{"id":46662,"date":"2015-01-22T06:32:41","date_gmt":"2015-01-22T11:32:41","guid":{"rendered":"http:\/\/blogs.nejm.org\/cardioexchange\/?post_type=voices&p=46662"},"modified":"2015-01-22T06:34:17","modified_gmt":"2015-01-22T11:34:17","slug":"how-accurately-do-icd-9-codes-identify-strokes-in-patients-with-atrial-fibrillation","status":"publish","type":"post","link":"https:\/\/blogs.nejm.org\/cardioexchange\/2015\/01\/22\/how-accurately-do-icd-9-codes-identify-strokes-in-patients-with-atrial-fibrillation\/","title":{"rendered":"How Accurately Do ICD-9 Codes Identify Strokes in Patients with Atrial Fibrillation?"},"content":{"rendered":"

The CardioExchange Editors<\/b> interview Jonathan L. Thigpen<\/b> about his research group\u2019s assessment of the validity of ICD-9 codes in identifying strokes in patients with atrial fibrillation. <\/i>The article is published in<\/i> Circulation: Cardiovascular Quality and Outcomes.<\/i><\/a><\/i><\/p>\n

CardioExchange Editors:<\/i><\/b> Please describe what you studied and what you found.<\/b><\/p>\n

Thigpen:<\/i><\/b> We assessed the accuracy of International Classification of Disease, 9th edition (ICD-9) stroke codes in identifying valid stroke events in a cohort of atrial fibrillation (AF) patients. The initial electronic search yielded 1812 events across three stroke centers (Boston Medical Center, Geisinger Health System, and the University of Alabama). All ICD-9\u2013identified stroke events were vetted through\u00a0manual chart review with final adjudication by\u00a0a stroke neurologist. AF was verified by electrocardiographic evidence at the stroke admission, 6 months before the admission, or 90 days after the admission.<\/p>\n

In addition to assessing the accuracy of the stroke codes alone, we also assessed the combined accuracy of stroke and AF codes, as well as the accuracy of stroke codes in identifying stroke that was associated with AF. These additional steps offer insight about the accuracy and reliability of using only ICD-9 codes to create a \u201cstroke plus AF\u201d cohort. This effort is extremely important given the increasing reliance\u00a0on ICD-9 codes to identify stroke events and\u00a0covariates in research, especially research that uses administrative data.<\/p>\n

The\u00a0positive predictive value (PPV) of stroke codes alone was 94.2%.\u00a0PPVs did not differ across clinical site or by type of event\u00a0(ischemic vs. intracranial hemorrhage), but they did differ by event-coding position (primary vs. other; 97.2% vs. 83.7%)\u00a0and by ischemic stroke code (433 vs. 434; 85.2% vs. 94.4%).\u00a0When combined with validation of AF codes, the PPV of stroke codes dropped to 82.2%. After we excluded ischemic stroke that was caused by\u00a0a different mechanism (e.g., a vascular procedure, tumor, sepsis), the PPV dropped further to 72.8%. As a separate exercise,\u00a0manual review confirmed\u00a033 (7.2%) ischemic strokes in 458\u00a0events coded as \u201cwithout infarction.\u201d<\/p>\n

Editors:<\/i><\/b> What are the implications for published papers that have used claims data?<\/b><\/p>\n

Thigpen:<\/i><\/b> <\/b>Our results indicate that ICD-9 stroke codes alone have limited use in identifying\u00a0acute strokes in patients with active AF. We suggest that, to limit potential bias, manual verification of stroke\u00a0is needed to confirm stroke events in the setting of AF.<\/p>\n

We recognize that\u00a0a screening method with a PPV \u226585% (as has been previously suggested) may be\u00a0adequate for research purposes and is likely to bias estimates very little. However, this thinking rationalizes\u00a0inaccuracies, which may not be acceptable to some observers.\u00a0Results derived from\u00a0screening methods with\u00a0PPVs <85%\u00a0are likely to have minimal value. For example, a stroke research study implementing a screening method with a PPV of 80% would mean that 20% of the\u00a0patients\u00a0identified as having stroke were in fact false positives, likely leading to significant bias in results.<\/p>\n

In any paper that uses ICD-9 screening methods, readers must critically assess the\u00a0given PPV of the ICD-9 codes and identify the specific screening methods employed (i.e., only including\u00a0strokes coded in the\u00a0primary position). The latter is especially important\u00a0considering that many studies do not report ICD-9 accuracies.<\/p>\n

Editors:<\/i><\/b> Do particular studies concern you? Might their results have been different with more-accurate data on outcomes?\u00a0<\/b><\/p>\n

Thigpen:<\/i><\/b> Concerns should be raised about any study that withholds information regarding the accuracy of ICD-9 stroke codes used for case ascertainment. This is especially true if\u00a0methods to increase accuracies of ICD-9 screening procedures are not implemented (our study reports several\u00a0available methods, confirmed in previous literature).\u00a0Without being given the ICD-9 accuracy data for a given study, readers must assume that there are false positives in the cohort, thereby leading to bias (the extent of the false positives and resulting bias may be hard to determine).\u00a0In recognizing the varying accuracies of ICD-9 stroke codes, we suggest (as many researchers employ) additional screening methods (i.e., manual verification) to increase accuracy.<\/p>\n

Increasing the accuracy of\u00a0ICD-9 stroke codes in the setting of AF\u00a0will have a variable effect on a study\u2019s results depending\u00a0on several factors, including (but not limited to) the degree of the increase in\u00a0accuracy,\u00a0how the codes were used (to identify patients vs.\u00a0to ascertain outcomes), and the investigators\u2019 initial conclusions.<\/p>\n

Editors:<\/i><\/b> Do you think that ICD-10 will be better?<\/b><\/p>\n

Thigpen:<\/i><\/b> We know little about the\u00a0accuracy of\u00a0ICD-10 stroke codes.\u00a0Current evidence indicates that the accuracy is similar to that of ICD-9 codes, although\u00a0ICD-10\u00a0codes are thought to be\u00a0more specific and provide a more intuitive coding method. For example, ICD-10\u00a0codes specify the hemorrhage location and source in intracranial hemorrhage, distinguish between thrombotic and embolic ischemic stroke, and include codes for intraoperative and postprocedural strokes. However, we suggest that until ICD-10\u00a0stroke codes\u2019 accuracies are further pinpointed and compared with those of ICD-9 <\/i>stroke codes, manual review\u00a0of events\u00a0seems to be warranted.<\/p>\n

JOIN THE DISCUSSION<\/b><\/p>\n

Do Jonathan Thigpen\u2019s findings affect your degree of trust in how well ICD-9 codes identify strokes in patients with atrial fibrillation?<\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

Jonathan L. Thigpen discusses his research group\u2019s assessment of the validity of ICD-9 codes in identifying strokes in patients with atrial fibrillation.<\/p>\n","protected":false},"author":1003,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[341,2473,253],"class_list":["post-46662","post","type-post","status-publish","format-standard","hentry","category-electrophysiology","tag-atrial-fibrillation","tag-icd-9-codes","tag-stroke"],"_links":{"self":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts\/46662","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/users\/1003"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/comments?post=46662"}],"version-history":[{"count":0,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/posts\/46662\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/media?parent=46662"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/categories?post=46662"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nejm.org\/cardioexchange\/wp-json\/wp\/v2\/tags?post=46662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}