cause of death; death certificates; International Classification of Diseases; poisoning; SuperMICAR

Transcription

1 American Journal of Epidemiology The Author 1. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please Vol. 179, No. 7 DOI: 1.193/aje/kwt333 Advance Access publication: February 11, 1 Practice of Epidemiology Using Textual Cause-of-Death Data to Study Drug Poisoning Deaths Eric M. Ossiander* * Correspondence to Dr. Eric M. Ossiander, Washington State Department of Health, P.O. Box 71, Olympia, WA 9-71 ( eric.ossiander@doh.wa.gov). Initially submitted August 9, 13; accepted for publication December, 13. Death certificate data are often used to study the epidemiology of poisoning deaths, but the International Classification of Diseases (ICD) codes used to tabulate death data do not convey all of the available information about the drugs and other substances named on death certificates. In the United States and some other countries, the SuperMICAR computer system is used to assign ICD codes to deaths. The SuperMICAR system also stores a verbatim record of the text entered for the cause of death. We used the SuperMICAR text entries to study the 7,17 poisoning deaths that occurred among Washington State residents between 3 and 1. We tabulated the drugs named on death certificates and computed age-adjusted and age-specific death rates for the top-named drugs and for prescription and illicit drugs. Methadone was named on,19 death certificates and was the most frequently named substance, followed by alcohol, opiate, cocaine, oxycodone, and methamphetamine. For both men and women and at all ages, prescription drugs were involved in more deaths than were illicit drugs. Among the drugs named most frequently, only have unique ICD codes; the other 1 can be identified only by using the SuperMICAR data. cause of death; death certificates; International Classification of Diseases; poisoning; SuperMICAR Abbreviations: ICD, International Classification of Diseases; ICD-1, International Classification of Diseases, Tenth Revision. Poisoning deaths have increased in recent years, and poisoning has become the leading cause of injury death in the United States (1). In 1, there were almost 3, poisoning deaths in the United States, more than double the, deaths that occurred in (1). The primary source of information on these deaths is the death certificate data collected by the states and maintained by the National Center for Health Statistics (). Deaths are tabulated according to codes contained in the International Classification of Diseases (ICD), which is published by the World Health Organization and revised periodically. The Tenth Revision of the ICD (ICD-1) has been used since 1999 (3). The ICD-1 provides a detailed set of codes for classifying poisoning deaths, but it is not detailed enough to record all of the information that is recorded on death certificates. For example, among opioids, heroin and methadone have unique injury codes in the ICD-1 (T.1 and T.3, respectively), but oxycodone, hydrocodone, morphine, opiates, not otherwise specified, and many other opiates are all lumped together under the same code (T.). Fentanyl and tramadol are lumped in with other synthetic narcotics; and all barbiturates have the same code, as do all of the benzodiazepines. ICD codes may also provide an incomplete picture of the number of substances found in the body. If or more drugs with the same code are written on the same line of the death certificate, they will be represented by a single code. Beginning around the year, the SuperMICAR computer system was implemented in the United States to help classify causes of death () (Washington State, from which we drew data for this study, began using it in 3). With the SuperMICAR system, vital statistics staff key in the actual text written by the certifier on the cause-of-death portion of the death certificate. SuperMICAR parses the text and produces ICD codes for both multiple and underlying causes of death. The SuperMICAR output includes both the ICD codes and the text that was keyed into the program. Although the National Center for Health Statistics does not routinely release SuperMICAR files, they can be obtained from some state health departments. Our purpose in the present study was to demonstrate how SuperMICAR data can be used to analyze poisoning deaths Am J Epidemiol. 1;179(7): 9 on 13 May 1

2 Using SuperMICAR to Study Drug Poisoning Deaths and to present an analysis of deaths occurring in Washington State during 3 1. Although our main goal was to study drug poisoning deaths, we included deaths involving poisoning by other substances so we could ascertain the overlap between them. METHODS We used death data from the Washington State Department of Health for deaths of Washington residents occurring during 3 1. From these deaths, we extracted the 7,9 deaths for which the underlying-cause-of-death code indicated that the death was caused by poisoning. We included deaths resulting from all intents (unintentional, homicide, suicide, and undetermined) and included deaths due to poisoning by drugs and by other substances. We excluded deaths caused by complications of medical care. Our analysis included deaths coded as having an underlying cause of death in the ICD poisoning classifications (ICD-1 codes X X9, X X9, X X9, and Y1 Y19); it did not include deaths that were classified as being due to drug or alcohol dependence or the poisoning deaths that were due to adverse effects of drugs in therapeutic use. The cause-of-death section of the US standard death certificate () has lines in part I where the certifier is to enter the immediate cause of death and the conditions that led to that cause, with the underlying cause of death entered on the lowest line of part I. Part II of the cause-of-death section has 1 line where the certifier may enter other significant conditions contributing to death. For deaths due to an external cause, including poisoning deaths, the certifier is also required to fill in a box describing how the injury leading to the death occurred. A death certificate example for a person who died of drug poisoning in Washington State is shown in Figure 1. With the SuperMICAR system, vital statistics staff key into a computer the actual text that is written by the certifier on the death certificate (). Staff do not make any decisions regarding coding at the data entry stage. After data entry, the computer program interprets the textual entries and generates ICD codes describing both the multiple causes of death and the underlying cause of death, according to World Health Organization coding guidelines (). The textual entries are stored as string variables, with strings for each line in part I, one for the cause-of-death entry and one for the duration; a single string for part II; and a single string for the injury description. We prepared a subset of the Washington death data which contained records for all persons who died of poisoning, according to the underlying cause of death on the record. For each record, we combined the string variables holding the cause-of-death information and the injury description into a single string variable. Then we parsed this string into separate words. Word combinations that belong together, such as carbon monoxide or muscle relaxant, were treated as a Figure 1. Example of a death certificate for a person who died of drug poisoning in Washington State. For this illustration, the fields included in the SuperMICAR data (items 3,, and 3) are filled in; other fields are left blank. Am J Epidemiol. 1;179(7): 9 on 13 May 1

3 Ossiander single word. We processed the words through a spelling correction module that we developed and then matched them against a drug word list, which included the names of drugs or other chemical substances that could cause poisoning, and against a nondrug word list consisting of all other words that we found on death certificates. If a word did not match an entry in either list, we manually adjudicated whether it should be added to the spelling correction module (i.e., the word was a misspelled or alternative version of a word on the drug or nondrug list), the drug word list, or the nondrug word list. (We did not use a priori lists; for the first year of data, we manually adjudicated all of the words. After processing of the last year of data, the drug word list had 37 unique words and the nondrug list had,33 unique words.) By the end of the process, all words were classified as drug words or not. We retained the drug words for further processing. In the initial classification, we made no distinction between brand names and names of generic ingredients, and the drug word list contained both if both were found in the data. During processing, we converted brand names to their generic equivalents, for easier tabulation. Deaths involving injuries (including poisonings) receive ICD codes from distinct sets: one set describing the nature of the injury (e.g., broken leg ) and one set describing the external cause of the injury (e.g., fell off roof ). For poisonings, the injury codes describe the drug or other substance involved in the poisoning. Some injury codes describe a single drug (e.g., T.3 is methadone), while some describe a class of drugs (e.g., T.3 includes barbiturates ). The externalcause codes describe the 1 drug that is considered the main cause of death, but usually in broader classes, and they also denote the intent category (unintentional, homicide, suicide, or undetermined). We assigned an ICD injury code to each drug word. We also categorized each drug word into one of several broad categories (Appendix Table 1). Statistical analysis We conducted a descriptive analysis. We computed age-specific death rates for men, women, and both sexes together for the top named drugs to describe the relationship between age and poisoning deaths. To describe the temporal pattern during 3 1, we computed age-adjusted rates by the direct method, standardized to the US population (7). We also computed age-specific and age-adjusted rates of poisoning death according to whether the death certificate named a prescription drug, an illicit drug, both, or neither. We compiled counts of the most frequently named substances among all poisoning deaths, as well as among deaths where a prescription drug was named and deaths where an illicit drug was named. We tabulated the frequency with which pairs of drugs were named together on the same death certificate. We compiled counts of the most commonly named substances for each 3-digit ICD-1 external-cause-of-death category, for each ICD-1 poisoning injury code, and for each category of intent (unintentional, suicide, and undetermined). We conducted all analyses in SAS 9. (SAS Institute, Inc., Cary, North Carolina) and R.1. (). The word lists and computer code we used for processing and analyzing the data are available on the author s GitHub website ( This research involved only nonliving subjects and was determined to be exempt from institutional review board review. RESULTS There were 7,9 poisoning deaths among Washington State residents during 3 1. These included, unintentional deaths, 1,1 suicides, 11 homicides, 9 deaths of undetermined intent, and deaths caused by complications of medical or surgical care. This analysis excluded the poisoning deaths related to medical care (ICD-1 codes Y Y9) and included the 7,17 other poisoning deaths. The population of Washington State was,1, in 3 and rose to,7, in 1 (9). Methadone was mentioned on more of these death certificates (,19; 7.%) than any other substance, followed by alcohol, opiate, cocaine, and oxycodone (Table 1). The Table 1. The Most Frequently Mentioned Substances Associated With Poisoning Deaths Among Washington State Residents During 3 1 (n = 7,17) Rank Substance No. of Deaths, Where Named a 1 Methadone,19 Alcohol 1, 3 Opiate 1, Cocaine 1,17 Oxycodone 1,7 Methamphetamine 1 7 Morphine Diphenhydramine 7 9 Hydrocodone 3 1 Heroin Citalopram 33 1 Diazepam 13 Alprazolam 1 1 Amitriptyline Acetaminophen 39 1 Carbon monoxide Hydromorphone 9 1 Fluoxetine 3 19 Trazodone 7 Cyclobenzaprine 1 Venlafaxine Quetiapine Fentanyl 19 Sertraline 19 Bupropion 19 a Many death certificates mentioned more than 1 substance, so the total number of mentions is greater than the number of deaths. Substances named more than once on a death certificate were counted only once for each death. Am J Epidemiol. 1;179(7): 9 on 13 May 1

4 Using SuperMICAR to Study Drug Poisoning Deaths 7 only illicit drugs named among the top substances were cocaine, methamphetamine, and heroin. Among pairs of substances that were co-mentioned on certificates, there were substances that were named in all of the 1 most frequently named pairs: methadone, alcohol, cocaine, and opiate (Table ). The word opiate was mentioned on 1, (1.9%) certificates, but more than half (n =7)ofthese certificates also named a specific opiate. Age-specific death rates for each of the most commonly named substances showed similar age patterns among men and women, but women had lower rates for each of the substances except oxycodone, where the rates were similar between men and women (Figure ). The highest death rates were seen among men and women aged 9 years, with the exception that among women, the highest death rates for oxycodone and alcohol were at ages 9 years. In Washington State, the rate of deaths in which methadone or cocaine was mentioned reached a peak in (Figure 3). Oxycodone deaths may have started to decline in Washington in 9, and the methamphetamine death rate has remained fairly constant. The temporal patterns were similar between men and women, although, as noted above, women had lower death rates for each substance except oxycodone. At least 1 prescription drug was named in, (7%) of the poisoning deaths; at least 1 illicit drug in,1 (%) deaths; and in an additional 19 (3%) deaths, a drug that could be either prescription or illicit (e.g., opiate ) was named. The death rates for deaths in which only prescription drugs were mentioned were 3 times higher than those for deaths in which only illicit drugs or both illicit and prescription drugs were mentioned (Figure ). Prescription drug death rates increased during the period 3 and then began to fall, but illicit drug death rates remained constant during the entire period, suggesting that prescription drugs were not replacing illicit drugs. Prescription drug death rates were as high among women as among men, but women had lower death rates for deaths where only illicit drugs, both illicit and prescription drugs, or neither were mentioned. The death rates for all categories peaked at ages 9 years, except that the death rate for prescription drugs was slightly higher among women aged 9 years (Figure ). Prescription drug decedents tended to be slightly older than illicit drug decedents. The median age for prescription drug deaths was years; for illicit drugs, 3 years; for both, 3 years; and for neither, years. We listed the most frequently named substances for each 3-digit drug poisoning cause-of-death category with at least deaths (Table 3). Deaths that were known to be caused by methadone or oxycodone were classified in the X category. It is notable that these drugs were more frequently mentioned among deaths coded as X, a code which is used when multiple drugs that would be coded into different categories are mentioned in part I of the death certificate. The top drugs named among suicides were acetaminophen and diphenhydramine (an antihistamine which is a common ingredient in over-the-counter sleep aids) (Table ). Both drugs were often paired with oxycodone and hydrocodone, and diphenhydramine was also often paired with methadone (Table ). The top substances listed among undetermined Table. Frequently Mentioned Drug Pairs Among Poisoning Deaths of Washington State Residents, 3 1 (n = 7,17) a No. of Deaths Substance b Total Methadone Alcohol Opiate Cocaine Oxycodone Methamphetamine Morphine Diphenhydramine Hydrocodone Heroin Citalopram Diazepam Alprazolam Hydromorphone Acetaminophen Codeine Amitriptyline Methadone, Alcohol 1, Opiate 1, Cocaine 1, Oxycodone 1, Methamphetamine Morphine Diphenhydramine Hydrocodone Heroin For each of the 1 most frequently mentioned drugs (including alcohol), the table shows the 1 other drugs most frequently mentioned along with it. Drugs named more than once on a death certificate were counted only once for each death. a b Am J Epidemiol. 1;179(7): 9 on 13 May 1

5 Ossiander A) B) C) Death Rate per 1, Population Death Rate per 1, Population Death Rate per 1, Population Age, years Age, years Age, years Figure. Age-specific rates of the deaths for which the top drugs were named (per 1, population) among poisoning deaths in Washington State residents during 3 1. A) Both sexes; B) men; C) women. Solid line, methadone; dashed line, alcohol; dotted line, cocaine; dotted-and-dashed line, oxycodone; long-dashed line, methamphetamine. A) B) C) Death Rate per 1, Population 3 Death Rate per 1, Population 3 Death Rate per 1, Population Year Year Year Figure 3. Age-adjusted rates of the deaths for which the top drugs were named (per 1, population), by year, among poisoning deaths in Washington State residents during 3 1. A) Both sexes; B) men; C) women. Solid line, methadone; dashed line, alcohol; dotted line, cocaine; dotted-and-dashed line, oxycodone; long-dashed line, methamphetamine. Am J Epidemiol. 1;179(7): 9 on 13 May 1

6 Using SuperMICAR to Study Drug Poisoning Deaths 9 A) B) C) Death Rate per 1, Population Death Rate per 1, Population Death Rate per 1, Population Year Year Year Figure. Age-adjusted rates of poisoning death (per 1, population) according to the category of drugs named on the death certificate, by sex and year, among poisoning deaths in Washington State residents during 3 1. A) Both sexes; B) men; C) women. Solid line, prescription drugs; dashed line, illicit drugs; dotted line, both prescription and illicit drugs; dotted-and-dashed line, neither prescription nor illicit drugs. A) B) C) Death Rate per 1, Population 1 Death Rate per 1, Population 1 Death Rate per 1, Population Age, years Age, years Age, years Figure. Age-specific rates of poisoning death (per 1, population) according to the category of drugs named on the death certificate, by sex and age group, among poisoning deaths in Washington State residents during 3 1. A) Both sexes; B) men; C) women. Solid line, prescription drugs; dashed line, illicit drugs; dotted line, both prescription and illicit drugs; dotted-and-dashed line, neither prescription nor illicit drugs. Am J Epidemiol. 1;179(7): 9 on 13 May 1

7 9 Ossiander Table 3. Most Commonly Listed Substances Associated With Specific ICD-1 Causes of Death (For Codes With At Least Deaths) Among Poisoning Deaths in Washington State Residents During 3 1 (n = 7,17) ICD-1 Code X X1 X ICD-1 Cause of Death Description Unintentional; nonopioid analgesics, antipyretics, and antirheumatics Unintentional; antiepileptic, sedative-hypnotic, antiparkinsonism and psychotropic drugs, NEC Unintentional; narcotics and psychodysleptics (hallucinogens), NEC Total No. of Deaths Top Named Substances (No. of Deaths) a 3 Acetaminophen (7), tramadol (), alcohol (), salicylate (), aspirin (1) 7 Methamphetamine (79), alcohol (7), citalopram (3), amitriptyline (9), fluoxetine (1),3 Methadone (9), cocaine (1), alcohol (9), heroin (37), oxycodone (1) X Unintentional; other and unspecified drugs,7 Methadone (1,), oxycodone (), alcohol (), cocaine (9), diazepam (379) X Unintentional; alcohol 1 Alcohol (1), opiate (3), amitriptyline (), isopropanol (), methanol () X7 Unintentional; other gases and vapors 13 Carbon monoxide (9), fumes (17), propane (1), smoke inhalation (1), vehicle exhaust (13) X X1 X Intentional self-harm; nonopioid analgesics, antipyretics, and antirheumatics Intentional self-harm; antiepileptic, sedative-hypnotic, antiparkinsonism and psychotropic drugs, NEC Intentional self-harm; narcotics and psychodysleptics (hallucinogens), NEC Acetaminophen (3), salicylate (1), aspirin (), alcohol (), diphenhydramine () 3 Amitriptyline (), alcohol (), quetiapine (37), bupropion (), citalopram () 11 Methadone (9), oxycodone (), alcohol (1), morphine (), opiate (1) X Intentional self-harm; other and unspecified drugs Diphenhydramine (11), acetaminophen (13), alcohol (11), oxycodone (1), hydrocodone (3) X Intentional self-harm; organic solvents and halogenated hydrocarbons and their vapors Ethylene glycol (), antifreeze (), benzene (1), chloroform (1) X7 Intentional self-harm; other gases and vapors 33 Carbon monoxide (79), vehicle exhaust (133), fumes (), engine exhaust (), alcohol (9) Y11 Y1 Undetermined intent; antiepileptic, sedative-hypnotic, antiparkinsonism and psychotropic drugs, NEC Undetermined intent; narcotics and psychodysleptics (hallucinogens), NEC 9 Methamphetamine (1), alcohol (), olanzapine (), quetiapine (), bupropion () 1 Methadone (), cocaine (9), heroin (), alcohol (1), morphine (1) Y1 Undetermined intent; other and unspecified drugs Methadone (71), diphenhydramine (39), alcohol (3), methamphetamine (31), oxycodone (31) Abbreviations: ICD-1, International Classification of Diseases, Tenth Revision; NEC, not elsewhere classified. a The word opiate was counted only when a specific opiate was not named on the death record. deaths showed commonalities with both the unintentional list and the suicide list. The top substances on the undetermined list were the same as the top substances on the unintentional list, with methadone being the most frequently named substance on both lists. However, the undetermined list also included diphenhydramine and acetaminophen, which were not on the unintentional list. The ICD-1 multiple-cause-of-death codes include both the underlying causes of deaths (shown in Table 3)and the injury codes for all of the individual substances named on the death certificate. In the ICD-1, injury codes for poisoning range from T3. to T.9. We listed the most commonly named substances for each injury code that was associated with at least 1 deaths (Table ). The list illustrates the additional specificity that may be obtained with the SuperMICAR data, as compared with the ICD-1 injury codes. Some injury codes are synonymous with a single drug: T.1 is heroin, T.3 is methadone, and T. is cocaine. However, other injury codes include many different drugs: T. includes oxycodone, hydrocodone, hydromorphone, and other drugs; and T3. includes citalopram, fluoxetine, and other drugs. DISCUSSION The SuperMICAR data system contains all of the text entered by the certifier on the cause-of-death portion of the death certificate. We parsed this text to list the individual words and phrases describing the cause of death and separated the words naming poisoning-related substances or diseases from all other words. We found that these words provided much more detail than the ICD codes. Among the most frequently mentioned poisoning-related substances on Washington State death certificates during 3 1, onlyhaveanicdcodethatspecifically identifies them: methadone, alcohol, cocaine, and heroin. The other 1 have ICD codes that include multiple substances and therefore cannot be definitively identified or counted in data files that include only the ICD codes. We were also able to classify drugs as prescription, illicit, or other and to count the numbers of deaths associated with prescription drugs, illicit drugs, both, or neither. Our data suggest that prescription drugs are associated with many more poisoning deaths in Washington State than Am J Epidemiol. 1;179(7): 9 on 13 May 1

8 Using SuperMICAR to Study Drug Poisoning Deaths 91 Table. The 1 Most Commonly Listed Substances for Each Intent Category Associated With Poisoning Deaths Among Washington State Residents During 3 1 (n = 7,17) Intent Total No. of Deaths Most Commonly Named Substances (No. of Deaths) a Unintentional, Methadone (1,91), alcohol (1,11), cocaine (1,), oxycodone (7), methamphetamine (), morphine (), heroin (9), opiate (7), hydrocodone (37), citalopram () Suicide 1,1 Carbon monoxide (), alcohol (19), acetaminophen (17), diphenhydramine (1), vehicle exhaust (137), oxycodone (1), amitriptyline (111), hydrocodone (9), citalopram (), methadone (3) Undetermined 9 Methadone (11), alcohol (9), cocaine (3), oxycodone (), morphine (7), methamphetamine (), diphenhydramine (39), acetaminophen (3), heroin (3), opiate (3) a The word opiate was counted only when a specific opiate was not named on the death record. are other drugs. Prescription drugs were named on more than twice as many death certificates as were illicit drugs. For both men and women, the rate of deaths in which only prescription drugs were named was higher throughout 3 1 than therateofdeathsinwhichillicit drugs, both prescription and illicit drugs, or neither were named. Methadone was the most often named prescription drug on death certificates, followed by oxycodone, morphine, diphenhydramine, and hydrocodone. The presence of diphenhydramine among the most often named prescription drugs was a surprise. Diphenhydramine is an antihistamine that is an ingredient in many over-thecounter anti-allergy drugs and sleep aids. It is also an anticholinergic (1) and euphoriant which potentiates the effects of opiates and some other drugs (11). Its ICD-1 injury code is T., a code it shares with dozens of other drugs (1), and therefore its role in deaths could not have been ascertained with the ICD codes alone. In contrast to diphenhydramine, oxycodone is well-known as a contributor to drug poisoning deaths (13, 1). In the ICD-1, oxycodone is coded as T., the code for other opioids, a code it shares with all opioids other than opium, methadone, and heroin, each of which has a unique code. Therefore, the occurrence of oxycodone deaths cannot be tabulated from ICD codes alone, and it has usually been studied with coroner or medical examiner reports (13, 1, 1). In the United States, most coroner and medical examiner data are maintained in counties, of which there are more than 3,. Obtaining these records and then manually reviewing them to tabulate oxycodone deaths requires far more resources than using the SuperMICAR data. The SuperMICAR data also provide a more complete picture of the number of different drugs named on the death certificate than ICD codes do. A convention in coding cause of death is to not use the same code more than once on each line of the death certificate. So, for example, if a certifier wrote on line 1 fentanyl and tramadol, both of which have the ICD-1 code T., the multiple-cause-of-death codes would include only a single code of T. on that line. However, if the certifier named the same drug on different lines of the death certificate, then that drug would be coded twice, and an analyst using the ICD codes would not know whether the codes represented different drugs that had the same code or the same drug named twice. The SuperMICAR text data have been used in a handful of other studies. In Australia, Butt et al. (17) used it, along with the multiple-cause-of-death ICD codes, to develop a machinelearning classifier to identify deaths for which there was a notifiable cancer on the death certificate. Davis et al. (1) fed SuperMICAR data through a natural language processor to develop a system for identifying pneumonia and influenza deaths. A national surveillance system for Creutzfeldt-Jakob disease in the United States has used SuperMICAR text data since 1999 (19) (although SuperMICAR data were not available from all states until 3). Use of the literal text from death certificates has allowed the surveillance system to identify and count cases of Creutzfeldt-Jakob disease consistently even though an ICD coding change led to inconsistencies in the counts derived from ICD codes. Some of the main findings we describe in the present study have also been described elsewhere. There are unique ICD-1 codes for methadone, heroin, and cocaine, and these have been used to describe trends in deaths from some of those drugs ( ). Some studies have also used ICD-1 codes to describe the increase in prescription opioid overdose deaths and have presented results similar to ours (3, ), even though the ICD-1 codes they used for prescription opioids (T. T.) may have also included some deaths from nonprescription opioids. The SuperMICAR system was developed by the National Center for Health Statistics in the United States, but it is also used in several other countries, including Canada (), Australia (17), and South Africa (). Systems that combine the National Center for Health Statistics SuperMICAR program with local enhancements are used in England, Brazil, Japan, and several other countries (). Several features of SuperMICAR data make them more difficult to use than ICD codes. Since the information is free-text, computer processing is needed before the data can be tabulated. Parsing the text into words can be accomplished automatically with many different computer systems, including SAS, which we used. However, the individual words may lose their meaning without the context in which they were used. For example, the individual words in calcium channel blocker or car exhaust don t have the same meaning as the terms themselves. Therefore, it is necessary to build a computer routine to identify and construct phrases. It is also necessary to have a routine to correct misspellings, as these are frequent in the SuperMICAR data. In our data, we found a total of 37 words describing drugs orother substancesthat could causepoisoning. Combined, these words were misspelled in different ways, with some words, such as cyclobenzaprine and quetiapine, being misspelled in more than 1 different ways. We constructed a spelling Am J Epidemiol. 1;179(7): 9 on 13 May 1

9 9 Ossiander Table. Most Commonly Listed Substances Associated With Specific ICD-1 Poisoning Injury Codes (For Codes With At Least 1 Deaths) Among Poisoning Deaths in Washington State Residents During 3 1 (n = 7,17) ICD-1 Code ICD-1 Injury Code Description Total No. of Deaths Most Commonly Named Substance(s) (No. of Deaths) a T39.1 -Aminophenol derivatives 39 Acetaminophen (39) T.1 Heroin 39 Heroin (39) T. Other opioids,7 Oxycodone (1,7), morphine (), hydrocodone (3), opiate (3), hydromorphone (9), codeine (1) T.3 Methadone,19 Methadone (,19) T. Other synthetic narcotics 1 Fentanyl (19), tramadol (13), propoxyphene (11) T. Cocaine 1,17 Cocaine (1,17) T.3 Barbiturates 1 Butalbital (7), phenobarbital (3) T. Benzodiazepines 1,311 Diazepam (), alprazolam (1), benzodiazepine (13), clonazepam (1), temazepam (11), lorazepam (19) T. Other antiepileptic and sedative-hypnotic 3 Gabapentin (1), zolpidem (1), topiramate (), lamotrigine () drugs T. Antiparkinsonism drugs and other central 1 Carisoprodol (139), methocarbamol (3) muscle-tone depressants T3. Tricyclic and tetracyclic antidepressants 79 Amitriptyline (397), doxepin (13), nortriptyline (13), mirtazapine (13) T3. Other and unspecified antidepressants 1,1 Citalopram (33), fluoxetine (3), trazodone (7), venlafaxine (), sertraline (19), bupropion (19), paroxetine (137) T3.3 Phenothiazine antipsychotics and neuroleptics 1 Promethazine (113) T3. Butyrophenone and thioxanthene neuroleptics Quetiapine (199), meprobamate (1), hydroxyzine (79), olanzapine (73) T3. Psychostimulants with abuse potential 7 Methamphetamine (1), amphetamine (3) T. Antiallergic and antiemetic drugs Diphenhydramine (7), doxylamine (9) T.1 Skeletal muscle relaxants Cyclobenzaprine () T.3 Antitussives 139 Dextromethorphan (139) T1. Ethanol 1, Alcohol (1,) T Carbon monoxide 1 Carbon monoxide (39), vehicle exhaust (1) T9.9 Gases, fumes, and vapors, unspecified 11 Fumes (1) Abbreviation: ICD-1, International Classification of Diseases, Tenth Revision. a The word opiate was counted only when a specific opiate was not named on the death record. correction list by examining all words that did not match our list of drug words. It may be possible in some cases to use a publicly available spell-checker, as Davis et al. did (1), but we did not explore that option. There are other limitations to SuperMICAR data. We counted the number of times heroin and morphine were named on death certificates and reported those numbers without qualification. Morphine is a metabolite of heroin, and when laboratory tests find morphine in samples taken from a decedent, it is not always possible to tell which drug the decedent took (7). The cause-of-death certifier may also use death scene evidence to determine which drug was used, but the way in which certifiers do that may not be consistent across counties or states. States vary in the completeness with which drugs are specified on death certificates (). Specific drugs were named on 93% of drug poisoning death certificates in Washington State during 1, well above the national figure of 7%; in some states, specific drugs were named on fewer than % of certificates (). SuperMICAR data would be less useful for studying drug deaths in those states than we have shown it to be in Washington State. Privacy considerations may lead some agencies to restrict access to SuperMICAR data, because it may sometimes contain text that discloses private information about the decedent or another person. The SuperMICAR text includes the death certificate entry that describes how the injury leading to the death occurred, and this entry occasionally includes a street address, the name of the decedent, or the name of another person who was involved in the death or who found the injured decedent. In conclusion, we found that SuperMICAR data provided details about drug poisoning deaths that could not be obtained from the ICD cause-of-death codes alone. The information from SuperMICAR allowed us to tabulate the actual drugs named on drug poisoning death certificates, to study the frequency of drug combinations, and to classify deaths as being Am J Epidemiol. 1;179(7): 9 on 13 May 1

10 Using SuperMICAR to Study Drug Poisoning Deaths 93 associated with prescription or illicit drugs. Many of the most frequently named drugs on death certificates are assigned ICD codes that contain many different drugs, and therefore they cannot be identified by the ICD code alone. In Washington State during 3 1, prescription drugs were associated with more poisoning deaths than were illicit drugs. This was true among both men and women and at all ages. Although women had lower rates of death associated with illicit drugs than men, their rates of death associated with prescription drugs were similar to those of men. Methadone was the most frequently named drug, followed by alcohol, cocaine, oxycodone, and methamphetamine. ACKNOWLEDGMENTS Author affiliation: Washington State Department of Health, Olympia, Washington (Eric M. Ossiander). This work was supported by the Washington State Department of Health and received no external funding. I thank Dr. Jennifer Sabel of the Washington State Department of Health for valuable comments. An early version of these findings was presented at the 7th Annual Meeting of the Society for Epidemiologic Research, Seattle, Washington, June 7, 1. Conflict of interest: none declared. REFERENCES 1. Centers for Disease Control and Prevention. Fatal Injury Reports , National or Regional [database]. ( (Accessed July 9, 13).. Freedman MA, Weed JA. The National Vital Statistics System. In: O Carroll PW, Yasnoff WA, Ward ME, et al., eds. Public Health Informatics and Information Systems. New York, NY: Springer-Verlag New York; 3:9. 3. World Health Organization. International Statistical Classification of Diseases and Related Health Problems. Tenth Revision.Vol.1. Geneva, Switzerland: World Health Organization; Glenn D. Description of the National Center for Health Statistics software systems and demonstrations. In: Peters KD, ed. 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11 9 Ossiander Appendix Table 1. General Categories Into Which All Drug-Related Words Were Classified Category Prescription Illicit Either OTC Alcohol Nonspecific Common Disease Unknown Description A drug that is normally obtained through a prescription or used in a clinic A drug that is normally obtained on the street and is usually illegal A term that may denote either a prescription drug or an illicit drug (e.g., opiate) A drug normally used to treat illness and that can be obtained legally without a prescription (e.g., aspirin) Any word denoting alcohol (but not alcoholism) Any word denoting a drug that does not name a drug (e.g., polypharmacy, drug, or tablet) Commonly available substances that either are not meant for ingestion (e.g., automobile exhaust, arsenic, butane) or are commonly consumed but are not illicit and not meant to treat an illness (e.g., caffeine, tobacco) A word denoting a medical condition or treatment (e.g., alcoholism, anticoagulation) A word with an unknown meaning (probably a misspelling) Abbreviation: OTC, over-the-counter. Am J Epidemiol. 1;179(7): 9 on 13 May 1