- Email: [email protected]
People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy, and generalized nonconvulsive epilepsy—US MarketScan data, 2010–2015
YEBEH-05565; No of Pages 3 Epilepsy & Behavior xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Epilepsy & Behavior journal homepage: www.elsevier.com/locate/yebeh
Epilepsy by the Numbers — from the US Centers for Disease Control and Prevention
People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy, and generalized nonconvulsive epilepsy—US MarketScan data, 2010–2015☆ Sanjeeb Sapkota a,⁎, Rosemarie Kobau b, Daniel M. Pastula b,c, Matthew M. Zack b a G2S Corporation, Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (CDC), Mail Stop F-78, 4770 Buford Hwy, 30341 GA, United States b Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, CDC, Mail Stop F-78, 4770 Buford Hwy, 30341 GA, United States c University of Colorado, School of Medicine and Colorado School of Public Health, Aurora, Colorado, United States
a r t i c l e
i n f o
Article history: Received 30 October 2017 Accepted 1 November 2017 Available online xxxx
a b s t r a c t The distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria. No recent US study has examined the distribution of epilepsy types in a large, population-based sample of people with epilepsy. We used MarketScan data from January 1, 2010 through September 30, 2015, to estimate the proportion of epilepsy types among all (N = 370,570) individuals diagnosed with epilepsy. We identified cases of epilepsy as individuals with at least one International Classification of Disease, 9th version (ICD-9) diagnostic code of 345.X and the use of at least one antiseizure drug described in the 2015 MarketScan Redbook. Unspecified epilepsy was more common (36.8%) than focal-localized epilepsy (24.6%), generalized convulsive epilepsy (23.8%), generalized nonconvulsive epilepsy (8.9%), other forms of epilepsy (5.2%), infantile spasm (0.3%), and epilepsia partialis continua (0.3%). The high proportion of epilepsy classified as unspecified might be lowered by improved training in epilepsy diagnosis and coding. © 2017 Elsevier Inc. All rights reserved.
1. Introduction People tend to think primarily of generalized convulsive seizures when considering epilepsy [1], but many are unaware of the different types of nonmotor and focal-onset seizures that have more nuanced signs and symptoms. This lack of awareness has multiple implications for public awareness efforts for education, symptom awareness, seizure first-aid, and stigma reduction. The reported distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria (e.g., classification guidelines; incident vs. prevalent cases; dominant seizure vs. all seizure types assessed) [2]. Among incident cases of epilepsy in Rochester, Minnesota (1935–1984), only 23% had generalized tonic–clonic seizures; about 57% had focal (formerly known as partial) seizures, and the rest had other generalized or unknown types [3]. This classic Rochester study, based on data from ☆ Disclaimer: The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. ⁎ Corresponding author at: G2S Corporation, Mail Stop F-78, Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (CDC), 4770 Buford Hwy, 30341 GA, United States. E-mail address: [email protected] (S. Sapkota).
1935 to 1984, often serves as a key reference for the distribution of seizure types among the US population [3]. Some international studies of clinical samples support a similar distribution of seizure types among classifiable epilepsies, with focal seizures being somewhat more common than generalized seizures [4,5]. But, in their review, Banerjee and colleagues [2] found nearly equal distributions of focal and generalized seizure types among clinical and population-based studies. These discrepancies depend on sample characteristics, different classification guidelines used by investigators, diagnostic limitations, case ascertainment criteria, and other methodological factors [2,4]. Our study uses a sample of US administrative claims data to examine the proportions of epilepsy types, to understand likely corresponding seizure types [3] among people with epilepsy of all ages. To our knowledge, no recent US study has examined the distribution of epilepsy types among a large, population-based sample of people with epilepsy. 2. Methods We used the Truven Health Analytics, Inc. MarketScan Commercial Claims and Encounters and Medicare Supplemental Database from across the United States, and the MarketScan Medicaid Multi-State Database representing 13 states [6]. In addition, we used MarketScan's
https://doi.org/10.1016/j.yebeh.2017.11.004 1525-5050/© 2017 Elsevier Inc. All rights reserved.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004
2
S. Sapkota et al. / Epilepsy & Behavior xxx (2017) xxx–xxx
statistical software, Treatment Pathways, to analyze the data set from January 1, 2010 through September 30, 2015. We defined cases of epilepsy as individuals with a claim that included at least one International Classification of Disease, 9th Revision (ICD-9) specific diagnostic code of 345.X and the use of at least one antiseizure drug from the 2015 MarketScan Redbook. We used the following codes: 345.0 (generalized nonconvulsive epilepsy); 345.1 (generalized convulsive epilepsy); 345.4 (localization-related [focal] [partial] epilepsy and epileptic syndromes with complex partial seizures); and 345.5 (localization-related [focal] [partial] epilepsy and epileptic syndromes with simple partial seizures); 345.6 (infantile spasms); 345.7 (epilepsia partialis continua, or recurrent focal motor seizures); 345.8 (other forms of epilepsy and recurrent seizures, such as anoxic epileptic seizure, benign occipital epilepsy of childhood—early onset variant, or benign Rolandic epilepsy); and 345.9 (epilepsy, unspecified). Because antiseizure drugs are typically prescribed for epilepsy and not for transient provoked seizures, requiring at least one prescription in our case definition adds to the specificity of the epilepsy diagnosis. We stratified seizure type among epilepsy cases by all ages and by children aged 0–17 years. We excluded two types of seizures classified with ICD-9 codes, 780.33 (posttraumatic seizure) and 780.39 (other seizure), because not all seizures in these categories are true epilepsy. We also excluded another two types of status epilepticus classified with ICD-9 codes, 345.3 (grand mal status) and 345.2 (petit mal status), because either code may be associated with various types of epilepsy, and because neither of them specifies a particular epilepsy type. Our epilepsy classification resembles that of Helmers and colleagues [7], except for excluding the above mentioned four types of epilepsy (i.e., 780.33, 780.39, 345.2, and 345.3). 3. Results The 2010–2015 MarketScan data included 78,489,988 individuals, of whom 370,570 (0.47%) were classified as having epilepsy, according to our case definition. These latter individuals represent prevalent cases of epilepsy between January 1, 2010 and September 30, 2015. Thirty percent of cases had two or more different epilepsy types assigned at different times. The most frequently occurring epilepsy type was unspecified epilepsy (ICD-9 code, 345.9 [n = 136,350 cases; 36.8%]) (Fig. 1), followed by localization-related focal epilepsy (ICD-9 codes
345.4 and 345.5 [n = 91,084 cases; 24.6%]); generalized convulsive epilepsy (ICD-9 code, 345.1 [n = 88,475 cases; 23.8%]); generalized nonconvulsive epilepsy (ICD-9 code, 345.0 [8.9%]); other forms of epilepsy (ICD-9 code, 345.8 [5.2%]); infantile spasms (ICD-9 code, 345.6 [0.3%]), and epilepsia partialis continua (ICD-9 code, 345.7 [0.3%]). Children with epilepsy showed the similar pattern of epilepsy types (Supplement).
4. Discussion Among all epilepsy types assessed in a large US sample of persons with epilepsy from the MarketScan data, unspecified epilepsy was the most common. Localized or focal epilepsy was the next most common epilepsy type, found among approximately one in four persons with epilepsy, as previously reported [3]. The percentage of cases with generalized convulsive epilepsy was smaller than focal or localized epilepsy. Of all cases of epilepsy, about 30% had a different epilepsy type assigned at different times. It is common for people with epilepsy to have more than one type of seizure and, therefore, be classified with more than one epilepsy type. It is also possible that both the preliminary diagnosis and the confirmed diagnosis for a case are retained in the data, or different physicians assigned the same patient different epilepsy types. In their examination of procedure codes by epilepsy diagnoses, Wilner and colleagues [8] found up to 16% of cases with unspecified epilepsy. The higher proportion in our study might be caused by medical chart coding limitations, insufficient diagnostic capacity among providers, early diagnoses before the diagnostic work-up was complete, or other factors. This suggests a need for improved provider education and coder training in epilepsy classification. Widespread dissemination of the new 2017 International League against Epilepsy guidelines on seizure classification among general and specialty providers and training for medical abstractors might facilitate appropriate epilepsy diagnosis and improved epilepsy classification [9]. The Centers for Disease Control and Prevention (CDC)-supported 2016 Epilepsy Foundation campaign, #ShareMySeizure, is designed to raise the US public's awareness of focal seizures, minimize stigma, and educate the public about appropriate seizure first-aid [10]. Although evaluation of this campaign is forthcoming, given how common focal
40 35 30
Percentages
25 20 15 10 5 0 Unspecified (ICD 9 Focal-Localized Generalized Generalized non- Other Form (ICD 9 Infanle Spasm Epilespia Paralis Code 345.9) (ICD 9 Codes Convulsive (ICD 9 convulsive (ICD 9 Code 345.8) (ICD 9 Code 345.6) Connua (ICD 9 345.4 and 345.5) Code 345.1) Code 345.0) Code 345.7) Types of Epilepsy
Fig. 1. Percentages of epilepsy types among people with epilepsy, MarketScan Data, United States, 2010–2015.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004
S. Sapkota et al. / Epilepsy & Behavior xxx (2017) xxx–xxx
seizures are, additional efforts to increase awareness of focal seizure symptoms may be warranted. This study has several limitations. First, the use of administrative claims data excludes 9% of US individuals without healthcare insurance, who may have a different distribution of epilepsy types. Second, since the quality of epilepsy diagnosis and classification in these data is unknown, some misclassification is likely. Third, the different durations of follow-up for cases in this study implies that some cases were more likely than other cases to have had a single, confirmed diagnosis over the course of a diagnostic workup. Fourth, 30% of the patients had multiple epilepsy types coded during the study period; this inflated our denominator of total epilepsy cases. However, our aim was not to limit cases to those with only one epilepsy type. Finally, the lower prevalence of epilepsy in our study (0.47%) than those in other studies based on MarketScan data, such as Kim and colleagues (0.68% in pediatric population) [11] and Helmers and colleagues (0.85% for all ages) [7], comes partly from our exclusion of 780.3x series of ICD-9 codes for epilepsy cases. Both ICD-9 codes, 780.33 (posttraumatic seizure) and 780.39 (other convulsions), are nonspecific and include a high proportion of provoked seizures. If they were not excluded, then the prevalence would be 0.5% among the pediatric population and 0.7% among the adult population. Findings from our study highlight the need to improve provider education and coder training for classifying epilepsy types. Researchers should continue to examine and refine claims data to enhance their knowledge about the effects of epilepsy, as well as to evaluate programs and care. Supplementary data to this article can be found online at https://doi. org/10.1016/j.yebeh.2017.11.004.
3
Conflict of interest The authors have no conflict of interest to report.
References [1] McNeil K, Brna PM, Gordon KE. Epilepsy in the twitter era: a need to re-tweet the way we think about seizures. Epilepsy Behav 2012;23:127–30. [2] Banerjee PN, Filippi D, Hauser WA. The descriptive epidemiology of epilepsy—a review. Epilepsy Res 2009;85:31–45. [3] Hauser WA, Anneger JF, Kurland LT. Incidence of epilepsy and unprovoked seizures in Rochester, Minnesota: 1935–1984. Epilepsia 1993;34:453–68. [4] Keranen T, Sillanpaa M, Riekkinen PJ. Distribution of seizure types in an epileptic population. Epilepsia 1988;29:1–7. [5] Senanayake N. Classification on epileptic seizures: a hospital-based study of 1,250 patients in a developing country. Epilepsia 1993;34:812–8. [6] Hansen L, Chang S. Health research data for the real world: the MarketScan databases, white paper, Truven health analytics. http://truvenhealth.com/portals/0/ assets/PH_11238_0612_TEMP_MarketScan_WP_FINAL.pdf; 2011. [accessed 25.10.17. nDatabases, Accessed on Aug 22, 2017]. [7] Helmers SL, Thurman DJ, Durgin TL, Pai AK, Faught E. Descriptive epidemiology of epilepsy in the U.S. population: a different approach. Epilepsia 2015;56:942–8. [8] Wilner AN, Sharma BK, Thompson A, Soucy A, Krueger A. Diagnoses, procedures, drug utilization, comorbidities, and cost of health care for people with epilepsy in 2012. Epilepsy Behav 2014;41:83–90. [9] Fisher RS, Cross J, French JA, Higurashi N, Hirsch E, Hirsch J, et al. Operational classification of seizure types by the International League Against Epilepsy: position paper of the ILAE Commission for Classification and Terminology. Epilepsia 2017;58: 522–30. [10] Epilepsy Foundation. #Share my seizure. Available at: http://www.epilepsy.com/ make-difference/public-awareness/sharemyseizure, Accessed date: 22 August 2017. [11] Kim H, Thurman DJ, Durgin T, Faught E, Helmers S. Estimating epilepsy incidence and prevalence in the US pediatric population using nationwide health insurance claims data. J Child Neurol 2016;31(6):743–9.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004
Contents lists available at ScienceDirect
Epilepsy & Behavior journal homepage: www.elsevier.com/locate/yebeh
Epilepsy by the Numbers — from the US Centers for Disease Control and Prevention
People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy, and generalized nonconvulsive epilepsy—US MarketScan data, 2010–2015☆ Sanjeeb Sapkota a,⁎, Rosemarie Kobau b, Daniel M. Pastula b,c, Matthew M. Zack b a G2S Corporation, Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (CDC), Mail Stop F-78, 4770 Buford Hwy, 30341 GA, United States b Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, CDC, Mail Stop F-78, 4770 Buford Hwy, 30341 GA, United States c University of Colorado, School of Medicine and Colorado School of Public Health, Aurora, Colorado, United States
a r t i c l e
i n f o
Article history: Received 30 October 2017 Accepted 1 November 2017 Available online xxxx
a b s t r a c t The distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria. No recent US study has examined the distribution of epilepsy types in a large, population-based sample of people with epilepsy. We used MarketScan data from January 1, 2010 through September 30, 2015, to estimate the proportion of epilepsy types among all (N = 370,570) individuals diagnosed with epilepsy. We identified cases of epilepsy as individuals with at least one International Classification of Disease, 9th version (ICD-9) diagnostic code of 345.X and the use of at least one antiseizure drug described in the 2015 MarketScan Redbook. Unspecified epilepsy was more common (36.8%) than focal-localized epilepsy (24.6%), generalized convulsive epilepsy (23.8%), generalized nonconvulsive epilepsy (8.9%), other forms of epilepsy (5.2%), infantile spasm (0.3%), and epilepsia partialis continua (0.3%). The high proportion of epilepsy classified as unspecified might be lowered by improved training in epilepsy diagnosis and coding. © 2017 Elsevier Inc. All rights reserved.
1. Introduction People tend to think primarily of generalized convulsive seizures when considering epilepsy [1], but many are unaware of the different types of nonmotor and focal-onset seizures that have more nuanced signs and symptoms. This lack of awareness has multiple implications for public awareness efforts for education, symptom awareness, seizure first-aid, and stigma reduction. The reported distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria (e.g., classification guidelines; incident vs. prevalent cases; dominant seizure vs. all seizure types assessed) [2]. Among incident cases of epilepsy in Rochester, Minnesota (1935–1984), only 23% had generalized tonic–clonic seizures; about 57% had focal (formerly known as partial) seizures, and the rest had other generalized or unknown types [3]. This classic Rochester study, based on data from ☆ Disclaimer: The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. ⁎ Corresponding author at: G2S Corporation, Mail Stop F-78, Epilepsy Program, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (CDC), 4770 Buford Hwy, 30341 GA, United States. E-mail address: [email protected] (S. Sapkota).
1935 to 1984, often serves as a key reference for the distribution of seizure types among the US population [3]. Some international studies of clinical samples support a similar distribution of seizure types among classifiable epilepsies, with focal seizures being somewhat more common than generalized seizures [4,5]. But, in their review, Banerjee and colleagues [2] found nearly equal distributions of focal and generalized seizure types among clinical and population-based studies. These discrepancies depend on sample characteristics, different classification guidelines used by investigators, diagnostic limitations, case ascertainment criteria, and other methodological factors [2,4]. Our study uses a sample of US administrative claims data to examine the proportions of epilepsy types, to understand likely corresponding seizure types [3] among people with epilepsy of all ages. To our knowledge, no recent US study has examined the distribution of epilepsy types among a large, population-based sample of people with epilepsy. 2. Methods We used the Truven Health Analytics, Inc. MarketScan Commercial Claims and Encounters and Medicare Supplemental Database from across the United States, and the MarketScan Medicaid Multi-State Database representing 13 states [6]. In addition, we used MarketScan's
https://doi.org/10.1016/j.yebeh.2017.11.004 1525-5050/© 2017 Elsevier Inc. All rights reserved.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004
2
S. Sapkota et al. / Epilepsy & Behavior xxx (2017) xxx–xxx
statistical software, Treatment Pathways, to analyze the data set from January 1, 2010 through September 30, 2015. We defined cases of epilepsy as individuals with a claim that included at least one International Classification of Disease, 9th Revision (ICD-9) specific diagnostic code of 345.X and the use of at least one antiseizure drug from the 2015 MarketScan Redbook. We used the following codes: 345.0 (generalized nonconvulsive epilepsy); 345.1 (generalized convulsive epilepsy); 345.4 (localization-related [focal] [partial] epilepsy and epileptic syndromes with complex partial seizures); and 345.5 (localization-related [focal] [partial] epilepsy and epileptic syndromes with simple partial seizures); 345.6 (infantile spasms); 345.7 (epilepsia partialis continua, or recurrent focal motor seizures); 345.8 (other forms of epilepsy and recurrent seizures, such as anoxic epileptic seizure, benign occipital epilepsy of childhood—early onset variant, or benign Rolandic epilepsy); and 345.9 (epilepsy, unspecified). Because antiseizure drugs are typically prescribed for epilepsy and not for transient provoked seizures, requiring at least one prescription in our case definition adds to the specificity of the epilepsy diagnosis. We stratified seizure type among epilepsy cases by all ages and by children aged 0–17 years. We excluded two types of seizures classified with ICD-9 codes, 780.33 (posttraumatic seizure) and 780.39 (other seizure), because not all seizures in these categories are true epilepsy. We also excluded another two types of status epilepticus classified with ICD-9 codes, 345.3 (grand mal status) and 345.2 (petit mal status), because either code may be associated with various types of epilepsy, and because neither of them specifies a particular epilepsy type. Our epilepsy classification resembles that of Helmers and colleagues [7], except for excluding the above mentioned four types of epilepsy (i.e., 780.33, 780.39, 345.2, and 345.3). 3. Results The 2010–2015 MarketScan data included 78,489,988 individuals, of whom 370,570 (0.47%) were classified as having epilepsy, according to our case definition. These latter individuals represent prevalent cases of epilepsy between January 1, 2010 and September 30, 2015. Thirty percent of cases had two or more different epilepsy types assigned at different times. The most frequently occurring epilepsy type was unspecified epilepsy (ICD-9 code, 345.9 [n = 136,350 cases; 36.8%]) (Fig. 1), followed by localization-related focal epilepsy (ICD-9 codes
345.4 and 345.5 [n = 91,084 cases; 24.6%]); generalized convulsive epilepsy (ICD-9 code, 345.1 [n = 88,475 cases; 23.8%]); generalized nonconvulsive epilepsy (ICD-9 code, 345.0 [8.9%]); other forms of epilepsy (ICD-9 code, 345.8 [5.2%]); infantile spasms (ICD-9 code, 345.6 [0.3%]), and epilepsia partialis continua (ICD-9 code, 345.7 [0.3%]). Children with epilepsy showed the similar pattern of epilepsy types (Supplement).
4. Discussion Among all epilepsy types assessed in a large US sample of persons with epilepsy from the MarketScan data, unspecified epilepsy was the most common. Localized or focal epilepsy was the next most common epilepsy type, found among approximately one in four persons with epilepsy, as previously reported [3]. The percentage of cases with generalized convulsive epilepsy was smaller than focal or localized epilepsy. Of all cases of epilepsy, about 30% had a different epilepsy type assigned at different times. It is common for people with epilepsy to have more than one type of seizure and, therefore, be classified with more than one epilepsy type. It is also possible that both the preliminary diagnosis and the confirmed diagnosis for a case are retained in the data, or different physicians assigned the same patient different epilepsy types. In their examination of procedure codes by epilepsy diagnoses, Wilner and colleagues [8] found up to 16% of cases with unspecified epilepsy. The higher proportion in our study might be caused by medical chart coding limitations, insufficient diagnostic capacity among providers, early diagnoses before the diagnostic work-up was complete, or other factors. This suggests a need for improved provider education and coder training in epilepsy classification. Widespread dissemination of the new 2017 International League against Epilepsy guidelines on seizure classification among general and specialty providers and training for medical abstractors might facilitate appropriate epilepsy diagnosis and improved epilepsy classification [9]. The Centers for Disease Control and Prevention (CDC)-supported 2016 Epilepsy Foundation campaign, #ShareMySeizure, is designed to raise the US public's awareness of focal seizures, minimize stigma, and educate the public about appropriate seizure first-aid [10]. Although evaluation of this campaign is forthcoming, given how common focal
40 35 30
Percentages
25 20 15 10 5 0 Unspecified (ICD 9 Focal-Localized Generalized Generalized non- Other Form (ICD 9 Infanle Spasm Epilespia Paralis Code 345.9) (ICD 9 Codes Convulsive (ICD 9 convulsive (ICD 9 Code 345.8) (ICD 9 Code 345.6) Connua (ICD 9 345.4 and 345.5) Code 345.1) Code 345.0) Code 345.7) Types of Epilepsy
Fig. 1. Percentages of epilepsy types among people with epilepsy, MarketScan Data, United States, 2010–2015.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004
S. Sapkota et al. / Epilepsy & Behavior xxx (2017) xxx–xxx
seizures are, additional efforts to increase awareness of focal seizure symptoms may be warranted. This study has several limitations. First, the use of administrative claims data excludes 9% of US individuals without healthcare insurance, who may have a different distribution of epilepsy types. Second, since the quality of epilepsy diagnosis and classification in these data is unknown, some misclassification is likely. Third, the different durations of follow-up for cases in this study implies that some cases were more likely than other cases to have had a single, confirmed diagnosis over the course of a diagnostic workup. Fourth, 30% of the patients had multiple epilepsy types coded during the study period; this inflated our denominator of total epilepsy cases. However, our aim was not to limit cases to those with only one epilepsy type. Finally, the lower prevalence of epilepsy in our study (0.47%) than those in other studies based on MarketScan data, such as Kim and colleagues (0.68% in pediatric population) [11] and Helmers and colleagues (0.85% for all ages) [7], comes partly from our exclusion of 780.3x series of ICD-9 codes for epilepsy cases. Both ICD-9 codes, 780.33 (posttraumatic seizure) and 780.39 (other convulsions), are nonspecific and include a high proportion of provoked seizures. If they were not excluded, then the prevalence would be 0.5% among the pediatric population and 0.7% among the adult population. Findings from our study highlight the need to improve provider education and coder training for classifying epilepsy types. Researchers should continue to examine and refine claims data to enhance their knowledge about the effects of epilepsy, as well as to evaluate programs and care. Supplementary data to this article can be found online at https://doi. org/10.1016/j.yebeh.2017.11.004.
3
Conflict of interest The authors have no conflict of interest to report.
References [1] McNeil K, Brna PM, Gordon KE. Epilepsy in the twitter era: a need to re-tweet the way we think about seizures. Epilepsy Behav 2012;23:127–30. [2] Banerjee PN, Filippi D, Hauser WA. The descriptive epidemiology of epilepsy—a review. Epilepsy Res 2009;85:31–45. [3] Hauser WA, Anneger JF, Kurland LT. Incidence of epilepsy and unprovoked seizures in Rochester, Minnesota: 1935–1984. Epilepsia 1993;34:453–68. [4] Keranen T, Sillanpaa M, Riekkinen PJ. Distribution of seizure types in an epileptic population. Epilepsia 1988;29:1–7. [5] Senanayake N. Classification on epileptic seizures: a hospital-based study of 1,250 patients in a developing country. Epilepsia 1993;34:812–8. [6] Hansen L, Chang S. Health research data for the real world: the MarketScan databases, white paper, Truven health analytics. http://truvenhealth.com/portals/0/ assets/PH_11238_0612_TEMP_MarketScan_WP_FINAL.pdf; 2011. [accessed 25.10.17. nDatabases, Accessed on Aug 22, 2017]. [7] Helmers SL, Thurman DJ, Durgin TL, Pai AK, Faught E. Descriptive epidemiology of epilepsy in the U.S. population: a different approach. Epilepsia 2015;56:942–8. [8] Wilner AN, Sharma BK, Thompson A, Soucy A, Krueger A. Diagnoses, procedures, drug utilization, comorbidities, and cost of health care for people with epilepsy in 2012. Epilepsy Behav 2014;41:83–90. [9] Fisher RS, Cross J, French JA, Higurashi N, Hirsch E, Hirsch J, et al. Operational classification of seizure types by the International League Against Epilepsy: position paper of the ILAE Commission for Classification and Terminology. Epilepsia 2017;58: 522–30. [10] Epilepsy Foundation. #Share my seizure. Available at: http://www.epilepsy.com/ make-difference/public-awareness/sharemyseizure, Accessed date: 22 August 2017. [11] Kim H, Thurman DJ, Durgin T, Faught E, Helmers S. Estimating epilepsy incidence and prevalence in the US pediatric population using nationwide health insurance claims data. J Child Neurol 2016;31(6):743–9.
Please cite this article as: Sapkota S, et al, People with epilepsy are diagnosed most often with unspecified epilepsy, followed by focal epilepsy, generalized convulsive epilepsy..., Epilepsy Behav (2017), https://doi.org/10.1016/j.yebeh.2017.11.004