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Details in Operational Definitions of Length of Visit and Boarding Variables in the National Hospital Ambulatory Medical Care Survey
CORRESPONDENCE
Guidelines for Letters to the Editor Annals welcomes letters to the editor, including observations, opinions, corrections, very brief reports, and comments on published articles. Letters to the editor should not exceed 500 words and 5 references. They should be submitted using Annals’ Web-based peer review system, Editorial Manager™ (http://www. editorialmanager.com/annemergmed). Annals no longer accepts submissions by mail. Letters should not contain abbreviations. Financial association or other possible conflicts of interest should always be disclosed, and their presence or absence will be published with the correspondence. Letters discussing an Annals article must be received within 8 weeks of the article’s publication. Published letters may be edited and shortened. Authors of articles for which comments are received will be given the opportunity to reply. If those authors wish to respond, their reply will not be shared with the author of the letter before publication. Neither Annals of Emergency Medicine nor the Publisher accepts responsibility for statements made by contributors.
0196-0644/$-see front matter Copyright © 2013 by the American College of Emergency Physicians.
Details in Operational Definitions of Length of Visit and Boarding Variables in the National Hospital Ambulatory Medical Care Survey To the Editor: We read with great interest the insightful editorials addressing the National Hospital Ambulatory Medical Care Survey (NHAMCS) in the December 2012 edition of Annals, as well as the accompanying original research articles.1-3 As part of our recent exploration of the publicly available NAHMCS-ED (emergency department) data and data dictionaries, we noted ambiguity in the length of visit variable definition. In the 2008 publicly available data dictionary, the length of visit variable is defined as “LENGTH OF VISIT (minutes) Calculated from PRF Q1.d, date and time of ED arrival and Discharge.”4 We queried the Centers for Disease Control and Prevention (CDC) about the operational definition of ED “discharge” and whether this included boarding time and received the following response: “. . . [B]oarding applies to about 10% of the sample . . . . [F]or 75% of visits with boarding, [length of visit] includes the entire boarding time. For the remaining 917 visits, the BOARDED time does increase the [length of visit], but by how much depends on what time the bed was actually requested, and that variable is not on the public use file.” Further, they noted that “you should not add [length of visit] and BOARDED together, because the bed can be requested while the patient is still in the ED . . . . If you are interested in conducting an in-depth analysis on these variables, you may want to consider coming to the research data center and using the restricted files.” Thus, in the case of the publicly available NHAMCS-ED data, the time spent under the care of an ED provider is unclear. For hospitalized patients, discharge from the ED apparently indicates a time close to bed request, but in other 548 Annals of Emergency Medicine
cases it indicates the time the patient physically left the ED. However, this variability was not immediately apparent in the publicly available data dictionary, and it was not until we personally contacted the CDC that this was revealed. Analyses based partially or entirely on the length of visit variable may not accurately represent the true ED length of stay, independent of boarding time. For example, in the case of the wellwritten and intriguing article by Pitts et al,3 ambiguity in coding of the length of visit variable may have resulted in erroneous attribution of testing, procedures, and treatment to ED providers. Patients boarding in the ED who underwent additional testing or therapy after transition of care to the hospital-based team while remaining physically in the ED may have erroneously been counted among active ED patients. We believe that NHAMCS, given its wealth of important data, will continue to be a valuable database for emergency medicine research. However, we agree with the accompanying editorial by Cooper2 that investigators, reviewers, and readers must be more critical in evaluation of the data and what the variables truly represent. The complexities of ED boarding, observation unit admissions, and clearly defining when transfer of care occurs are topics of great interest to emergency medicine research but are also topics that are challenging to clearly delineate in these large federal databases. Candace D. McNaughton, MD, MPH James Parnell, MD Tyler W. Barrett, MD, MSCI Department of Emergency Medicine Vanderbilt University Medical Center Nashville, TN http://dx.doi.org/10.1016/j.annemergmed.2013.02.032
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Correspondence Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). CDN is supported by the National Institutes of Health K12 HL109019. TWB is supported by the National Institute of Health grant K23 HL102069. 1. McCaig LF, Burt CW. Understanding and interpreting the National Hospital Ambulatory Medical Care Survey: key questions and answers. Ann Emerg Med. 2012;60:716-721.e1. 2. Cooper RJ. NHAMCS: does it hold up to scrutiny? Ann Emerg Med. 2012;60:722-725. 3. Pitts SR, Pines JM, Handrigan MT, et al. National trends in emergency department occupancy, 2001 to 2008: effect of inpatient admissions versus emergency department practice intensity. Ann Emerg Med. 2012;60:679-686.e3. 4. Centers for Disease Control and Prevention. Ambulatory health care data. Available at: http://www.cdc.gov/nchs/ahcd/ahcd_ questionnaires.htm, doc08. Page 31. Accessed November 26, 2012.
In reply: We thank Drs. McNaughton, Parnell, and Barrett for a close reading of our article analyzing trends in emergency department (ED) volume and occupancy.1 One of their concerns is moot: our study interval did not include the years after 2008, when a separate “boarding” time was included in the National Hospital Ambulatory Medical Care Survey (NHAMCS) for patients who were hospitalized, defined as the duration from “time a decision was made to hospitalize” to actual ED departure. As a convenient proxy for this “decision time” in 2009, the survey subsequently chose the “time bed requested,” which seems reasonable, given the expectation of a huge variety of documentation styles nationally. We hope that the new Centers for Medicare & Medicaid Services throughput interval reporting requirement will define this decision time explicitly, thus incentivizing accuracy and reduced missingness for this key operational time stamp in future versions of the NHAMCS-ED survey. During the survey years included in our study (2001 to 2008), there was instead simply a report of “discharge time,” regardless of admission status. In the appendix, we commented on the possible role that semantic ambiguity might have played in the higher rates of missingness of length of visit in the earlier of these years, when this was a new item. Because throughput measures had not yet gained currency, we have no way to know whether an admitted patient was boarded in the ED after the discharge time, or whether the actual time of departure was recorded as the discharge time, thus including the boarding time in the overall length of visit. We assume that both cases occurred and therefore that our findings represent imprecise but relatively accurate estimates of what we intended. However, among persons discharged home, a precisely defined boarding interval is not relevant. Figure 4 in our article shows that hospital admission in fact had little influence on our main observation that throughput factors had a greater effect on Volume , . : November
the growth in crowding than boarding did. We do not believe that procedures meant to be conducted in the hospital were erroneously attributed to emergency physicians in our study. And we do believe that scarce inpatient beds and unreliable primary care have caused emergency physicians to practice a more intensive style of medicine. Stephen R. Pitts, MD, MPH Emory University School of Medicine Department of Emergency Medicine Atlanta, GA http://dx.doi.org/10.1016/j.annemergmed.2013.03.039
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The author has stated that no such relationships exist. 1. Pitts SR, Pines JM, Handrigan MT, et al. National trends in emergency department occupancy, 2001 to 2008: effect of inpatient admissions versus emergency department practice intensity. Ann Emerg Med. 2012;60:679-686.
NHAMCS: Does It Hold Up to Scrutiny? To the Editor: The Centers for Disease Control and Prevention’s (CDC’s) National Center for Health Statistics (NCHS) is committed to collecting and disseminating high-quality data that meet the information needs of a wide range of users. We take issue with the unfavorable assessment of National Hospital Ambulatory Medical Care Survey (NHAMCS) data in a recent editorial by Cooper1 and appreciate the opportunity to respond to her comments. We agree with Cooper1 that research findings need to be critically assessed, and we appreciate the guidelines she provides for potential authors using NHAMCS data, which are consistent with our recent article.2 We are troubled, however, by her sweeping indictment of the NHAMCS data-gathering process and her concern that medical practice or policy may have changed based on “the false assumption that the data were valid.”1 In fact, the authors cited by Cooper1 appropriately assessed the limitations of using NHAMCS data3-6 and reported that their findings3-5 were consistent with previous research. In cases in which findings from studies diverge, it is important to consider the methodology of each study. A particular strength of NHAMCS is that it includes hospitals other than academic medical centers, which commonly serve as the settings for research studies, thereby giving a more complete picture of health care use patterns. When comparing data from NHAMCS with other studies, one should always be careful to keep such methodological differences in mind before making conclusions about validity. Annals of Emergency Medicine 549
Guidelines for Letters to the Editor Annals welcomes letters to the editor, including observations, opinions, corrections, very brief reports, and comments on published articles. Letters to the editor should not exceed 500 words and 5 references. They should be submitted using Annals’ Web-based peer review system, Editorial Manager™ (http://www. editorialmanager.com/annemergmed). Annals no longer accepts submissions by mail. Letters should not contain abbreviations. Financial association or other possible conflicts of interest should always be disclosed, and their presence or absence will be published with the correspondence. Letters discussing an Annals article must be received within 8 weeks of the article’s publication. Published letters may be edited and shortened. Authors of articles for which comments are received will be given the opportunity to reply. If those authors wish to respond, their reply will not be shared with the author of the letter before publication. Neither Annals of Emergency Medicine nor the Publisher accepts responsibility for statements made by contributors.
0196-0644/$-see front matter Copyright © 2013 by the American College of Emergency Physicians.
Details in Operational Definitions of Length of Visit and Boarding Variables in the National Hospital Ambulatory Medical Care Survey To the Editor: We read with great interest the insightful editorials addressing the National Hospital Ambulatory Medical Care Survey (NHAMCS) in the December 2012 edition of Annals, as well as the accompanying original research articles.1-3 As part of our recent exploration of the publicly available NAHMCS-ED (emergency department) data and data dictionaries, we noted ambiguity in the length of visit variable definition. In the 2008 publicly available data dictionary, the length of visit variable is defined as “LENGTH OF VISIT (minutes) Calculated from PRF Q1.d, date and time of ED arrival and Discharge.”4 We queried the Centers for Disease Control and Prevention (CDC) about the operational definition of ED “discharge” and whether this included boarding time and received the following response: “. . . [B]oarding applies to about 10% of the sample . . . . [F]or 75% of visits with boarding, [length of visit] includes the entire boarding time. For the remaining 917 visits, the BOARDED time does increase the [length of visit], but by how much depends on what time the bed was actually requested, and that variable is not on the public use file.” Further, they noted that “you should not add [length of visit] and BOARDED together, because the bed can be requested while the patient is still in the ED . . . . If you are interested in conducting an in-depth analysis on these variables, you may want to consider coming to the research data center and using the restricted files.” Thus, in the case of the publicly available NHAMCS-ED data, the time spent under the care of an ED provider is unclear. For hospitalized patients, discharge from the ED apparently indicates a time close to bed request, but in other 548 Annals of Emergency Medicine
cases it indicates the time the patient physically left the ED. However, this variability was not immediately apparent in the publicly available data dictionary, and it was not until we personally contacted the CDC that this was revealed. Analyses based partially or entirely on the length of visit variable may not accurately represent the true ED length of stay, independent of boarding time. For example, in the case of the wellwritten and intriguing article by Pitts et al,3 ambiguity in coding of the length of visit variable may have resulted in erroneous attribution of testing, procedures, and treatment to ED providers. Patients boarding in the ED who underwent additional testing or therapy after transition of care to the hospital-based team while remaining physically in the ED may have erroneously been counted among active ED patients. We believe that NHAMCS, given its wealth of important data, will continue to be a valuable database for emergency medicine research. However, we agree with the accompanying editorial by Cooper2 that investigators, reviewers, and readers must be more critical in evaluation of the data and what the variables truly represent. The complexities of ED boarding, observation unit admissions, and clearly defining when transfer of care occurs are topics of great interest to emergency medicine research but are also topics that are challenging to clearly delineate in these large federal databases. Candace D. McNaughton, MD, MPH James Parnell, MD Tyler W. Barrett, MD, MSCI Department of Emergency Medicine Vanderbilt University Medical Center Nashville, TN http://dx.doi.org/10.1016/j.annemergmed.2013.02.032
Volume , . : November
Correspondence Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). CDN is supported by the National Institutes of Health K12 HL109019. TWB is supported by the National Institute of Health grant K23 HL102069. 1. McCaig LF, Burt CW. Understanding and interpreting the National Hospital Ambulatory Medical Care Survey: key questions and answers. Ann Emerg Med. 2012;60:716-721.e1. 2. Cooper RJ. NHAMCS: does it hold up to scrutiny? Ann Emerg Med. 2012;60:722-725. 3. Pitts SR, Pines JM, Handrigan MT, et al. National trends in emergency department occupancy, 2001 to 2008: effect of inpatient admissions versus emergency department practice intensity. Ann Emerg Med. 2012;60:679-686.e3. 4. Centers for Disease Control and Prevention. Ambulatory health care data. Available at: http://www.cdc.gov/nchs/ahcd/ahcd_ questionnaires.htm, doc08. Page 31. Accessed November 26, 2012.
In reply: We thank Drs. McNaughton, Parnell, and Barrett for a close reading of our article analyzing trends in emergency department (ED) volume and occupancy.1 One of their concerns is moot: our study interval did not include the years after 2008, when a separate “boarding” time was included in the National Hospital Ambulatory Medical Care Survey (NHAMCS) for patients who were hospitalized, defined as the duration from “time a decision was made to hospitalize” to actual ED departure. As a convenient proxy for this “decision time” in 2009, the survey subsequently chose the “time bed requested,” which seems reasonable, given the expectation of a huge variety of documentation styles nationally. We hope that the new Centers for Medicare & Medicaid Services throughput interval reporting requirement will define this decision time explicitly, thus incentivizing accuracy and reduced missingness for this key operational time stamp in future versions of the NHAMCS-ED survey. During the survey years included in our study (2001 to 2008), there was instead simply a report of “discharge time,” regardless of admission status. In the appendix, we commented on the possible role that semantic ambiguity might have played in the higher rates of missingness of length of visit in the earlier of these years, when this was a new item. Because throughput measures had not yet gained currency, we have no way to know whether an admitted patient was boarded in the ED after the discharge time, or whether the actual time of departure was recorded as the discharge time, thus including the boarding time in the overall length of visit. We assume that both cases occurred and therefore that our findings represent imprecise but relatively accurate estimates of what we intended. However, among persons discharged home, a precisely defined boarding interval is not relevant. Figure 4 in our article shows that hospital admission in fact had little influence on our main observation that throughput factors had a greater effect on Volume , . : November
the growth in crowding than boarding did. We do not believe that procedures meant to be conducted in the hospital were erroneously attributed to emergency physicians in our study. And we do believe that scarce inpatient beds and unreliable primary care have caused emergency physicians to practice a more intensive style of medicine. Stephen R. Pitts, MD, MPH Emory University School of Medicine Department of Emergency Medicine Atlanta, GA http://dx.doi.org/10.1016/j.annemergmed.2013.03.039
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The author has stated that no such relationships exist. 1. Pitts SR, Pines JM, Handrigan MT, et al. National trends in emergency department occupancy, 2001 to 2008: effect of inpatient admissions versus emergency department practice intensity. Ann Emerg Med. 2012;60:679-686.
NHAMCS: Does It Hold Up to Scrutiny? To the Editor: The Centers for Disease Control and Prevention’s (CDC’s) National Center for Health Statistics (NCHS) is committed to collecting and disseminating high-quality data that meet the information needs of a wide range of users. We take issue with the unfavorable assessment of National Hospital Ambulatory Medical Care Survey (NHAMCS) data in a recent editorial by Cooper1 and appreciate the opportunity to respond to her comments. We agree with Cooper1 that research findings need to be critically assessed, and we appreciate the guidelines she provides for potential authors using NHAMCS data, which are consistent with our recent article.2 We are troubled, however, by her sweeping indictment of the NHAMCS data-gathering process and her concern that medical practice or policy may have changed based on “the false assumption that the data were valid.”1 In fact, the authors cited by Cooper1 appropriately assessed the limitations of using NHAMCS data3-6 and reported that their findings3-5 were consistent with previous research. In cases in which findings from studies diverge, it is important to consider the methodology of each study. A particular strength of NHAMCS is that it includes hospitals other than academic medical centers, which commonly serve as the settings for research studies, thereby giving a more complete picture of health care use patterns. When comparing data from NHAMCS with other studies, one should always be careful to keep such methodological differences in mind before making conclusions about validity. Annals of Emergency Medicine 549