Reports that septic shock incidence is rising and mortality rates declining may be confounded by improving recognition of sepsis and changing coding practices. We compared trends in septic shock incidence and mortality in academic hospitals using clinical versus claims data.
We identified all patients with concurrent blood cultures, antibiotics, and ≥2 consecutive days of vasopressors and all patients with ICD-9 codes for septic shock at 27 academic hospitals from 2005-2014. We compared annual incidence and mortality trends. We reviewed 967 records from 3 hospitals to estimate the accuracy of each method.
Of 6.5 million adult hospitalizations, 99,312 (1.5%) were flagged by clinical criteria, 82,350 (1.3%) by ICD-9 codes, and 44,651 (0.7%) by both. Sensitivity for clinical criteria was higher than claims (74.8% vs. 48.3%, p<0.01), whereas positive predictive value was comparable (83% vs. 89%, p=0.23). Septic shock incidence using clinical criteria rose from 12.8 to 18.6 cases per 1000 hospitalizations (average 4.9% increase/year, 95% CI 4.0%-5.9%), while mortality declined from 54.9% to 50.7% (average 0.6% decline/year, 95% CI 0.4%-0.8%). In contrast, septic shock incidence using I0CD-9 codes increased from 6.7 to 19.3 per 1000 hospitalizations (19.8% increase/year, 95% CI 16.6%-20.9%), while mortality decreased from 48.3% to 39.3% (1.2% decline/year, 95% CI 0.9%-1.6%).
A clinical surveillance definition based on concurrent vasopressors, blood cultures, and antibiotics accurately identifies septic shock hospitalizations and suggests that the incidence of patients receiving treatment for septic shock has risen and mortality rates have fallen, but less dramatically than estimated using ICD-9 codes.