Risk of hemolytic uremic syndrome after sporadic Escherichia coli O157:H7 infection
Risk of hemolytic uremic syndrome after sporadic Escherichia coli O157:H7 infection: results of a Canadian collaborative study. Rowe PC, Orrbine E, Lior H, Wells GA, Yetisir E, Clulow M, McLaine PN, and the Investigators of the Canadian Pediatric Kidney Disease Research Center. Journal of Pediatrics 1998; 132(5):777-782.
The risk of hemolytic uremic syndrome (HUS) for the individual child with acute Escherichia coli O157:H7 infection has been estimated to range from 3% to 26% after sporadic gastroenteritis and from 0% to 23% in the larger foodborne and community epidemics. Higher rates are reported from tertiary care centers, because patients referred to these centers tend to have more severe illness. In contrast, studies of outbreaks may underestimate the risk, because they rarely include laboratory testing to identify children with subclinical HUS or clinically important hemolytic anemia. The objectives of this study were to better estimate the age-specific risks of HUS and hemolytic anemia after E. coli O157:H7 infection among a representative cohort of both referred and nonreferred children with documented illness from the province of Alberta and to compare this with the rates in children evaluated at referral centers in the rest of Canada. Children with HUS or E. coli O157:H7 gastroenteritis were eligible if they were less than 15 years of age. Hemoglobin, blood smear, urinalysis, and serum creatinine were obtained 8 to 10 days after the onset of diarrhea to ascertain hemolysis, anemia, thrombocytopenia, and renal injury. Subjects were monitored for one month. From June 1991 to March 1994, HUS was diagnosed in 205 children. Of these 77% had evidence of E. coli O157:H7 infection. A further 582 children had E. coli O157:H7 gastroenteritis, of whom 18 had hemolytic anemia. The risk of HUS after E. coli O157:H7 infection in Alberta was 8.1% compared with 31.4% in referral centers in the rest of Canada. In Alberta, the highest age-specific risk of HUS/hemolytic anemia was 12.9% in those less than 5 years of age. The authors suggest that these data should help guide clinical decisions regarding laboratory surveillance once E. coli O157:H7 is identified and provide a basis for estimating the sample sizes required in future treatment trials for the secondary prevention of HUS.