Burden of CAP Requiring Hospitalization High for US Adults

Pam Harrison

July 14, 2015

The burden of community-acquired pneumonia (CAP) requiring hospitalization among US adults is substantial and is markedly higher among the oldest adults, an active-population-based surveillance has found.

Moreover, pathogens were not identified for nearly two thirds of patients, researchers report in an article published online July 14 in the New England Journal of Medicine.

Seema Jain, MD, from the Centers for Disease Control and Prevention, Atlanta, Georgia, and colleagues found that the estimated incidence of hospitalization for pneumonia among adults aged 50 to 64 years was four times higher than the incidence among adults between 18 and 49 years of age.

For adults between 65 and 79 years of age, the estimated incidence of hospitalization for pneumonia was nine times higher than that of younger adults, and for individuals 80 years of age and older, the estimated incidence was 25 times higher.

The researchers also found that a pathogen was detected in just 38% of samples from 2259 patients who had radiographic evidence of pneumonia and specimens available for both bacterial and viral testing. Among those cases, tests identified one or more viruses in 23% of samples, bacteria in 11%, bacterial and viral pathogens in 3%, and a fungal or mycobacterial pathogen in 1%.

The most common pathogen was human rhinovirus, found in 9% of patients, followed by influenza virus in 6% and Streptococcus pneumoniae in 5%.

Some 21% of patients required admission to the intensive care unit (ICU), with 6% requiring invasive mechanical ventilation. Two percent of the patients died during hospitalization.

"The [Etiology of Pneumonia in the Community (EPIC)] study was a large, contemporary, prospective, population-based study of [CAP] in hospitalized adults in the United States," Dr Jain and colleagues write.

"These data suggest that improving the coverage and effectiveness of recommended influenza and pneumococcal vaccines and developing effective vaccines and treatments for [human metapneumovirus], [respiratory syncytial virus], and parainfluenza virus infection could reduce the burden of pneumonia among adults."

Study Covered Five Hospitals in Two Cities

The EPIC study was an active population-based surveillance project designed to estimate the incidence of radiographically confirmed pneumonia requiring hospitalization among adults 18 years of age or older in five hospitals in Chicago, Illinois, and Nashville, Tennessee.

Patients who had been recently hospitalized or who were severely immunosuppressed were excluded.

From January 2010 through June 2012, investigators enrolled 2488 (68%) of 3634 eligible adults. Blood, urine, and respiratory specimens were systematically collected for culture, serologic testing, antigen detection, and molecular diagnostic testing.

The median age of patients was 57 years, and 93% of the cohort had radiographic evidence of pneumonia.

The overall annual incidence of pneumonia was 24.8 cases per 10,000 adults (95% confidence interval, 23.5 - 26.1 cases), with the highest rates occurring among adults from 65 to 79 years of age (63.0 cases per 10,000 adults) and among those 80 years of age or older (164.3 per 10,000 adults).

"Despite current diagnostic tests, no pathogen was detected in the majority of patients," Dr Jain and colleagues observe.

"[But] for each pathogen, the incidence increased with age."

In fact, the incidences of influenza and of Streptococcus pneumonia were almost five times as high among adults 65 years of age or older than among younger adults, and the incidence of human rhinovirus was almost 10 times higher among older compared with younger adults.

In addition, three pathogens were detected more commonly in patients in the intensive care unit than in patients not in the intensive care unit: S. pneumoniae, Staphylococcus aureus, and Enterobacteriaceae (P < .001 for all comparisons).

The fact that respiratory viruses were more frequently detected than bacteria probably reflects the direct and indirect benefit of bacterial vaccines and relatively insensitive diagnosis tests, the authors suggest.

"Further development of new rapid diagnostic tests that can accurately identify and distinguish among potential pneumonia pathogens is needed," the authors suggest.

The study was funded by the Influenza Division of the National Center for Immunizations and Respiratory Diseases. One or more coauthors reports research support, paid to his or her institution, from Cubist Pharmaceuticals, GlaxoSmithKline, Thermo Scientific BRAHMS, and Juvaris Bio-Therapeutics, Inc. One or more coauthors reports receiving grants, fees, editorial support, or consultant fees from one or more of the following companies: MedImmune, Roche, AbbVie, Pfizer, GlaxoSmithKline, Antimicrobial Therapy Inc, Medscape Inc, BioFire Dx, CareFusion, bioMerieux, Affinium Pharmaceuticals, Astute Medical, Crucell Holland BV, BRAHMS GmbH, Rapid Pathogen Screening, Venaxis, Cempra Pharmaceuticals, Accelerate Diagnostics, Vertex, Tetraphase, Genetech/Roche, Rempex, Vical, Bayer, Cerexa, and Visterra Inc.

N Engl J Med. Published online July 14, 2015.

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