How many diagnosis fields are needed to capture safety events in administrative data? Findings and recommendations from the WHO ICD-11 Topic Advisory Group on Quality and Safety

Int J Qual Health Care. 2014 Feb;26(1):16-25. doi: 10.1093/intqhc/mzt090. Epub 2013 Dec 13.


Objective: As part of the WHO ICD-11 development initiative, the Topic Advisory Group on Quality and Safety explores meta-features of morbidity data sets, such as the optimal number of secondary diagnosis fields.

Design: The Health Care Quality Indicators Project of the Organization for Economic Co-Operation and Development collected Patient Safety Indicator (PSI) information from administrative hospital data of 19-20 countries in 2009 and 2011. We investigated whether three countries that expanded their data systems to include more secondary diagnosis fields showed increased PSI rates compared with six countries that did not. Furthermore, administrative hospital data from six of these countries and two American states, California (2011) and Florida (2010), were analysed for distributions of coded patient safety events across diagnosis fields.

Results: Among the participating countries, increasing the number of diagnosis fields was not associated with any overall increase in PSI rates. However, high proportions of PSI-related diagnoses appeared beyond the sixth secondary diagnosis field. The distribution of three PSI-related ICD codes was similar in California and Florida: 89-90% of central venous catheter infections and 97-99% of retained foreign bodies and accidental punctures or lacerations were captured within 15 secondary diagnosis fields.

Conclusions: Six to nine secondary diagnosis fields are inadequate for comparing complication rates using hospital administrative data; at least 15 (and perhaps more with ICD-11) are recommended to fully characterize clinical outcomes. Increasing the number of fields should improve the international and intra-national comparability of data for epidemiologic and health services research, utilization analyses and quality of care assessment.

Keywords: diagnosis-related groups; international classification of diseases; patient safety; quality indicators; risk adjustment; world health organization.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Advisory Committees
  • Aged
  • Aged, 80 and over
  • California
  • Diagnosis
  • Female
  • Florida
  • Humans
  • International Classification of Diseases* / organization & administration
  • International Classification of Diseases* / standards
  • Male
  • Middle Aged
  • Patient Safety / standards
  • Patient Safety / statistics & numerical data*
  • Quality Indicators, Health Care / organization & administration
  • Quality Indicators, Health Care / standards
  • Quality Indicators, Health Care / statistics & numerical data
  • Quality of Health Care / organization & administration
  • Quality of Health Care / statistics & numerical data
  • Young Adult