Comparison of Medicare claims-based Clostridioides difficile infection epidemiologic case classification algorithms to medical record review by the Emerging Infections Program using a linked cohort, 2016-2021

Abstract

Background: Medicare claims are frequently used to study Clostridioides difficile infection (CDI) epidemiology. However, they lack specimen collection and diagnosis dates to assign location of onset. Algorithms to classify CDI onset location using claims data have been published, but the degree of misclassification is unknown.

Methods: We linked patients with laboratory-confirmed CDI reported to four Emerging Infections Program (EIP) sites from 2016-2021 to Medicare beneficiaries with fee-for-service Part A/B coverage. We calculated sensitivity of ICD-10-CM codes in claims within ±28 days of EIP specimen collection. CDI was categorized as hospital, long-term care facility, or community-onset using three different Medicare claims-based algorithms based on claim type, ICD-10-CM code position, duration of hospitalization, and ICD-10-CM diagnosis code presence-on-admission indicators. We assessed concordance of EIP case classifications, based on chart review and specimen collection date, with claims case classifications using Cohen's kappa statistic.

Results: Of 12,671 CDI cases eligible for linkage, 9,032 (71%) were linked to a single, unique Medicare beneficiary. Compared to EIP, sensitivity of CDI ICD-10-CM codes was 81%; codes were more likely to be present for hospitalized patients (93.0%) than those who were not (56.2%). Concordance between EIP and Medicare claims algorithms ranged from 68% to 75%, depending on the algorithm used (κ = 0.56-0.66).

Conclusion: ICD-10-CM codes in Medicare claims data had high sensitivity compared to laboratory-confirmed CDI reported to EIP. Claims-based epidemiologic classification algorithms had moderate concordance with EIP classification of onset location. Misclassification of CDI onset location using Medicare algorithms may bias findings of claims-based CDI studies.

Figure 1.

Flowchart depicting study sample after applying inclusion criteria, 4 Emerging Infections Program Sites, 2016–2021. *Coverage criteria include Medicare beneficiaries ages 65 and up with both Part A and Part B fee-for-service (A/B FFS) coverage in the month before through the month after stool collection that tested positive for Clostridiodes difficile infection.

Figure 2.

Medicare beneficiary linkage outcome* by Year (2a) and Emerging Infections Program (EIP) C. difficile infection epidemiologic classification (2b), 4 EIP Sites, 2016–2021. *A linkage outcome of unique represents a single unique Medicare beneficiary being linked to the EIP case patient. Linkage outcomes of multiple represent EIP case-patients with multiple potential Medicare beneficiaries, and outcomes of none represent EIP case-patients with no potential Medicare beneficiaries using the linkage criteria described.

Figure 3.

Clostridiodes difficile infection (CDI) onset classification using Emerging Infections Program (EIP, left) and claims-based definitions (right). Figure 3a) Algorithm 1, 3b) Algorithm 2, 3c) Algorithm 3. Definitions for EIP as well as each claims-based algorithm provided in Table 1. CDI onset is classified as community-onset (CO), hospital-onset (HO), or long-term care facility onset (LTCFO).