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Validation of discharge diagnosis codes to identify serious infections among middle age and older adults
Andrew D Wiese1, Marie R Griffin1,2, C Michael Stein3
1Department of Health Policy, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Objectives:
Hospitalisations for serious infections are common among middle age and older adults and frequently used as study outcomes. Yet, few studies have evaluated the performance of diagnosis codes to identify serious infections in this population. We sought to determine the positive predictive value (PPV) of diagnosis codes for identifying hospitalisations due to serious infections among middle age and older adults.
Setting And Participants:
We identified hospitalisations for possible infection among adults >=50 years enrolled in the Tennessee Medicaid healthcare programme (2008-2012) using International Classifications of Diseases, Ninth Revision diagnosis codes for pneumonia, meningitis/encephalitis, bacteraemia/sepsis, cellulitis/soft-tissue infections, endocarditis, pyelonephritis and septic arthritis/osteomyelitis.
Design:
Medical records were systematically obtained from hospitals randomly selected from a stratified sampling framework based on geographical region and hospital discharge volume.
Measures:
Two trained clinical reviewers used a standardised extraction form to abstract information from medical records. Predefined algorithms served as reference to adjudicate confirmed infection-specific hospitalisations. We calculated the PPV of diagnosis codes using confirmed hospitalisations as reference. Sensitivity analyses determined the robustness of the PPV to definitions that required radiological or microbiological confirmation. We also determined inter-rater reliability between reviewers.
Results:
The PPV of diagnosis codes for hospitalisations for infection (n=716) was 90.2% (95% CI 87.8% to 92.2%). The PPV was highest for pneumonia (96.5% (95% CI 93.9% to 98.0%)) and cellulitis (91.1% (95% CI 84.7% to 94.9%)), and lowest for meningitis/encephalitis (50.0% (95% CI 23.7% to 76.3%)). The adjudication reliability was excellent (92.7% agreement; first agreement coefficient: 0.91). The overall PPV was lower when requiring microbiological confirmation (45%) and when requiring radiological confirmation for pneumonia (79%).
Conclusions:
Discharge diagnosis codes have a high PPV for identifying hospitalisations for common, serious infections among middle age and older adults. PPV estimates for rare infections were imprecise.
Insights
Diagnosis codes accurately identify serious infections in older adults, with a 90.2% positive predictive value (PPV). However, PPV for rare infections was imprecise, highlighting the need for careful interpretation in clinical research.
Area of Science:
- Medical informatics
- Infectious diseases
- Geriatric medicine
Background:
- Hospitalizations for serious infections are common in middle-aged and older adults.
- Diagnosis codes are frequently used to identify these hospitalizations in research.
- The performance of diagnosis codes for serious infections in this population is not well-established.
Purpose of the Study:
- To determine the positive predictive value (PPV) of diagnosis codes for identifying hospitalizations due to serious infections.
- To evaluate the accuracy of International Classification of Diseases, Ninth Revision (ICD-9) codes for common serious infections in adults aged 50 and older.
Main Methods:
- Retrospective cohort study of Tennessee Medicaid enrollees (2008-2012).
- Identified hospitalizations using ICD-9 codes for pneumonia, meningitis/encephalitis, bacteremia/sepsis, cellulitis, endocarditis, pyelonephritis, and septic arthritis/osteomyelitis.
- Medical records were reviewed by trained clinicians to confirm infections; PPV was calculated using confirmed hospitalizations as the reference standard.
Main Results:
- The overall PPV of diagnosis codes for hospitalizations for infection was 90.2%.
- PPV was highest for pneumonia (96.5%) and cellulitis (91.1%), and lowest for meningitis/encephalitis (50.0%).
- Adjudication reliability between reviewers was excellent (92.7% agreement).
Conclusions:
- Discharge diagnosis codes demonstrate a high PPV for identifying hospitalizations for common, serious infections in middle-aged and older adults.
- PPV estimates for rare infections were imprecise, suggesting caution in their use for research.
- Diagnosis codes are a valuable tool for identifying serious infections in this demographic, with specific codes showing high accuracy.
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