title: Validity of the International Classification of Diseases 10th revision code for hyperkalaemia in elderly patients at presentation to an emergency department and at hospital admission.
abstract: OBJECTIVE
  Evaluate the validity of the International Classification of Diseases, 10th revision (ICD-10) code for hyperkalaemia (E87.5) in two settings: at presentation to an emergency department and at hospital admission.
  
  
  METHODS
  Population-based validation study.
  
  
  METHODS
  12 hospitals in Southwestern Ontario, Canada, from 2003 to 2010.
  
  
  METHODS
  Elderly patients with serum potassium values at presentation to an emergency department (n=64 579) and at hospital admission (n=64 497).
  
  
  METHODS
  Sensitivity, specificity, positive-predictive value and negative-predictive value. Serum potassium values in patients with and without a hyperkalaemia code (code positive and code negative, respectively).
  
  
  RESULTS
  The sensitivity of the best-performing ICD-10 coding algorithm for hyperkalaemia (defined by serum potassium >5.5 mmol/l) was 14.1% (95% CI 12.5% to 15.9%) at presentation to an emergency department and 14.6% (95% CI 13.3% to 16.1%) at hospital admission. Both specificities were greater than 99%. In the two settings, the positive-predictive values were 83.2% (95% CI 78.4% to 87.1%) and 62.0% (95% CI 57.9% to 66.0%), while the negative-predictive values were 97.8% (95% CI 97.6% to 97.9%) and 96.9% (95% CI 96.8% to 97.1%). In patients who were code positive for hyperkalaemia, median (IQR) serum potassium values were 6.1 (5.7 to 6.8) mmol/l at presentation to an emergency department and 6.0 (5.1 to 6.7) mmol/l at hospital admission. For code-negative patients median (IQR) serum potassium values were 4.0 (3.7 to 4.4) mmol/l and 4.1 (3.8 to 4.5) mmol/l in each of the two settings, respectively.
  
  
  CONCLUSIONS
  Patients with hospital encounters who were ICD-10 E87.5 hyperkalaemia code positive and negative had distinct higher and lower serum potassium values, respectively. However, due to very low sensitivity, the incidence of hyperkalaemia is underestimated.
authors.affiliation: Division of Nephrology, Department of Medicine,  Western University, London,  Canada.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Fleet
authors.forename: Salimah Z
authors.initials: SZ
authors.lastname: Shariff
authors.forename: Sonja
authors.initials: S
authors.lastname: Gandhi
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Weir
authors.forename: Arsh K
authors.initials: AK
authors.lastname: Jain
authors.forename: Amit X
authors.initials: AX
authors.lastname: Garg