Background Administrative data are frequently used in stroke research. Ensuring accurate identification of patients who had an ischaemic stroke, and those receiving thrombolysis and endovascular thrombectomy (EVT) is critical to ensure representativeness and generalisability. We examined differences in patient samples based on mode of identification, and propose a strategy for future patient and procedure identification in large administrative databases.
Methods We used non-public administrative data from the state of California to identify all patients who had an ischaemic stroke discharged from an emergency department (ED) or inpatient hospitalisation from 2010 to 2017 based on International Classification of Disease (ICD-9) (2010–2015), ICD-10 (2015–2017) and Medicare Severity-Diagnosis-related Group (MS-DRG) discharge codes. We identified patients with interhospital transfers, patients receiving thrombolytics and patients treated with EVT based on ICD, Current Procedural Terminology (CPT) and MS-DRG codes. We determined what proportion of these transfers and procedures would have been identified with ICD versus MS-DRG discharge codes.
Results Of 365 099 ischaemic stroke encounters, most (87.70%) had both a stroke-related ICD-9 or ICD-10 code and stroke-related MS-DRG code; 12.28% had only an ICD-9 or ICD-10 code and 0.02% had only an MS-DRG code. Nearly all transfers (99.99%) were identified using ICD codes. We identified 32 433 thrombolytic-treated patients (8.9% of total) using ICD, CPT and MS-DRG codes; the combination of ICD and CPT codes identified nearly all (98%). We identified 7691 patients treated with EVT (2.1% of total) using ICD and MS-DRG codes; both MS-DRG and ICD-9/ICD-10 codes were necessary because ICD codes alone missed 13.2% of EVTs. CPT codes only pertain to outpatient/ED patients and are not useful for EVT identification.
Conclusions ICD-9/ICD-10 diagnosis codes capture nearly all ischaemic stroke encounters and transfers, while the combination of ICD-9/ICD-10 and CPT codes are adequate for identifying thrombolytic treatment in administrative datasets. However, MS-DRG codes are necessary in addition to ICD codes for identifying EVT, likely due to favourable reimbursement for EVT-related MS-DRG codes incentivising accurate coding.
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Contributors KSZ and RYH conceived the study; KSZ, SL, LHS and RYH designed the analysis; SL and KSZ performed the analysis. All authors contributed to interpretation and presentation of the results, and critical revisions of the manuscript.
Funding Agency for Healthcare Research and Quality (PI Zachrison, K08HS024561); National Institutes of Health (PI Hsia R01HL134182, R01HL114822).
Competing interests OA reports Founder and Equity Holder, Sense Diagnostics. LHS reports the following relationships relevant to research grants or companies that manufacture products for thrombolysis or thrombectomy even if interactions involve non-thrombolysis products: scientific consultant regarding trial design and conduct to Genentech (late window thrombolysis) and Member of steering committee (TIMELESS NCT03785678); user interface design and usability to LifeImage (privately held company); stroke systems of care consultant to the Massachusetts Dept of Public Health; member of a Data Safety Monitoring Board (DSMB) for Penumbra (MIND NCT03342664); Diffusion Pharma PHAST-TSC NCT03763929); National PI or member of National Steering Committee for Medtronic (Stroke AF NCT02700945, CURRENT); PI, late window thrombolysis trial, NINDS (P50NS0515343, MR WITNESS NCT01282242); PI, StrokeNet Network NINDS (New England Regional Coordinating Center U24NS107243).
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available. This study used non-public data maintained by the California Office of Statewide Health Planning and Development. All data requests should be made directly to this organisation.
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