Trends in US Hospital Admissions for Skin and Soft Tissue Infections

Using data from the 2000-2004 US Healthcare Cost and Utilization Project National Inpatient Sample, we found that total hospital admissions for skin and soft tissue infections increased by 29% during 2000-2004; admissions for pneumonia were largely unchanged.These results are consistent with recent reported increases in community-associated methicillin-resistant Staphylococcus aureus infections.uring 1998-2004, Staphylococcus aureus was the most common cause of skin and soft tissue infections (SSTIs) in North America; frequency of these infections was 44.6%, and the rate of methicillin resistance among the isolates was 35.9% (1).Over the past decade, community-associated methicillin-resistant S. aureus (CA-MRSA) has become a notable public health problem; it accounts for 14% of invasive infections nationwide and 59% (range 15%-74%) of SSTIs among patients seeking treatment at emergency departments in 11 US cities (2,3).The emergence of CA-MRSA infections may have resulted in increased numbers of hospitalizations for SS-TIs because of an increasing incidence of antimicrobial drug failure in outpatient treatment and more aggressive approaches to the management of these infections by physicians who are aware of the heightened risk of becoming infected with CA-MRSA.To determine whether hospital admissions for CA-MRSA are increasing, we analyzed data from the Healthcare Cost and Utilization Project National Inpatient Sample. D The StudyThis study was based on data from the Healthcare Cost and Utilization Project National Inpatient Sample (HCUP NIS) for the 5-year period 2000-2004.HCUP NIS is a stratified random sample from ≈20% of all US community hospitals.For 2004, the NIS contains all discharge data from >1,000 acute-care hospitals in 37 states, representing >8 million hospital stays.We identified all hospital admissions in the HCUP NIS for which a principal diagnosis of SSTI was given.As defined by the Uniform Hospital Discharge Data Set, principal diagnosis is the condition "established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care" (http://wonder.cdc.gov).SSTIs were defined as the following: 1) acute lymphadenitis (International Classification of Diseases, 9th Revision, Clinical Modification [ICD-9-CM] 683.XX); 2) carbuncle and furuncle (680.XX); 3) cellulitis and abscess of finger and toe (681.XX); 4) impetigo (684.XX); 5) infection (chronic) of amputation stump (997.62); 6) other cellulitis and abscess (682.XX); 7) other local infections of skin and subcutaneous tissue (686.XX); 8) abscess of anal and rectal regions (566); 9) chronic ulcer of other specified sites (707.8);10) chronic ulcer of unspecified site (707.9);11) decubitus ulcer (707); 12) infection due to other vascular device implant and graft (996.62);13) pilonidal cyst with abscess (685); 14) postoperative wound infection (998.5X);15) posttraumatic wound infection, not elsewhere classified (958.3);16) ulcers of lower limbs, except decubitus (707.1X);17) gangrene (785.4); and 18) necrotizing fasciitis (728.86).To aid in interpretation of the data, we grouped the above-listed SSTIs into 3 mutually exclusive categories: 1) superficial infections predominantly caused by S. aureus or Streptococcus pyogenes (groups 1-7 above); 2); deeper or healthcare-associated infections more likely to involve anaerobic or gram-negative organisms (groups 8-16); and 3) infections typically associated with a high rate of mortality (groups 17-18).For each year of interest, all SSTI admissions were then stratified by type of infection and selected patient and hospital characteristics.To provide a benchmark against which to interpret possible trends in SSTI-related hospital admissions, we generated similar series for all admissions with a principal diagnosis of infectious pneumonia, another common type of infection that frequently results in hospitalization but for which no trends were expected.Infectious pneumonia was defined to include 1) pneumococcal pneumonia (ICD-9-CM 481); 2) other bacterial pneumonia (482.XX)