Epidemiologic Inference in Outbreak Investigation

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Trends and risk factors for pneumonia among HIV
infected and uninfected injection drug users
Stein K, Astemborski J, Mehta SH, Nelson K,
Vlahov D, Galai N, Kirk GD Johns Hopkins
University Departments of Epidemiology Medicine
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Background

• Community-acquired bacterial pneumonia is a
  common cause of morbidity mortality among HIV
  infected persons, especially among injection drug
  users
• Effects of HAART on pneumonia incidence are not
  well defined
• Prior studies limited by lack of data to compare
• HIV infected vs. uninfected IDUs
• HIV treated vs. untreated
• males vs. females

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Objective

• To characterize temporal trends of bacterial
  pneumonia among HIV infected and uninfected IDUs
  before and after HAART availability
• To identify risk factors for pneumonia and
  contrast these factors by HIV status

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AIDS Linked to the Intra-Venous Experience Cohort
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Pneumonia Cases

• Clinical Case Definition Chest X-ray infiltrates
  and 1 of 3 clinical findings fever, productive
  cough, leukocytosis
• 36 with sputum or blood culture confirmation
• No evidence for other etiologic agents
• Pneumocystis jirovecii, mycobacteria, fungal,
  viral pathogens
• Excluded cases when pneumonia diagnosis made gt72
  hrs after admission

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Statistical Analyses

• Pneumonia rates determined using person-time
  analysis
• Kaplan-Meier curves by HIV/CD4 strata. Cox
  Proportional Hazards models used to identify
  determinants of pneumonia while adjusting for
  other factors
• Time-dependent covariates determined at study
  visit prior to pneumonia diagnosis

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Characteristics of ALIVE Participants at Study
Entry
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Temporal Trends in Pneumonia Rates
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Time to First Bacterial Pneumoniaby HIV Status
and CD4 Cell Count
HIV-
HIV / CD4 gt500
HIV / CD4 200-499
HIV / CD4 100-199
HIV / CD4 lt100
P value lt 0.05 for differences between groups
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Infected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Infected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Infected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Uninfected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Uninfected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Uninfected IDUs
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Temporal Trends in Pneumonia Rates
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Temporal Trends in Pneumonia Rates Increasing
HAART Uptake
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Summary

• Trend Analysis
• Pneumonia rates in HIV-infected IDUs have
  dramatically declined in past decade, coincident
  with increasing HAART use and declining injection
  drug use.
• Risk Factor Analysis
• HIV seropositivity
• Decreasing CD4 count
• HAART use protective
• Age, female gender
• Prior endocarditis / bacteremia
• Heavy drug use
• Heavy cigarette smoking

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Conclusions

• Many risk factors for pneumonia among injection
  drug users are modifiable, yet remain highly
  prevalent.
• Increasing access to HAART, drug treatment and
  smoking cessation programs may result in further
  declines in morbidity and mortality from
  pneumonia among IDUs.

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Acknowledgements

• NIDA funding (DA04334 DA12568)
• ALIVE Investigators, Clinic and Study Staff
• Neil Graham, Waleska Caiaffa, Tim Sterling, David
  Thomas, Greg Lucas, Stephanie Strathdee, Melody
  Schaeffer
• Study participants

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Proportion of Culture Confirmed Pneumonia Cases
by Organism
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Temporal Trends in Pneumonia Rates Decreasing
Injection Drug Use
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Infected IDUs
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Multivariate Analysis of Pneumonia Risk Factors
among HIV Uninfected IDUs
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