Methods: Demographic and clinical data were obtained from the UCM Clinical Data Warehouse for patient encounters with an ICD-9-coded SSTI diagnosis in January 2006 - March 2014. Repeat encounters for a single patient in each year were excluded. Incidence density was calculated per 1,000 encounters by quarter and year and stratified by inpatient, outpatient clinic and emergency department (ED) encounters; and by age group, gender and race. Poisson regression was performed to assess change over time.
Results: In 2006-14, data were analyzed for 38,201 SSTI-associated encounters from 31,869 subjects. Among all patients treated at UCM, there was a decrease of 1% per year in the incidence of SSTIs in 2006-13, with an overall decrease of 16%, from 6.17 per 1,000 encounters in 2006 to 5.13 per 1,000 encounters in 2013 (rate ratio [RR] = 0.97, 95% CI: 0.97 – 0.98). There was a significant decrease in SSTI-related encounters among inpatients (RR = 0.97, 95% CI: 0.96 – 0.98), ED patients (RR = 0.98, 95% CI: 0.97 – 0.98), adults (RR = 0.98, 95% CI: 0.97 – 0.98), children (RR = 0.96, 95% CI: 0.95 – 0.97) and African Americans (RR = 0.99, 95% CI: 0.98 – 0.99). SSTIs increased significantly only among clinic outpatients (RR = 1.01, 95% CI: 1.00 – 1.02). Children, compared with adults, had a significantly higher likelihood of having an encounter related to an SSTI (RR = 1.81, 95% CI: 1.77 – 1.85). Compared with outpatient clinic encounters, there was a higher rate of SSTIs among both inpatient (RR = 9.07, 95% CI: 8.80 – 9.35) and ED encounters (RR = 9.22, 95% CI: 9.01 – 9.42). Both overall pediatric and overall ED SSTI encounters exhibited a strong seasonal pattern, with a peak incidence each year during the third quarter.
Conclusion: The incidence of SSTIs at UCM decreased in children and adults treated as inpatients and in the ED. There was marked seasonal variation, peaking during the summer months. This suggests a reversal of the massive increase in SSTI incidence after 2000 in the U.S.
M. Z. David, None
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