Use of clinical classifications software to address ICD coding transition in large healthcare databases analyzed via high-dimensional propensity scores.

PURPOSE: The EUPAS26595 study characterized the rate of acute renal failure (ARF) in patients exposed to levetiracetam versus other antiepileptic drugs using healthcare claims data and a high-dimensional propensity score (hd-PS) for confounding adjustment. The data contained several coding systems by design and an update in International Classification of Diseases (ICD) coding dictionary. Such coding heterogeneity can affect the performance of hd-PS, and manually coding harmonization is not feasible. Our objective was to explore the impact of code aggregation via Clinical Classifications Software (CCS) on the analysis of a large claims-based database using hd-PS. METHODS: Patients with epilepsy, who were new-users of an antiepileptic drug, were identified from the IBM® MarketScan® Research Databases. We used CCS categories to harmonize coding and compared the results with other alternatives. Incidence rate ratios (IRRs) were computed using modified Poisson regression model with a robust variance estimator. RESULTS: For January 2008-October 2015 (before ICD update), 34 833 eligible patients initiated levetiracetam and 52 649 initiated a comparator drug; IRR (95% CI) for ARF for the hd-PS analysis was 1.34 (0.72-2.50) without CCS categories and 1.30 (0.71-2.39) with CCS categories. For January 2008-December 2017 (including ICD coding change), 45 672 eligible patients initiated levetiracetam and 64 664 initiated a comparator drug; IRR (95% CI) for the hd-PS analysis was 1.34 (0.78-2.29) without CCS categories and 1.37 (0.80-2.34) with CCS categories. CONCLUSIONS: Using single-level CCS categories to overcome differences in coding provides consistent results and can be used in studies that use large claims data and hd-PS for adjustment.

Safety of intravenous lacosamide in hospitalized children and neonates.

OBJECTIVE: Seizures are common in critically ill children and neonates, and these patients would benefit from intravenous (IV) antiseizure medications with few adverse effects. We aimed to assess the safety profile of IV lacosamide (LCM) among children and neonates. METHODS: This retrospective multicenter cohort study examined the safety of IV LCM use in 686 children and 28 neonates who received care between January 2009 and February 2020. RESULTS: Adverse events (AEs) were attributed to LCM in only 1.5% (10 of 686) of children, including rash (n = 3, .4%), somnolence (n = 2, .3%), and bradycardia, prolonged QT interval, pancreatitis, vomiting, and nystagmus (n = 1, .1% each). There were no AEs attributed to LCM in the neonates. Across all 714 pediatric patients, treatment-emergent AEs occurring in >1% of patients included rash, bradycardia, somnolence, tachycardia, vomiting, feeling agitated, cardiac arrest, tachyarrhythmia, low blood pressure, hypertension, decreased appetite, diarrhea, delirium, and gait disturbance. There were no reports of PR interval prolongation or severe cutaneous adverse reactions. When comparing children who received a recommended versus a higher than recommended initial dose of IV LCM, there was a twofold increase in the risk of rash in the higher dose cohort (adjusted incidence rate ratio = 2.11, 95% confidence interval = 1.02-4.38). SIGNIFICANCE: This large observational study provides novel evidence demonstrating the tolerability of IV LCM in children and neonates.

Poststroke epilepsy incidence, risk factors and treatment: German claims analysis.

OBJECTIVES: To describe incidence, risk factors, and treatment of poststroke epilepsy (PSE) in Germany based on claims data. METHODS: Retrospective analysis of claims data from a German public sickness fund (AOK PLUS). Patients with acute stroke hospitalizations from January 01, 2011 and December 31, 2015 (index hospitalization) were followed for 12-72 months. Outcomes included incidence of PSE (patients with ≥2 seizure claims [during/after index hospitalization], or ≥1 seizure claim after index hospitalization), multivariate Cox-regression analyses of time to seizure claim and death after index stroke hospitalization discharge, and antiepileptic drug (AED) treatment. RESULTS: Among 53 883 patients with stroke (mean follow-up of 829.05 days [median 749]), 6054 (11.24%) had ≥1 seizure claim (mean age 73.95 years, 54.18% female). 2130 (35.18%) patients had a seizure claim during index hospitalization (indicative of acute symptomatic seizures). Estimated incidence of PSE (cases/1000 patient-years) was 94.49 within 1 year. Risk of seizure claim following hospital discharge was higher in patients with hemorrhagic stroke (hazard ratio [HR] =1.13; p <.001) vs those with cerebral infarction. Seizure claim during index hospitalization was a risk factor for seizure claims after hospital discharge (HR =6.97; p <.001) and early death (HR =1.78; p <.001). In the first year of follow-up, AEDs were prescribed in 73.75% of patients with seizure claims. CONCLUSIONS: Incidence of PSE was in line with previous studies. Hemorrhagic stroke and seizure claim during index hospitalization were risk factors for seizure claims after hospital discharge. Most patients with seizure claims received AED treatment.

Dementia prevalence and incidence in a federation of European Electronic Health Record databases: The European Medical Informatics Framework resource.

INTRODUCTION: The European Medical Information Framework consortium has assembled electronic health record (EHR) databases for dementia research. We calculated dementia prevalence and incidence in 25 million persons from 2004 to 2012. METHODS: Six EHR databases (three primary care and three secondary care) from five countries were interrogated. Dementia was ascertained by consensus harmonization of clinical/diagnostic codes. Annual period prevalences and incidences by age and gender were calculated and meta-analyzed. RESULTS: The six databases contained 138,625 dementia cases. Age-specific prevalences were around 30% of published estimates from community samples and incidences were around 50%. Pooled prevalences had increased from 2004 to 2012 in all age groups but pooled incidences only after age 75 years. Associations with age and gender were stable over time. DISCUSSION: The European Medical Information Framework initiative supports EHR data on unprecedented number of people with dementia. Age-specific prevalences and incidences mirror estimates from community samples in pattern at levels that are lower but increasing over time.

Morbidity and medication in a large population of individuals with Down syndrome compared to the general population.

AIM: The aim of this study was to describe the incidence of morbidities and the prevalence of medical prescriptions in a large Down syndrome population. METHOD: A retrospective cohort study was carried out using the UK Clinical Practice Research Datalink from 1 January 2004 to 31 December 2013. We matched individuals with Down syndrome to randomly selected control participants by practice site, sex, birth year, and recording period. RESULTS: A total of 6430 individuals with Down syndrome (3009 females, 3421 males) and 19 176 controls (8966 females, 10,210 males) were included in the study. The incidence of cardiovascular disorders, gastrointestinal diseases (incidence rate ratio [IRR] 7.9 at 3 to <6y: yearly prevalence ratio [YPR] for laxatives 4.7), and sleeping disorders (IRR 4.8 in 3 to <6y) was increased in children with Down syndrome versus control participants. New onset of congenital heart malformation, ear diseases, eye disorders, autism, hypothyroidism, diabetes, and obesity were more frequent in childhood and remained elevated in adulthood (overall IRR 35.5, 1.7, 3.1, 4.4, 13.1, 1.3, and 2.6 respectively), whereas the gap widened in adulthood for epilepsy and intellectual disability (IRR 15.2 and 158 respectively, in participants older than 30y). At ≥ 30 years, the incidence of hypotension and dementia was raised (IRR 3.0 and 92.1 respectively; YPR for dementia drugs: 76.3); and that of hypertension, depression and anxiety was lowered (IRR 0.2, 0.5, and 0.4 respectively). INTERPRETATION: The profile of newly occurring morbidities in Down syndrome varies across the developmental lifespan.

Prevalence of cerebral amyloid pathology in persons without dementia: a meta-analysis.

IMPORTANCE: Cerebral amyloid-ß aggregation is an early pathological event in Alzheimer disease (AD), starting decades before dementia onset. Estimates of the prevalence of amyloid pathology in persons without dementia are needed to understand the development of AD and to design prevention studies. OBJECTIVE: To use individual participant data meta-analysis to estimate the prevalence of amyloid pathology as measured with biomarkers in participants with normal cognition, subjective cognitive impairment (SCI), or mild cognitive impairment (MCI). DATA SOURCES: Relevant biomarker studies identified by searching studies published before April 2015 using the MEDLINE and Web of Science databases and through personal communication with investigators. STUDY SELECTION: Studies were included if they provided individual participant data for participants without dementia and used an a priori defined cutoff for amyloid positivity. DATA EXTRACTION AND SYNTHESIS: Individual records were provided for 2914 participants with normal cognition, 697 with SCI, and 3972 with MCI aged 18 to 100 years from 55 studies. MAIN OUTCOMES AND MEASURES: Prevalence of amyloid pathology on positron emission tomography or in cerebrospinal fluid according to AD risk factors (age, apolipoprotein E [APOE] genotype, sex, and education) estimated by generalized estimating equations. RESULTS: The prevalence of amyloid pathology increased from age 50 to 90 years from 10% (95% CI, 8%-13%) to 44% (95% CI, 37%-51%) among participants with normal cognition; from 12% (95% CI, 8%-18%) to 43% (95% CI, 32%-55%) among patients with SCI; and from 27% (95% CI, 23%-32%) to 71% (95% CI, 66%-76%) among patients with MCI. APOE-ε4 carriers had 2 to 3 times higher prevalence estimates than noncarriers. The age at which 15% of the participants with normal cognition were amyloid positive was approximately 40 years for APOE ε4ε4 carriers, 50 years for ε2ε4 carriers, 55 years for ε3ε4 carriers, 65 years for ε3ε3 carriers, and 95 years for ε2ε3 carriers. Amyloid positivity was more common in highly educated participants but not associated with sex or biomarker modality. CONCLUSIONS AND RELEVANCE: Among persons without dementia, the prevalence of cerebral amyloid pathology as determined by positron emission tomography or cerebrospinal fluid findings was associated with age, APOE genotype, and presence of cognitive impairment. These findings suggest a 20- to 30-year interval between first development of amyloid positivity and onset of dementia.

Retrospective Multicenter Cohort Study on Safety and Electroencephalographic Response to Lacosamide for Neonatal Seizures.

BACKGROUND: There is growing evidence supporting the safety and effectiveness of lacosamide in older children. However, minimal data are available for neonates. We aimed to determine the incidence of adverse events associated with lacosamide use and explore the electroencephalographic seizure response to lacosamide in neonates. METHODS: A retrospective cohort study was conducted using data from seven pediatric hospitals from January 2009 to February 2020. For safety outcomes, neonates were followed for ≤30 days from index date. Electroencephalographic response of lacosamide was evaluated based on electroencephalographic reports for ≤3 days. RESULTS: Among 47 neonates, 98% received the first lacosamide dose in the intensive care units. During the median follow-up of 12 days, 19% of neonates died, and the crude incidence rate per 1000 patient-days (95% confidence interval) of the adverse events by diagnostic categories ranged from 2.8 (0.3, 10.2) for blood or lymphatic system disorders and nervous system disorders to 10.5 (4.2, 21.6) for cardiac disorders. Electroencephalographic seizures were observed in 31 of 34 patients with available electroencephalographic data on the index date. There was seizure improvement in 29% of neonates on day 1 and also in 29% of neonates on day 2. On day 3, there was no change in 50% of neonates and unknown change in 50% of neonates. CONCLUSIONS: The results are reassuring regarding the safety of lacosamide in neonates. Although some neonates had fewer seizures after lacosamide administration, the lack of a comparator arm and reliance on qualitative statements in electroencephalographic reports limit the preliminary efficacy results.

Epidemiology of focal onset seizures in children aged >1 month to 4 years in Europe, United States, and Canada: A literature review.

The present study aims to report the currently available epidemiology of focal onset seizures in children aged >1 month to 4 years with the help of a literature review. The terms 'seizure*' OR 'epilepsy' combined with pediatric and epidemiology terms were used to search Embase, PubMed, and Web of Science up to November 16, 2021. Due to the scarcity of epidemiology data on focal onset seizures, the incidence and prevalence were estimated using the proportion of focal onset seizures in epilepsy patients from the most recently published articles. The estimated annual incidence per 100,000 children of focal onset seizures in children of 0-4 years of age ranged from 25.1 (95 % confidence interval [CI] 18.9-32.7) in the United Kingdom to 111.8 in the United States. The estimated period prevalence of focal onset seizures in children 0-4 years of age ranged from 0.15 % (99 % CI 0.13-0.18) in Canada to 0.61 % in the United States. Neurodevelopmental outcomes and psychiatric disorders were the most commonly reported comorbidities in children with epilepsy of age 0-4 years. Presence of focal onset seizures in children with different epilepsy syndromes needs to be thoroughly considered in the treatment planning of this population of interest.

Epidemiology, real-world treatment and mortality of patients with status epilepticus in Germany: insights from a large healthcare database.

Status epilepticus is a life-threatening emergency, and to date, few studies have reported on its long-term treatment and outcomes. This study aimed to estimate the incidence, the treatment and outcomes, the healthcare resource utilization and the costs of status epilepticus in Germany. Data from 2015 to 2019 were obtained from German claims (AOK PLUS). Patients with ≥1 status epilepticus event and no event in the preceding 12 months (baseline) were included. A subgroup of patients with an epilepsy diagnosis during baseline was also analysed. Of the 2782 status epilepticus patients (mean age = 64.3 years; 52.3% female), 1585 (57.0%) were previously diagnosed with epilepsy. The age- and sex-standardized incidence was 25.5 cases/100 000 persons in 2019. The mortality rate after 12 months was 39.8% overall (19.4% and 28.2% after 30 and 90 days, respectively) and 30.4% in the epilepsy patient subgroup. Factors associated with higher mortality were age, comorbidity status, presence of brain tumours and an acute stroke. An epilepsy-related hospitalization at onset of or 7 days prior to the status epilepticus event as well as prescription of antiseizure medication during baseline was associated with a better survival rate. Overall, 71.6% of patients (85.6% in the epilepsy subgroup) were prescribed with out-patient antiseizure medication and/or rescue medication within 12 months. All patients sustained on average 1.3 status epilepticus-related hospitalizations (20.5% had more than one) during a mean follow-up period of 545.2 days (median 514 days); total direct costs including in-patient and out-patient status epilepticus treatments were 10 826€ and 7701€ per patient-year overall and for the epilepsy patient subgroup, respectively. The majority of status epilepticus patients received an out-patient treatment in line with epilepsy guidelines, and patients previously diagnosed with epilepsy have a higher likelihood to receive it. The mortality in the affected patient population is high; risk factors were older age, higher comorbidity burden, the presence of brain tumours or an acute stroke.

Incidence of Acute Renal Failure in Patients Using Levetiracetam Versus Other Antiseizure Medications: A Voluntary Post-Authorization Safety Study.

INTRODUCTION: Acute kidney injury is an expected adverse drug reaction listed in the European Union (EU) Summary of Product Characteristics (SmPC) for levetiracetam, one of the most widely used modern antiseizure medications (ASMs). OBJECTIVE: We conducted a voluntary post-authorization safety study to characterize the rate of acute renal failure (ARF) in patients exposed to levetiracetam versus other ASMs. METHODS: New users of ASMs without prior renal dysfunction were identified and followed for 30 days in the IBM® MarketScan® database (USA, January 2008-December 2017). ARF was defined as a diagnosis on inpatient or emergency department claims. We estimated adjusted incidence rates, incidence rate ratios (IRRs), and incidence rate differences (IRDs) of ARF in patients initiating levetiracetam versus other ASMs. RESULTS: Overall, 110,336 patients were eligible for the monotherapy cohort and 96,215 were eligible for the polytherapy cohort. The overall crude rate of ARF following a new ASM was 6.0 and 6.5 per 10,000 patients for the 'monotherapy' and 'polytherapy' cohorts, respectively, in the first 30 days after the index date. In the monotherapy cohort, the IRR for ARF was 1.37 (95% confidence interval [CI] 0.80-2.34) and the corresponding IRD was 2.0 (95% CI - 1.12 to 5.12) additional ARFs per 10,000 patient-months. In the polytherapy cohort, the adjusted IRR for ARF was 0.94 (95% CI 0.51-1.74) and the corresponding IRD was - 0.42 cases per 10,000 patient-months (95% CI - 4.01 to 3.17). CONCLUSIONS: The rate of ARFs in ASM new users was very low. In patients without prior ASMs, the estimated difference in risk of ARF associated with initiation of levetiracetam versus initiation of other ASMs was small, with 95% CIs compatible with small protective or harmful effects. In patients receiving polytherapy, the difference was compatible with the null and the 95% CI with small protective or harmful effects.

Thrombosis with thrombocytopenia after AZD1222 (ChAdOx1 nCov-19) vaccination: Case characteristics and associations.

BACKGROUND: Post-marketing surveillance for COVID-19 vaccines during the pandemic identified an extremely rare thrombosis with thrombocytopenia syndrome (TTS) reported post-vaccination, requiring further characterisation to improve diagnosis and management. METHODS: We searched the AstraZeneca Global Safety Database (through April 26, 2021) for cases with co-reported thrombocytopenia and thrombosis (using standardised MedDRA queries/high-level terms) following AZD1222 (ChAdOx1 nCoV-19). Cases were adjudicated by experts as 'typical','possible', 'no' or 'unknown' according to available TTS criteria. Additional confirmatory datasets (May 20-June 20, October 1-December 28) were evaluated. FINDINGS: We identified 573 reports, including 273 (47.6 %) 'typical' and 171 (29.8 %) 'possible' TTS cases. Of these 444 cases, 275 (61.9 %) were female, median age was 50.0 years (IQR: 38.0-60.0). Cerebral venous sinus thrombosis was reported in 196 (44.1 %) cases, splanchnic venous thrombosis in 65 (14.6 %) and thromboses at multiple sites in 119 (26.8 %). Median time to onset was 12.0 days (IQR: 9.0-15.0). Comparison with a pre-pandemic reference population indicated higher rates of autoimmune disorders (13.8 %, 4.4 %), previous heparin therapy (7.4 %, 1.2 %), history of thrombosis (5.5 %, 1.4 %), and immune thrombocytopenia (6.1 %, 0.2 %). Fatality rate was 22.2 % (127/573) overall and 23.6 % (105/444) in 'typical'/'possible' TTS, which decreased from 39.0 % (60/154) in February/March to 15.5 % (45/290) in April. Overall patterns were similar in confirmatory datasets. CONCLUSIONS: The reporting rate of 'typical'/'possible' TTS post first-dose vaccination in this dataset is 7.5 per million vaccinated persons; few cases were reported after subsequent doses, including booster doses. Peak reporting coincided with media-driven attention. Medical history differences versus a reference population indicate potentially unidentified risk factors. The decreasing fatality rate correlates with increasing awareness and publication of diagnostic/treatment guidelines. Adjudication was hindered by unreported parameters, and an algorithm was developed to classify potential TTS cases; comprehensive reporting could help further improve definition and management of this extremely rare syndrome.

Real-world data on the incidence, mortality, and cost of ischaemic stroke and major bleeding events among non-valvular atrial fibrillation patients in England.

RATIONALE, AIMS, AND OBJECTIVES: Several novel oral anticoagulants (NOACs) are licensed for atrial fibrillation (AF) treatment in the United Kingdom. We describe the incidence and mortality from ischaemic stroke and major bleeding in non-valvular atrial fibrillation (NVAF) patients in England, including treatment patterns before/following introduction of NOACs, healthcare resource utilization (HRU), and costs post-onset of these events. METHOD: Data were extracted from the UK Clinical Practice Research Datalink linked to Hospital Episode Statistics secondary care and Office for National Statistics mortality data. RESULTS: Of 42 966 patients with a first AF record between 2011 and 2016, 9143 patients (21.3%) remained without AF (antiplatelets/antithrombotics) treatment post-index diagnosis. The proportion of patients receiving aspirin for ≥3 months post-index declined during the study (50.6%-5.5%), irrespective of CHA2 DS2 -VASc score, while the proportion prescribed NOACs increased (2.0%-70.1%). Rates of ischaemic stroke per 1000 patient-years (95% CI) were 9.4 (3.8-15.0) with NOACs, 10.4 (8.0-12.9) with warfarin, 20.1 (16.4-23.8) with aspirin, 21.3 (5.3-37.2) with other antiplatelets and 43.6 (39.3-47.8) in patients without AF prescription. Major bleeding occurred at a similar rate with different treatments. All-cause mortality rates were 42.8 (31.4-54.3) with NOACs, 46.3 (41.1-51.5) with warfarin, 56.5 (50.5-62.4) with aspirin, 102.2 (76.2-128.3) with other antiplatelets and 412.8 (399.6-426.0) with no AF prescription. Mean annual National Health Service healthcare costs up to 1 year post-index were lowest in patients receiving aspirin plus other antiplatelets without an event (£6152), and highest in patients with an event without AF prescriptions (£17 957). By extrapolation, national AF HRU in the United Kingdom in 2016 was estimated at £8-16 billion annually. CONCLUSIONS: These data provide temporal insights into AF treatment patterns and outcomes for NVAF patients in England and highlight the need to review higher stroke risk AF patients not receiving antiplatelet/antithrombotic prescriptions.

Risk of Upper Gastrointestinal Bleeding and Gastroduodenal Ulcers in Persons With Schizophrenia: A Danish Cohort Study.

INTRODUCTION: There is little evidence about gastrointestinal (GI) disorders in patients with schizophrenia. We examined association of schizophrenia with upper GI bleeding (UGIB) and nonbleeding ulcers and associated risk factors and mortality. METHODS: We used the data linked from population-based registries in Denmark. Among patients with incident schizophrenia in 1980-2011, we computed cumulative incidences and standardized incidence ratios of UGIB, bleeding ulcers, and nonbleeding ulcers compared with the general population; evaluated risk factors for the 3 GI endpoints, including somatic and psychiatric comorbidity; and examined subsequent all-cause mortality. RESULTS: Among 39,998 patients with schizophrenia, the standardized incidence ratios were 2.92 (95% confidence interval (CI), 2.76-3.08) for UGIB, 2.36 (95% CI, 2.15-2.58) for bleeding ulcers, and 2.00 (95% CI, 1.87-2.15) for nonbleeding ulcers. Risk factors for UGIB and nonbleeding ulcers included age, somatic comorbidity, and medication use. UGIB and nonbleeding ulcers were associated with the subsequent increase in mortality. CONCLUSIONS: Schizophrenia is associated with an increased risk of UGIB and nonbleeding ulcers, whose risk factors in patients with schizophrenia are similar to those in the general population.

Multiple Sclerosis and Risk of Infection-Related Hospitalization and Death in US Veterans.

BACKGROUND: This study estimated the risk of infection-related hospitalizations and death in patients with and without multiple sclerosis (MS). METHODS: We identified adults with MS in the US Department of Veterans Affairs (VA) system between 1999 and 2010. Each veteran with MS was matched, on age and sex, with up to four veterans without MS. Multivariable Cox proportional hazards regression models were performed to assess the influence of MS on the development of serious and fatal infections. RESULTS: The cohort included 7743 veterans with MS and 30,972 veterans without MS. Mean (SD) age was 53.8 (13.3) years, and 80.8% were male. The incidence per 1000 person-years of overall serious infections was 19.2 (95% confidence interval [CI], 17.6-20.8) for those with MS and 10.3 (95% CI, 9.8-10.9) for those without MS. Fatal infection incidence rates were 1.2 (95% CI, 0.8-1.7) for patients with MS and 0.5 (95% CI, 0.3-0.6) for patients without MS. Regression models showed that veterans with MS were at greater risk for overall serious (hazard ratio [HR] = 1.52, P < .01) and fatal (HR = 1.85, P = .03) infections and serious respiratory (HR = 1.31, P = .01), urinary tract (HR = 4.44, P < .01), and sepsis-related infections (HR = 2.56, P < .01). CONCLUSIONS: This study provides evidence that VA patients with MS are more likely than those without MS to be hospitalized and die of infection.

Age-Stratified Prevalence of Mild Cognitive Impairment and Dementia in European Populations: A Systematic Review.

The prevalence of mild cognitive impairment (MCI) and dementia according to age remain uncertain. We systematically extracted age-stratified estimates of MCI and dementia prevalence reported in European studies published since 1995, and performed meta-analyses for dementia. We identified 10 relevant studies on MCI and 26 studies on dementia. Studies on MCI presented substantial heterogeneity preventing a meta-analysis, with a majority reporting an increase in prevalence at ≥75 years old. Pooled prevalence of dementia rose continuously from 55 years of age, reaching 44.7% (39.8; 49.6) in those ≥95 years of age. Homogenization of MCI criteria, and additional studies in Northern European population would be warranted.

Negative symptoms in schizophrenia: a study in a large clinical sample of patients using a novel automated method.

OBJECTIVES: To identify negative symptoms in the clinical records of a large sample of patients with schizophrenia using natural language processing and assess their relationship with clinical outcomes. DESIGN: Observational study using an anonymised electronic health record case register. SETTING: South London and Maudsley NHS Trust (SLaM), a large provider of inpatient and community mental healthcare in the UK. PARTICIPANTS: 7678 patients with schizophrenia receiving care during 2011. MAIN OUTCOME MEASURES: Hospital admission, readmission and duration of admission. RESULTS: 10 different negative symptoms were ascertained with precision statistics above 0.80. 41% of patients had 2 or more negative symptoms. Negative symptoms were associated with younger age, male gender and single marital status, and with increased likelihood of hospital admission (OR 1.24, 95% CI 1.10 to 1.39), longer duration of admission (ß-coefficient 20.5 days, 7.6-33.5), and increased likelihood of readmission following discharge (OR 1.58, 1.28 to 1.95). CONCLUSIONS: Negative symptoms were common and associated with adverse clinical outcomes, consistent with evidence that these symptoms account for much of the disability associated with schizophrenia. Natural language processing provides a means of conducting research in large representative samples of patients, using data recorded during routine clinical practice.