Development and Assessment of a New Framework for Disease Surveillance, Prediction, and Risk Adjustment: The Diagnostic Items Classification System

Abstract

Importance: Current disease risk-adjustment formulas in the US rely on diagnostic classification frameworks that predate the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM).

Objective: To develop an ICD-10-CM-based classification framework for predicting diverse health care payment, quality, and performance outcomes.

Design setting and participants: Physician teams mapped all ICD-10-CM diagnoses into 3 types of diagnostic items (DXIs): main effect DXIs that specify diseases; modifiers, such as laterality, timing, and acuity; and scaled variables, such as body mass index, gestational age, and birth weight. Every diagnosis was mapped to at least 1 DXI. Stepwise and weighted least-squares estimation predicted cost and utilization outcomes, and their performance was compared with models built on (1) the Agency for Healthcare Research and Quality Clinical Classifications Software Refined (CCSR) categories, and (2) the Health and Human Services Hierarchical Condition Categories (HHS-HCC) used in the Affordable Care Act Marketplace. Each model's performance was validated using R ², mean absolute error, the Cumming prediction measure, and comparisons of actual to predicted outcomes by spending percentiles and by diagnostic frequency. The IBM MarketScan Commercial Claims and Encounters Database, 2016 to 2018, was used, which included privately insured, full- or partial-year eligible enrollees aged 0 to 64 years in plans with medical, drug, and mental health/substance use coverage.

Main outcomes and measures: Fourteen concurrent outcomes were predicted: overall and plan-paid health care spending (top-coded and not top-coded); enrollee out-of-pocket spending; hospital days and admissions; emergency department visits; and spending for 6 types of services. The primary outcome was annual health care spending top-coded at $250 000.

Results: A total of 65 901 460 person-years were split into 90% estimation/10% validation samples (n = 6 604 259). In all, 3223 DXIs were created: 2435 main effects, 772 modifiers, and 16 scaled items. Stepwise regressions predicting annual health care spending (mean [SD], $5821 [$17 653]) selected 76% of the main effect DXIs with no evidence of overfitting. Validated R ² was 0.589 in the DXI model, 0.539 for CCSR, and 0.428 for HHS-HCC. Use of DXIs reduced underpayment for enrollees with rare (1-in-a-million) diagnoses by 83% relative to HHS-HCCs.

Conclusions: In this diagnostic modeling study, the new DXI classification system showed improved predictions over existing diagnostic classification systems for all spending and utilization outcomes considered.

Figure 1.. Examples Illustrating the DXI Classification Structure

AMI indicates acute myocardial infarction; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); CCSR, Clinical Classifications Software Refined v2019.1 (beta version); DXI, diagnostic item; GE, greater than or equal to; HELLP, hemolysis, elevated liver enzyme and low platelet; LT, less than; NSTEMI, non–ST-segment elevation myocardial infarction; STEMI, ST-segment elevation myocardial infarction; WHO, World Health Organization.

Figure 2.. Mean Residuals of Total Spending for 4 Models by Diagnostic Frequency

For the HCC, CCSR, and DXI models, we calculated the residuals from the total spending model at the enrollee-year level and then assigned these residuals to every unique International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis each enrollee had in a year. We then calculated enrollee-weighted mean residuals in the validation sample using the binned frequencies of diagnoses in the full sample, with frequency intervals determined by powers of 10 per million. Plot whiskers correspond to 95% CIs, corrected for clustering at the patient level. CCSR indicates Clinical Classifications Software Refined model; DXI, diagnostic items model; HCC, Hierarchical Condition Category model; OLS, ordinary least squares; SW, stepwise.