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Incidence, Length of Stay, and Prognosis of Hospitalized Patients With Pleural EmpyemaEmpyema Hospitalizations in Denmark: A 15-Year Danish Nationwide Cohort Study FREE TO VIEW

Mette Søgaard, DVM, PhD; Rikke B. Nielsen, MSc; Mette Nørgaard, MD, PhD; Jette B. Kornum, MD, PhD; Henrik C. Schønheyder, MD, DMSc; Reimar W. Thomsen, MD, PhD
Author and Funding Information

From the Department of Clinical Epidemiology (Drs Søgaard, Nørgaard, and Thomsen and Ms Nielsen), Institute of Clinical Medicine, Aarhus University Hospital; and Department of Clinical Microbiology (Drs Kornum and Schønheyder), Aalborg Hospital, Aarhus University Hospital.

Correspondence to: Mette Søgaard, DVM, PhD, Department of Clinical Epidemiology, Olof Palmes Allé 43-45, 8200 Aarhus N, Denmark; e-mail: mette.soegaard@ki.au.dk


Funding/Support: This study was supported by the Klinisk Epidemiologisk Forskningsfond at Aarhus University.

Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Schønheyder is coinventor of a patent for an adjuvant of conjugated pneumococcal vaccine. Drs Søgaard, Nørgaard, Kornum, and Thomsen and Ms Nielsen have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(1):189-192. doi:10.1378/chest.13-1912
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To the Editor:

Empyema hospitalization rates appear to be increasing in western populations, but updated population-based data are sparse. The few existing population-based studies of adult empyema have reported increases between 30% and 97% over the past decades in the United States and Canada.1-4 Most of these studies were conducted in large referral centers only.

We examined health registries covering all Danish hospitals for temporal changes in nationwide incidence, length of hospital stay, and 30-day mortality associated with empyema-related hospitalizations during 1997 to 2011. We included all patients aged ≥ 15 years receiving a first-time diagnosis of empyema (International Classification of Diseases, 10th Revision, codes J86.0 and J86.9). The positive predictive value of these empyema codes is approximately 90%.5

In total, 6,878 hospitalized patients had empyema in Denmark during 1997 to 2011. More than 40% had preexisting comorbidities, and this proportion increased over time (Table 1). The median length of hospital stay decreased from 22 days (interquartile range, 12-43 days) to 17 days (interquartile range, 10-28 days). The age- and sex-standardized incidence rate (IR) increased by 26% from 8.7 per 100,000 person-years in 1997 to 11.8 per 100,000 person-years in 2011. The IR increased the most among older people aged ≥ 80 years (87.3% [from 20.4 per 100,000 in 1997 to 38.2 per 100,000 in 2011]) compared with people aged 40 to 64 years (27.8% [from 10.7 per 100,000 in 1997 to 12.6 per 100,000 in 2011]) (Fig 1). Rates among those aged 15 to 39 years fluctuated around 2.5 to 3.5 per 100,000 person-years. Rates were 1.7- to 3.1-fold higher in men than in women, and the IR rose sharply with increasing age. The crude 30-day mortality improved modestly from 10.5% from 1997 to 2001 to 9.0% from 2007 to 2011, corresponding to an adjusted 30-day mortality rate ratio of 0.69 (95% CI, 0.57-0.84) (Table 1). Thirty-day mortality ranged from only 1.2% in patients aged 15 to 39 years to 20.2% in those aged ≥ 80 years. Mortality also varied substantially according to level of comorbidity.

Table Graphic Jump Location
Table 1 —Temporal Trends in Crude and Adjusted Mortality Within 30 d Among Patients With a First-Time Hospitalization for Empyema

Data are presented as No. (%) unless otherwise indicated. CCI = Charlson Comorbidity Index; MRR = mortality rate ratio; ref = reference.

a 

Adjusted for age, sex, comorbidity, and alcoholism-related conditions.

Figure Jump LinkFigure 1. A, B, Incidence rates of first-time hospitalization with empyema in women (A) and men (B) according to age group in Denmark, 1997 to 2011.Grahic Jump Location

The finding of an increasing empyema incidence over the past 15 years is in-line with previous studies1-3; however, the present study may be the first to examine nationwide trends in 30-day mortality following empyema. Short-term mortality is likely to be closely related to the infection, and it is notable that comorbidity had such a strong influence on 30-day mortality. Importantly, we found improvements in empyema survival over time, in particular when taking increasing patient comorbidity into account. Advanced age and comorbidity are strong prognostic factors, and empyema remains a serious condition requiring a long hospital stay.

Acknowledgments

Role of sponsors: The sponsor had no role in the design of the study, the collection and analysis of the data, or the preparation of the manuscript.

Grijalva CG, Zhu Y, Nuorti JP, Griffin MR. Emergence of parapneumonic empyema in the USA. Thorax. 2011;66(8):663-668. [CrossRef] [PubMed]
 
Finley C, Clifton J, Fitzgerald JM, Yee J. Empyema: an increasing concern in Canada. Can Respir J. 2008;15(2):85-89. [PubMed]
 
Farjah F, Symons RG, Krishnadasan B, Wood DE, Flum DR. Management of pleural space infections: a population-based analysis. J Thorac Cardiovasc Surg. 2007;133(2):346-351. [CrossRef] [PubMed]
 
Bender JM, Ampofo K, Sheng X, Pavia AT, Cannon-Albright L, Byington CL. Parapneumonic empyema deaths during past century, Utah. Emerg Infect Dis. 2009;15(1):44-48. [CrossRef] [PubMed]
 
Søgaard M, Kornum JB, Schønheyder HC, Thomsen RW. Positive predictive value of the ICD-10 hospital diagnosis of pleural empyema in the Danish National Registry of Patients. Clin Epidemiol. 2011;3(1):85-89. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1. A, B, Incidence rates of first-time hospitalization with empyema in women (A) and men (B) according to age group in Denmark, 1997 to 2011.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 —Temporal Trends in Crude and Adjusted Mortality Within 30 d Among Patients With a First-Time Hospitalization for Empyema

Data are presented as No. (%) unless otherwise indicated. CCI = Charlson Comorbidity Index; MRR = mortality rate ratio; ref = reference.

a 

Adjusted for age, sex, comorbidity, and alcoholism-related conditions.

References

Grijalva CG, Zhu Y, Nuorti JP, Griffin MR. Emergence of parapneumonic empyema in the USA. Thorax. 2011;66(8):663-668. [CrossRef] [PubMed]
 
Finley C, Clifton J, Fitzgerald JM, Yee J. Empyema: an increasing concern in Canada. Can Respir J. 2008;15(2):85-89. [PubMed]
 
Farjah F, Symons RG, Krishnadasan B, Wood DE, Flum DR. Management of pleural space infections: a population-based analysis. J Thorac Cardiovasc Surg. 2007;133(2):346-351. [CrossRef] [PubMed]
 
Bender JM, Ampofo K, Sheng X, Pavia AT, Cannon-Albright L, Byington CL. Parapneumonic empyema deaths during past century, Utah. Emerg Infect Dis. 2009;15(1):44-48. [CrossRef] [PubMed]
 
Søgaard M, Kornum JB, Schønheyder HC, Thomsen RW. Positive predictive value of the ICD-10 hospital diagnosis of pleural empyema in the Danish National Registry of Patients. Clin Epidemiol. 2011;3(1):85-89. [CrossRef] [PubMed]
 
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