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Show Inpatient and Emergency Service Utilization in Patients With Idiopathic Intracranial Hypertension Jagger C. Koerner, BS, Deborah I. Friedman, MD, MPH Background: Many patients with idiopathic intracranial hypertension (IIH) are diagnosed in the emergency depart-ment (ED) or visit the ED during the course of their illness. We studied the use of inpatient and emergency services, determined what procedures and tests were provided at those encounters, evaluated how these variables changed over the study period and examined the coding validity of the International Classification of Diseases (ICD)-9 code for IIH (348.2) for adult patients seen in our affiliated EDs and inpatient services. Methods: Retrospective review of medical records over a 11-year period (2000-2011). Results: We were able to analyze 137 encounters from 51 patients. Sixty-eight percent of encounters were to the ED and 40% of those patients were subsequently admitted to the hospital. The most common symptoms were headaches (96%), vision change (53%), and photophobia (27%). Recurrent symptoms accounted for 43% of encounters, followed by surgical complications (26%) and initial pre-sentation (12%). Four patients (25% of the patients who received a diagnosis in the ED) were misdiagnosed at their initial presentation and correctly diagnosed on a subsequent ED visit. The number of ED visits more than doubled over the study period. The ICD-9 code had a low positive predictive value (55%) for identifying patients with IIH. Conclusions: The ED was commonly used by patients with IIH, with a mean of 2.7 visits per patient. The rate of a missed diagnosis was similar to another published series and is concerning for potentially permanent visual loss in undiagnosed patients. In our experience, the ICD-9 code vastly overestimated the number of ED and inpatient encounters attributable to IIH. This has important implica-tions for research studies, particularly those relying on national inpatient databases. Journal of Neuro-Ophthalmology 2014;34:229-232 doi: 10.1097/WNO.0000000000000073 © 2013 by North American Neuro-Ophthalmology Society Many patients with idiopathic intracranial hyperten-sion (IIH), particularly those with the most severe symptoms, are initially diagnosed and treated in an emer-gency department (ED) or inpatient setting. If surgery is required to control the intracranial pressure or treat visual loss, it is almost always performed on an inpatient basis (shunt procedure) or in an ambulatory surgery center (optic nerve sheath fenestration). Inpatient shunting procedures for IIH increased by 350% between 1988 and 2002 (1). How-ever, the use of inpatient and emergency services by patients with IIH previously has not been examined. The purpose of this study was to determine the coding validity of the Inter-national Classification of Diseases (ICD)-9 code (348.2) for IIH, record the use of inpatient and emergency services, determine what procedures and tests were provided at those encounters, and evaluate how these variables changed over the study period. METHODS Our protocol was approved by the Research Subjects Review Board at the University of Rochester (RSRB# 15754). Strong Memorial Hospital, Rochester, NY, inpatient and ED patient charts coded with a diagnosis of IIH, optic nerve sheath fen-estration, or lumbo-peritoneal (L-P) shunting, from August 1, 2000, to July 31, 2011, were selected for review. Children younger than 18 years were excluded. The ICD-9 code (348.2) for IIH identified 92 adult patients seen in the ED or inpatient setting over the search period. The procedure codes for optic nerve fenestration, and L-P shunting did not identify any additional IIH patients. Twenty-seven (30%) of the charts were initially excluded from further review. Of these, 15 charts (55%) were excluded University of Rochester (JCK), Rochester, New York; and Depart-ments of Neurology & Neurotherapeutics and Ophthalmology (DIF), University of Texas Southwestern Medical Center, Dallas, Texas. Supported by an unrestricted grant to the Department of Ophthal-mology, University of Rochester School of Medicine and Dentistry, Flaum Eye Institute. The authors report no conflicts of interest. Address correspondence to Deborah I. Friedman, MD, MPH, Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9036; E-mail: Deborah.Friedman@UTSouthwestern.edu Koerner and Friedman: J Neuro-Ophthalmol 2014; 34: 229-232 229 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. because there was no evidence of an IIH diagnosis or workup, 7 (26%) mentioned IIH in the medical history but provided no evidence of diagnosis or workup, and 5 (19%) were incomplete. There were 65 charts with evidence of IIH in adult patients seen in the ED or the inpatient setting. Of these, 14 did not meet our criteria for inclusion in the study. Patients presenting to the ED were included in the study when documentation supported the diagnosis of IIH consistent with the Friedman and Jacobson criteria (2). This included lumbar puncture (LP) pressure greater than 25 cm of cere-brospinal fluid (CSF) with normal CSF composition, nega-tive magnetic resonance imaging (MRI) or computed tomography (CT), and no other explanation for intracranial hypertension. Surgical patients were included when they had IIH in their medical history, surgery to treat IIH, or medical/ surgical visits to treat complications. The 51 patients identified averaged 2.7 encounters (ED or inpatient) each over the study period. Only encounters related to IIH were included in the study. ED patient visits were included when presenting symptoms, diagnosis, workup, and discharge information were consistent with IIH. The "possi-ble initial presentation" category (see below) is an exception for patients who presented with IIH symptoms, were not diagnosed or assessed for IIH, and at a subsequent encounter were evaluated and diagnosed with IIH. All surgery visits to treat IIH or complications from past surgeries were included. The total number of ED and inpatient encounters was 137. The following data were recorded: date of birth, age, race/ ethnicity, gender, date of encounter, body mass index (BMI), setting of encounter (ED, inpatient), presenting symptoms (headache, vision changes, syncope, emesis), length of stay, neuroimaging procedures [CT, MRI, magnetic resonance angiography, and magnetic resonance venography], surgical procedures (L-P shunt placement, removal, revision, optic nerve sheath fenestration), LP data (with or without fluoros-copy, opening pressure, amount of CSF removed), suspected cause, and possible undiagnosed initial encounter. RESULTS Patient data are summarized in Table 1. The female-to-male ratio was 25:1 (96% female). The average age was 33 years with a range of 19-59 years. The racial/ethnic breakdown of patients was generally consistent with the geographic area in which they lived, with 69% of the patients being Caucasian, 16% black, 6% Hispanic, and 10% unknown. The average BMI was 43.03 kg/m2 (n = 29). The BMI could not be calculated but obesity was noted in the chart in an additional 12 patients. Ten patients had no data regarding body habitus. The average LP opening pressure was 32.4 cm of CSF and a mean of 16.8 mL of CSF was removed. The majority (68%) of the 137 patient encounters were in the ED. Patients presented to the ED most commonly with headache (94%), vision changes (53%), photophobia (27%), emesis (17%), and syncope (9%). Three patients sought care in the ED for a post-lumbar puncture head-ache. A physician referral, most frequently from an ophthal-mologist, prompted 11 of the 93 ED visits. Of the ED visits, 40% resulted in hospital admission. Most patient encounters were the result of recurrent symptoms from IIH (43%), followed by surgical complications (26%) and initial presentation (12%). ED visits increased over the study period with a minimum of zero visits in 2001 and a maximum of 18 in 2009 (Fig. 1). Of the 3 patients only seen in the inpatient setting, 1 was admitted for elective LP shunt and 2 for headache symptoms. Shunt revision was the most common surgery, followed by L-P shunt placement. Over the study period, 8 L-P shunts were placed, 2 removed, and 10 revised. TABLE 1. Patient and demographic data Parameter No. of Patients (%) Race* Caucasian 35 (68) Black 8 (16) Unknown 5 (10) Hispanic 3 (6) Age, yr Average 33.3 Maximum 59 Minimum 19 Sex, n Female 49 (96) Male 2 (4) Body habitus Average BMI, kg/m2 43.0 Obese 12 LP pressure, cm of CSF Average opening 32.4 *2011 census data estimated the population in the greater Rochester New York area (Monroe County) to be 78% Caucasian, 16% black, and 7.5% Hispanic. CSF, cerebrospinal fluid; LP, lumbar puncture. FIG. 1. Emergency department visits for patients with idio-pathic intracranial hypertension. Asterisk indicates that only full calendar years are included. 230 Koerner and Friedman: J Neuro-Ophthalmol 2014; 34: 229-232 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. The positive predictive value (PPV) using our criteria for the diagnosis code 348.2 was 55% (51 of 92 patients were positively identified). IIH was recorded in 70% of patient encounters, and the average length of stay for inpatients was 3.9 days. The most common procedures followed by MRI were CT and LP. The use of CT, LP, and MRI (including magnetic resonance angiography and venography) did not increase on a per ED visit basis throughout the study, although the absolute number of the procedures increased as the number of ED visits rose. The number of these procedures and imaging studies per ED visit by year ranged from 0.9 to 2.3 with an average of 1.6 (Table 2). DISCUSSION The ICD-9 code for IIH had a low PPV (55%) in our study. This could partly be explained by the charts that mentioned IIH but lacked workup, possibly being incom-plete, and the several patients who left before the workup was complete. The largest group of charts excluded, however, did not mention IIH at all. Patients who were incorrectly coded with IIH had evidence in their chart of traumatic brain injury following motor vehicle accident, subdural hematoma, hydrocephalus, and neuroleptic malig-nant syndrome, among others. This suggests that the IIH code often is incorrectly used and is being assigned when intracranial hypertension is not idiopathic. This apparent overapplication of the code makes it difficult to compare data across institutions, and further research is needed to examine variability in coding validity. Assuming that the coding inaccuracies found at our institution are not unique to the University of Rochester, this has implications regarding research relying solely on national inpatient databases to study the impact of IIH (3). Patients previously diagnosed with IIH presenting with recurrent symptoms or complications from surgical proce-dures are a significant majority of IIH patients seen in the ED. Only 16 patients over the study period were newly diagnosed with IIH in the ED, making this a relatively rare occurrence given the 11-year study period. This study did not review outpatient data or data from other hospitals, and possibly, a subset of IIH patients only used outpatient services. Suspected cases of misdiagnosis in the ED are difficult to determine in a retrospective chart review study. Of the 16 patients initially diagnosed in the ED, 4 previously had presented with typical IIH symptoms and were diagnosed with IIH on a subsequent visit giving a mis-diagnosis rate of 25%. This is similar to a previous study of the initial IIH presentation in the ED that demonstrated a 27% misdiagnosis rate (4). Our misdiagnosis rate could be inaccurate as patients who presented to the hospital and received an alternative diagnosis may have sought care and subsequently been diagnosed with IIH as an outpatient or at another institution. Nearly all the patients who underwent surgery were also seen in the ED with complications from surgical procedures being the second greatest reason for an encounter (26%). Shunt malfunction or infection was noted as a suspected diagnosis in 11 of the 93 ED patient encounters. These visits resulted in 3 admissions for shunt revision and 1 recommendation to have the shunt revised at a later time, although in the remainder no evidence of shunt malfunc-tion was found. None of the surgical procedure codes revealed any patients that were improperly coded. Use of the ED increased over the study period. Given our study limitations, it is difficult to explore why this occurred and the increase could have been due to a variety of factors, including change in local referral patterns, increasing inci-dence of IIH, increased use of the ED generally, and growth driven by increased numbers of shunts placed over time (1). Our study is limited because it was performed in a single center. It is possible that some ED and inpatient visits were missed by our methods, as the search terms were selected to identify patients having encounters related to IIH. We were unable to verify whether our patients also sought care in nonaffiliated hospitals. Nonetheless, our findings suggest that the ED is frequently used by patients with recurring symptoms and complications from surgery. Many surgery patients use the ED at some point, and patients who use the ED typically presented multiple times. Initial diagnosis of IIH in the ED was infrequent and misdiagnosis of IIH occurred in approximately 25% of patients in our series, emphasizing the importance of funduscopy and a high index of suspicion to prevent delays in treatment and possible irreversible visual loss. Many patients with IIH presenting to the ED subsequently are admitted to hospital and suspected complications from surgery is the second most common reason for presentation to the ED. Lumbo-peritoneal shunts were performed more frequently for IIH TABLE 2. Frequency of neuroimaging studies and lumbar punctures, during the study period Year CT LP* MRI† Total ED Visits Ratio‡ 2002 4 4 6 14 6 2.3 2003 4 5 1 10 11 0.9 2004 3 2 2 7 5 1.4 2005 5 6 1 12 11 1.1 2006 6 9 2 17 13 1.3 2007 7 4 2 13 8 1.6 2008 11 8 8 27 12 2.3 2009 12 12 4 28 18 1.6 2010 5 11 10 26 13 2.0 *LP and LP under fluoroscopy. †Includes MRI, MVA, and MRV. ‡Number of procedures and imaging studies per ED visit. CT, computed tomography; ED, emergency department; LP, lumbar puncture; MRA, magnetic resonance angiography; MRI, magnetic resonance imaging; MRV, magnetic resonance venography. Koerner and Friedman: J Neuro-Ophthalmol 2014; 34: 229-232 231 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. in the Rochester area at the time our study, and L-P shunts are more prone to failure than ventriculoperitoneal shunts (5). It is possible that shunt-related admissions may be lower in hospitals where ventriculoperitoneal shunts are the preferred CSF diversion procedure. The ICD code 348.2 does not reliably identify patients with IIH, and using this code in isolation without a chart review likely overestimates the number of encounters for IIH in the ED and inpatient settings. REFERENCES 1. Curry WT, Butler WE, Barker IFG. Rapidly rising incidence of cerebrospinal fluid shunting procedures for idiopathic intracranial hypertension in the United States, 1988-2002. Neurosurgery. 2005;57:97-108. 2. Friedman DI, Jacobson DM. Diagnostic criteria for idiopathic intracranial hypertension. Neurology. 2002;59:1492-1495. 3. Friesner D, Rosenman R, Lobb BM, Tanne E. Idiopathic intracranial hypertension in the, USA: the role of obesity in establishing prevalence and healthcare costs. Obesity Rev. 2011;12:e372-e380. 4. Jones JS, Nevai J, Freeman MP, McNinch DE. Emergency department presentation of idiopathic intracranial hypertension. Am J Emerg Med. 1999;17:517-521. 5. McGirt MJ, Woodworth G, Thomas G, Miller N, et al. Cerebrospinal fluid shunt, placement for pseudotumor cerebri-associated intractable headache: predictors of, treatment response and an analysis of long-term outcomes. 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