave amplitude was 2.8 +/- 1.5 mmHg before and 1.7 +/- 1.0 mmHg after ablation (P = 0.1). These changes were not observed in control dogs. Lesions covered 25% +/- 6% of the atrial endocardial surface.

CONCLUSION

Multiple linear radiofrequency lesions in the atria designed to cure atrial fibrillation may impair atrial contractility. Reduced atrial function is partly due to loss of atrial myocardial mass, but regional delays in atrial activation and splinting of the atria by scarring also may contribute.