Trends in validated cases of fatal and nonfatal stroke, stroke classification, and risk factors in southeastern New England, 1980 to 1991 : data from the Pawtucket Heart Health Program

Temporal trends in the accuracy of hospital diagnostic coding for identifying acute stroke: A population-based study

Introduction

Administrative hospital diagnostic coding data are increasingly being used in identifying incident and prevalent stroke cases, for outcome audit and for 'big data' research. Validity of administrative coding has varied in previous studies, but little is known about the temporal trends of coding accuracy, which could bias analyses.

Patients and methods

Using all incident and recurrent strokes in a population-based cohort (Oxford Vascular Study/OXVASC) with multiple sources of ascertainment as the reference, we determined the temporal trends in sensitivity and positive predictive value of hospital diagnostic codes for identifying acute stroke from 2002 to 2017.

Results

Of 1883 hospitalised strokes, 1341 (71.2%) were correctly identified by coding. Sensitivity of coding improved over time for all strokes (p_trend = 0.005) and for incident cases (p_trend = 0.002). Of 1995 apparent stroke admissions identified by International Classification of Disease-10 stroke codes (I60-I68), 1588 (79.6%) used the stroke-specific codes (I60-I61/I63-I64). Positive predictive value was higher with the use of specific codes (83.2% vs. 69.2% for all codes) and highest if combined with the first admission only (88.5%), particularly during more recent time periods (2014-2017 = 90.3%). Of 2254 OXVASC incident strokes, 833 (37.0%) were not hospitalised. Sensitivity of coding increased over time for non-disabling stroke (p_trend = 0.001), but not for disabling/fatal stroke (p_trend = 0.40).

Conclusions

Although accuracy of hospital diagnostic coding for identifying acute strokes improved over the last 15 years, residual insensitivity supports linkage to other sources in large epidemiological studies. Moreover, differences in the time trends of coding sensitivity in relation to stroke severity might bias studies of trends in stroke outcome if only administrative coding is used.

Diverging trends in the incidence and mortality of stroke during the period 1986—2002: A study from the Stroke register in Kaunas, Lithuania

Aims: The aim of the present study was to explore the longitudinal stroke trends in the middle-aged Lithuanian population. Methods: All stroke events in the studied population were ascertained and validated according to the standardized criteria outlined by the WHO MONICA Project. The study included all patients aged 25 to 64 years who experienced a stroke between 1986 and 2002. Results: A flat trend was observed in both the incidence and the attack rates of stroke among men during the 17-year study period, while among women, the incidence of stroke increased by 1.7%/year, and the attack rates by 2.3%/year. The 28-day case fatality and mortality rates of stroke decreased significantly in both sexes. The decline in case fatality explained 100% of the decline in mortality. Among the types of stroke, cerebral infarction contributed most to the decline in the mortality in men. In women, the mortality from cerebral infarction and intracerebral haemorrhage declined similarly to that from all types of strokes. Conclusions: Findings from our study indicating no positive changes in the incidence of stroke but instead an increase among middle-aged women in Kaunas are disturbing. These results suggest a need for the intensification of appropriate strategies for stroke prevention by the public health officials in Lithuania.

Accuracy of Electronic Health Record Data for Identifying Stroke Cases in Large-Scale Epidemiological Studies: A Systematic Review from the UK Biobank Stroke Outcomes Group

Objective

Long-term follow-up of population-based prospective studies is often achieved through linkages to coded regional or national health care data. Our knowledge of the accuracy of such data is incomplete. To inform methods for identifying stroke cases in UK Biobank (a prospective study of 503,000 UK adults recruited in middle-age), we systematically evaluated the accuracy of these data for stroke and its main pathological types (ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage), determining the optimum codes for case identification.

Methods

We sought studies published from 1990-November 2013, which compared coded data from death certificates, hospital admissions or primary care with a reference standard for stroke or its pathological types. We extracted information on a range of study characteristics and assessed study quality with the Quality Assessment of Diagnostic Studies tool (QUADAS-2). To assess accuracy, we extracted data on positive predictive values (PPV) and—where available—on sensitivity, specificity, and negative predictive values (NPV).

Results

37 of 39 eligible studies assessed accuracy of International Classification of Diseases (ICD)-coded hospital or death certificate data. They varied widely in their settings, methods, reporting, quality, and in the choice and accuracy of codes. Although PPVs for stroke and its pathological types ranged from 6–97%, appropriately selected, stroke-specific codes (rather than broad cerebrovascular codes) consistently produced PPVs >70%, and in several studies >90%. The few studies with data on sensitivity, specificity and NPV showed higher sensitivity of hospital versus death certificate data for stroke, with specificity and NPV consistently >96%. Few studies assessed either primary care data or combinations of data sources.

Conclusions

Particular stroke-specific codes can yield high PPVs (>90%) for stroke/stroke types. Inclusion of primary care data and combining data sources should improve accuracy in large epidemiological studies, but there is limited published information about these strategies.

Validity of Diagnostic Codes for Acute Stroke in Administrative Databases: A Systematic Review

OBJECTIVE

To conduct a systematic review of studies reporting on the validity of International Classification of Diseases (ICD) codes for identifying stroke in administrative data.

METHODS

MEDLINE and EMBASE were searched (inception to February 2015) for studies: (a) Using administrative data to identify stroke; or (b) Evaluating the validity of stroke codes in administrative data; and (c) Reporting validation statistics (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), or Kappa scores) for stroke, or data sufficient for their calculation. Additional articles were located by hand search (up to February 2015) of original papers. Studies solely evaluating codes for transient ischaemic attack were excluded. Data were extracted by two independent reviewers; article quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool.

RESULTS

Seventy-seven studies published from 1976-2015 were included. The sensitivity of ICD-9 430-438/ICD-10 I60-I69 for any cerebrovascular disease was ≥ 82% in most [≥ 50%] studies, and specificity and NPV were both ≥ 95%. The PPV of these codes for any cerebrovascular disease was ≥ 81% in most studies, while the PPV specifically for acute stroke was ≤ 68%. In at least 50% of studies, PPVs were ≥ 93% for subarachnoid haemorrhage (ICD-9 430/ICD-10 I60), 89% for intracerebral haemorrhage (ICD-9 431/ICD-10 I61), and 82% for ischaemic stroke (ICD-9 434/ICD-10 I63 or ICD-9 434&436). For in-hospital deaths, sensitivity was 55%. For cerebrovascular disease or acute stroke as a cause-of-death on death certificates, sensitivity was ≤ 71% in most studies while PPV was ≥ 87%.

CONCLUSIONS

While most cases of prevalent cerebrovascular disease can be detected using 430-438/I60-I69 collectively, acute stroke must be defined using more specific codes. Most in-hospital deaths and death certificates with stroke as a cause-of-death correspond to true stroke deaths. Linking vital statistics and hospitalization data may improve the ascertainment of fatal stroke.

Seven-Year Trends in Stroke Rehabilitation: Patient Characteristics, Medical Complications, and Functional Outcomes

Studies of stroke trends have focused primarily on incidence, mortality, and hospitalization rates. There has been little evaluation of changes over time in the common patient characteristics, medical comorbidities, and functional outcomes of patients. The present study evaluated changes during a 7-year period. We found that while demographic variables, stroke severity, and most stroke characteristics remained relatively stable, disability levels at admission and discharge decreased and frequencies of both medical tube usage and many secondary medical complications increased over time. These changes have important implications for the clinical management of stroke patients in rehabilitation and for the organization and financing of stroke rehabilitation programs.

Validity of international classification of disease codes to identify ischemic stroke and intracranial hemorrhage among individuals with associated diagnosis of atrial fibrillation

BACKGROUND

Because of its association with death and disability, stroke is a focus of outcomes in atrial fibrillation (AF) research. International Classification of Disease-Ninth Revision (ICD-9) edition codes are commonly used to identify stroke in research, particularly in large administrative data. We sought to assess the validity of ICD-9 codes in stroke case ascertainment and for AF across 3 institutions.

METHODS AND RESULTS

Participating centers included Boston Medical Center (safety net hospital), Geisinger Health System (rural Pennsylvania), and the University of Alabama (academic center in the southeastern stroke belt). ICD-9 codes for ischemic stroke (433-434, 436) and intracranial hemorrhage (430-432) identified 1812 stroke cases with an associated code for AF (427.31) from 2006 to 2010. Cases were vetted through chart review with final adjudication by a stroke neurologist. Review considered 94.2% of ICD-9 identified stroke cases valid with decreased accuracy for concurrent AF diagnosis (82.28%) and stroke attributable to AF (72.8%). Among events with "without infarction" modifiers, 7.2% were valid strokes. ICD-9 stroke code accuracy did not differ by stroke type or site. Stroke code 434 displayed higher accuracy than 433 (94.4% versus 85.2%; P<0.01), and primary stroke codes were more accurate than nonprimary codes (97.2% versus 83.7%; P<0.0001).

CONCLUSIONS

Using ICD-9 stroke and AF codes to identify patients with stroke plus AF resulted in inaccuracies. Given the expanded financial and policy implications of patient-oriented research, conclusions derived solely from administrative data without validation of outcome events should be interpreted with caution.

Validity of hospital discharge diagnosis codes for stroke: the Atherosclerosis Risk in Communities Study

BACKGROUND AND PURPOSE

Characterizing International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) code validity is essential given widespread use of hospital discharge databases in research. Using the Atherosclerosis Risk in Communities (ARIC) Study, we estimated the accuracy of ICD-9-CM stroke codes.

METHODS

Hospitalizations with ICD-9-CM codes 430 to 438 or stroke keywords in the discharge summary were abstracted for ARIC cohort members (1987-2010). A computer algorithm and physician reviewer classified definite and probable ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Using ARIC classification as a gold standard, we calculated the positive predictive value (PPV) and sensitivity of ICD-9-CM codes grouped according to the American Heart Association/American Stroke Association (AHA/ASA) 2013 categories and an alternative code grouping for comparison.

RESULTS

Thirty-three percent of 4260 hospitalizations were validated as strokes (1251 ischemic, 120 intracerebral hemorrhage, 46 subarachnoid hemorrhage). The AHA/ASA code groups had PPV 76% and 68% sensitivity compared with PPV 72% and 83% sensitivity for the alternative code groups. The PPV of the AHA/ASA code group for ischemic stroke was slightly higher among blacks, individuals <65 years, and at teaching hospitals. Sensitivity was higher among older individuals and increased over time. The PPV of the AHA/ASA code group for intracerebral hemorrhage was higher among blacks, women, and younger individuals. PPV and sensitivity varied across study sites.

CONCLUSIONS

A new AHA/ASA discharge code grouping to identify stroke had similar PPV and lower sensitivity compared with an alternative code grouping. Accuracy varied by patient characteristics and study sites.

Validity of claims-based stroke algorithms in contemporary Medicare data: reasons for geographic and racial differences in stroke (REGARDS) study linked with medicare claims

BACKGROUND

The accuracy of stroke diagnosis in administrative claims for a contemporary population of Medicare enrollees has not been studied. We assessed the validity of diagnostic coding algorithms for identifying stroke in the Medicare population by linking data from the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study to Medicare claims.

METHODS AND RESULTS

The REGARDS Study enrolled 30 239 participants ≥45 years in the United States between 2003 and 2007. Stroke experts adjudicated suspected strokes, using retrieved medical records. We linked data for participants enrolled in fee-for-service Medicare to claims files from 2003 through 2009. Using adjudicated strokes as the gold standard, we calculated accuracy measures for algorithms to identify incident and recurrent strokes. We linked data for 15 089 participants, among whom 422 participants had adjudicated strokes during follow-up. An algorithm using primary discharge diagnosis codes for acute ischemic or hemorrhagic stroke (International Classification of Diseases, Ninth Revision, Clinical Modification codes: 430, 431, 433.x1, 434.x1, 436) had a positive predictive value of 92.6% (95% confidence interval, 88.8%-96.4%), a specificity of 99.8% (99.6%-99.9%), and a sensitivity of 59.5% (53.8%-65.1%). An algorithm using only acute ischemic stroke codes (433.x1, 434.x1, 436) had a positive predictive value of 91.1% (95% confidence interval, 86.6%-95.5%), a specificity of 99.8% (99.7%-99.9%), and a sensitivity of 58.6% (52.4%-64.7%).

CONCLUSIONS

Claims-based algorithms to identify stroke in a contemporary Medicare cohort had high positive predictive value and specificity, supporting their use as outcomes for etiologic and comparative effectiveness studies in similar populations. These inpatient algorithms are unsuitable for estimating stroke incidence because of low sensitivity.

Commentary: approaches, strengths, and limitations of avoidable mortality

Publication of recent papers such as the one by Schoenbaum and colleagues entitled 'Mortality Amenable to Health Care in the United States: The Roles of Demographics and Health Systems Performance' has stimulated this commentary. We discuss strengths and limitations of amenable and avoidable mortality in health-care systems' performance and their contribution to health inequalities. To illustrate, we present a case study of avoidable and amenable mortality in Spain over 27 years. We conclude that amenable mortality is not a good indicator of health-care systems' performance, or for determining whether it could give rise to health inequalities. To understand health problems and to assess the impact of interventions affecting health requires good, basic, and routine monitoring of health indicators and of socioeconomic determinants of health.

Predictors of early mortality in patients with ischemic stroke

Accurate predictors of early outcome in stroke patients have a number of important applications, such as introducing secondary prevention strategies, supporting treatment decisions or designing randomized clinical trials. Surprisingly, a generally accepted, reliable and well-validated mortality-prediction model is still unavailable. This review outlines the most important predictors of in-hospital mortality that could be assessed at admission to hospital emergency room within 24 h of ischemic stroke onset. A number of factors are discussed such as nonmodifiable factors (e.g., age, gender and genetic factors); type of stroke and its severity - measured by different clinical score scales; predictive models; laboratory markers; special neuroradiological and neurophysiological tests; and comorbid conditions at admission and quality of hospital care.

Validity of discharge diagnoses in the surveillance of stroke

BACKGROUND

Hospital administrative data have been suggested as a valuable cost-effective tool for providing information about the stroke burden. Nevertheless, the choice of the diagnosis codes has been a critical issue in the development of case ascertainment algorithms.

METHODS

In this study, the Minimum Basic Data Set administrative database was used to analyze the accuracy of different ICD-9-CM algorithms based on the neurologist's clinical judgement as the 'gold standard'.

RESULTS

The most accurate algorithm observed in our study involved the selection of ICD-9-CM codes 430-438 in the primary diagnosis. It yielded a sensitivity of 96.1%, a specificity of 87.5% and a positive predictive value of 82.5%.

CONCLUSIONS

The Minimum Basic Data Set is a valuable source to evaluate stroke frequency when using an accurate algorithm to select events.

A systematic review of validated methods for identifying cerebrovascular accident or transient ischemic attack using administrative data

PURPOSE

To perform a systematic review of the validity of algorithms for identifying cerebrovascular accidents (CVAs) or transient ischemic attacks (TIAs) using administrative and claims data.

METHODS

PubMed and Iowa Drug Information Service searches of the English language literature were performed to identify studies published between 1990 and 2010 that evaluated the validity of algorithms for identifying CVAs (ischemic and hemorrhagic strokes, intracranial hemorrhage, and subarachnoid hemorrhage) and/or TIAs in administrative data. Two study investigators independently reviewed the abstracts and articles to determine relevant studies according to pre-specified criteria.

RESULTS

A total of 35 articles met the criteria for evaluation. Of these, 26 articles provided data to evaluate the validity of stroke, seven reported the validity of TIA, five reported the validity of intracranial bleeds (intracerebral hemorrhage and subarachnoid hemorrhage), and 10 studies reported the validity of algorithms to identify the composite endpoints of stroke/TIA or cerebrovascular disease. Positive predictive values (PPVs) varied depending on the specific outcomes and algorithms evaluated. Specific algorithms to evaluate the presence of stroke and intracranial bleeds were found to have high PPVs (80% or greater). Algorithms to evaluate TIAs in adult populations were generally found to have PPVs of 70% or greater.

CONCLUSIONS

The algorithms and definitions to identify CVAs and TIAs using administrative and claims data differ greatly in the published literature. The choice of the algorithm employed should be determined by the stroke subtype of interest.

Combination polypharmacy for cardiovascular disease prevention in men: a decision analysis and cost-effectiveness model

Pharmacotherapies to lower blood pressure and cholesterol are effective in the primary prevention of cardiovascular disease (CVD). The use of fixed-dose medication combinations has not been well studied. The authors created a Markov model to analyze the cost-effectiveness of 4 fixed-dose medications for primary CVD prevention in men. The initial decision node was to treat or not treat men older than 55 years, without CVD, hypertension, or dyslipidemia with a combination of simvastatin, captopril, hydrochlorothiazide, and atenolol. Probability, costs, and effectiveness were derived from the literature. The outcome variable was marginal cost per quality-adjusted life-year (QALY). Sensitivity analyses were performed. The average cost of treatment was $70,000 compared with $93,000 for non-treatment. Treatment resulted in 13.62 QALYs vs 12.96 QALYs without treatment. Primary prevention of CVD with fixed-dose medications dominated "no-treatment." The use of a fixed-dose polypharmacy approach to CVD prevention in men older than 55 years may be cost-effective.

Cohort-specific trends in stroke mortality in seven European countries were related to infant mortality rates

OBJECTIVES

To assess, in a population-based study, whether secular trends in cardiovascular disease mortality in seven European countries were correlated with past trends in infant mortality rate (IMR) in these countries.

STUDY DESIGN AND SETTING

Data on ischemic heart disease (IHD) and stroke mortality in 1950-1999 in the Netherlands, England & Wales, France, and four Nordic countries were analyzed. We used Poisson regression to describe trends in mortality according to birth cohort, for the cohorts born between 1860 and 1939. Pearson correlation coefficients were calculated to determine associations between IMR and IHD, or stroke mortality.

RESULTS

IHD mortality increased for successive cohorts up to 1900, and then started to decline. Stroke mortality levels were virtually stable among birth cohorts up to 1880, but declined rapidly among later cohorts. A strong positive association was found between cohort-specific IMR levels and stroke mortality rates. There were no strong cohort-wise associations between IMR and IHD mortality.

CONCLUSION

These results support other studies in suggesting that living conditions in early childhood may influence population levels of stroke mortality. Future studies should determine the contribution of specific early life factors to the mortality decline in IHD and especially stroke.

The impact of ageing on stroke subtypes, length of stay and mortality: study in the province of Teruel, Spain

BACKGROUND AND PURPOSE

During the last three decades, there have been important advances in the diagnosis and treatment of stroke leading to a decline in mortality rates in western countries. However, the longer life expectancy and the higher proportion of elderly people in the structure of the population may partially counteract this positive trend in stroke-related mortality. The purpose of this study was to analyse the impact of a high ageing index of the population on stroke-related variables such as stroke subtypes, length of hospital stay and mortality from stroke.

METHODS

We analysed the data of 1850 consecutive patients with first-ever stroke retrieved from a prospective registry over a period of 8 years (1994-2001) in the province of Teruel, Spain, with two public hospitals in the catchment area. The mean age was 75.5 years (SD: 9.4) and the sex was male in 62% of cases. The variables included in the study were vascular risk factors, stroke subtypes, fatality rate, length of stay and mortality. Mortality was assessed from 1990 to 2000.

RESULTS

Arterial hypertension and atrial fibrillation were the most frequent risk factors, with an observed high frequency of cardioembolic stroke. The mean 28-day case fatality rate was 16.6%, ranging from 11.9% in 1994 to 23.4% in 1999. We found complications in 38% of patients, especially in the elderly. Fatality occurred in 20.3% of elderly subjects (65 or over) in comparison to 7.25% for those younger (Relative risk: 2.8; 95% CI: 1.475.3). Crude mortality rates were higher than for the general population in Spain and ranged from 169 in 1991 to 139/100,000 in 2000 with higher rates for women. However, the age-adjusted mortality rate to the standard European population was 56.6/100,000 (95% CI: 4664) in 1999, which was similar to that found in Spain (61/100,000).

CONCLUSIONS

The impact of ageing on case fatality and mortality by stroke was substantial. Whereas mortality by stroke stabilized after decreasing in our province and in Spain in the last decade, fatality rates have significantly increased in our province because of the high proportion of elderly people and to the high rate of post-stroke complications.