Association of Diagnosis Coding with Differences in Risk-Adjusted Short-term Mortality between Critical Access and Non-Critical Access Hospitals

Cyrus M. Kosar, Lacey Loomer, Kali S. Thomas, Elizabeth M. White, Orestis A. Panagiotou, Momotazur Rahman

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Importance: Critical access hospitals (CAHs) provide care to rural communities. Increasing mortality rates have been reported for CAHs relative to non-CAHs. Because Medicare reimburses CAHs at cost, CAHs may report fewer diagnoses than non-CAHs, which may affect risk-adjusted comparisons of outcomes.

Objective: To assess serial differences in risk-adjusted mortality rates between CAHs and non-CAHs after accounting for differences in diagnosis coding.

Design, Setting, and Participants: Serial cross-sectional study of rural Medicare Fee-for-Service beneficiaries admitted to US CAHs and non-CAHs for pneumonia, heart failure, chronic obstructive pulmonary disease, arrhythmia, urinary tract infection, septicemia, and stroke from 2007 to 2017. The final date of follow-up was December 31, 2017.

Exposure: Admission to a CAH vs non-CAH.

Main Outcomes and Measures: Discharge diagnosis count including trends from 2010 to 2011 when Medicare expanded the allowable number of billing codes for hospitalizations, and combined in-hospital and 30-day postdischarge mortality adjusted for demographics, primary diagnosis, preexisting conditions, and with vs without further adjustment for Hierarchical Condition Category (HCC) score to understand the contribution of in-hospital secondary diagnoses.

Results: There were 4 094 720 hospitalizations (17% CAH) for 2 850 194 unique Medicare beneficiaries (mean [SD] age, 76.3 [11.7] years; 55.5% women). Patients in CAHs were older (median age, 80.1 vs 76.8 years) and more likely to be female (58% vs 55%). In 2010, the adjusted mean discharge diagnosis count was 7.52 for CAHs vs 8.53 for non-CAHs (difference, -0.99 [95% CI, -1.08 to -0.90]; P < .001). In 2011, the CAH vs non-CAH difference in diagnoses coded increased (P < .001 for interaction between CAH and year) to 9.27 vs 12.23 (difference, -2.96 [95% CI, -3.19 to -2.73]; P < .001). Adjusted mortality rates from the model with HCC were 13.52% for CAHs vs 11.44% for non-CAHs (percentage point difference, 2.08 [95% CI, 1.74 to 2.42]; P < .001) in 2007 and increased to 15.97% vs 12.46% (difference, 3.52 [95% CI, 3.09 to 3.94]; P < .001) in 2017 (P < .001 for interaction). Adjusted mortality rates from the model without HCC were not significantly different between CAHs and non-CAHs in all years except 2007 (12.19% vs 11.74%; difference, 0.45 [95% CI, 0.12 to 0.79]; P = .008) and 2010 (12.71% vs 12.28%; difference, 0.42 [95% CI, 0.07 to 0.77]; P = .02).

Conclusions and Relevance: For rural Medicare beneficiaries hospitalized from 2007 to 2017, CAHs submitted significantly fewer hospital diagnosis codes than non-CAHs, and short-term mortality rates adjusted for preexisting conditions but not in-hospital comorbidity measures were not significantly different by hospital type in most years. The findings suggest that short-term mortality outcomes at CAHs may not differ from those of non-CAHs after accounting for different coding practices for in-hospital comorbidities.

Original languageEnglish (US)
Pages (from-to)481-487
Number of pages7
JournalJAMA - Journal of the American Medical Association
Issue number5
StatePublished - Aug 4 2020

Bibliographical note

Funding Information:
reported receiving grants from the National Institute on Aging (NIA) unrelated to the current study and personal fees from the American Health Care Association outside the submitted work. Dr White reported receiving grants from the Agency for Healthcare Research and Quality during the conduct of the study. No other disclosures were reported.

Funding Information:
Funding/Support: This study was funded by the NIA (grants 5R21AG053712-02, P01AG027296, and 5R03AG054687-02).

Publisher Copyright:
© 2020 American Medical Association. All rights reserved.


  • Aged
  • Aged, 80 and over
  • Chronic Disease/classification
  • Clinical Coding
  • Cross-Sectional Studies
  • Fee-for-Service Plans
  • Female
  • Hospital Mortality
  • Hospitalization/statistics & numerical data
  • Hospitals, Rural
  • Humans
  • Male
  • Medicare
  • Patient Discharge Summaries
  • Risk Adjustment
  • United States/epidemiology

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural


Dive into the research topics of 'Association of Diagnosis Coding with Differences in Risk-Adjusted Short-term Mortality between Critical Access and Non-Critical Access Hospitals'. Together they form a unique fingerprint.

Cite this