Reliability of comorbidity scores derived from administrative data in the tertiary hospital intensive care setting: a cross-sectional study

Background Hospital reporting systems commonly use
administrative data to calculate comorbidity scores in
order to provide risk-adjustment to outcome indicators.
Objective We aimed to elucidate the level of agreement
between administrative coding data and medical chart
review for extraction of comorbidities included in the
Charlson Comorbidity Index (CCI) and Elixhauser Index
(EI) for patients admitted to the intensive care unit of a
university-affiliated hospital.
Method We conducted an examination of a random
cross-section of 100 patient episodes over 12 months (July
2012 to June 2013) for the 19 CCI and 30 EI comorbidities
reported in administrative data and the manual medical
record system. CCI and EI comorbidities were collected in
order to ascertain the difference in mean indices, detect
any systematic bias, and ascertain inter-rater agreement.
Results We found reasonable inter-rater agreement
(kappa (κ) coefficient ≥0.4) for cardiorespiratory and
oncological comorbidities, but little agreement (κ<0.4)
for other comorbidities. Comorbidity indices derived from
administrative data were significantly lower than from
chart review: −0.81 (95% CI − 1.29 to − 0.33; p=0.001)
for CCI, and −2.57 (95% CI −4.46 to −0.68; p=0.008) for
EI.
Conclusion While cardiorespiratory and oncological
comorbidities were reliably coded in administrative data,
most other comorbidities were under-reported and an
unreliable source for estimation of CCI or EI in intensive
care patients. Further examination of a large multicentre
population is required to confirm our findings.