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Original Research: Diffuse Lung Disease |

The Increasing Secondary Care Burden of Idiopathic Pulmonary FibrosisSecondary Care Burden of IPF: Hospital Admission Trends in England From 1998 to 2010 FREE TO VIEW

Vidya Navaratnam, BMBS; Andrew W. Fogarty, MBBS, PhD; Rachel Glendening; Tricia McKeever, PhD; Richard B. Hubbard, MBBS, PhD
Author and Funding Information

From the Division of Epidemiology and Public Health (Drs Navaratnam, Fogarty, McKeever, and Hubbard and Ms Glendening), University of Nottingham; and Nottingham Respiratory Research Unit, Nottingham City Hospital (Dr Navaratnam), Nottingham, England.

Correspondence to: Vidya Navaratnam, BMBS, Division of Respiratory Medicine, Clinical Sciences Bldg, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB, England; e-mail: vidya.navaratnam@nottingham.ac.uk


Funding/Support: Dr Navaratnam is funded by a research grant from the Medical Research Council. Dr Hubbard is funded by the GlaxoSmithKline/British Lung Foundation chair of Epidemiological Respiratory Research.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2013;143(4):1078-1084. doi:10.1378/chest.12-0803
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Background:  The lack of mandatory clinical registries for idiopathic pulmonary fibrosis (IPF) has meant a reliance on routine clinical data to provide trends in disease incidence. Death certificate and primary care data suggest that the incidence of IPF has increased in the United Kingdom at a rate of approximately 5% per year, but due to possible concerns about the diagnostic validity of these clinical datasets, it is helpful also to analyze data from secondary care. We used national secondary care data to determine trends in hospital admissions for IPF clinical syndrome (IPF-CS) in England between 1998 and 2010.

Methods:  We obtained the annual number of hospital admissions for all National Health Service (NHS) hospital trusts in England for the International Classification of Diseases and Related Health Problems, 10th Revision codes J84.1 and J84.9 between 1998 and 2010. We calculated annual admission-rate ratios, adjusting for age and sex, using Poisson regression. We also investigated changes in age at admission and length of stay, and we estimated hospitalization costs.

Results:  The number of hospital admissions from IPF-CS increased at an annual rate of approximately 5%, from 5,524 patients in 1998 to 9,525 patients in 2010, and was highest in men and the older population. Mean age at admission increased from 66 to 71 years, while length of stay decreased by 2.1 days during the same period.

Conclusions:  Hospital admissions for IPF-CS in England follow a similar trend to other data sources in the United Kingdom. This has resulted in escalating costs of inpatient care, which is a significant financial burden on health-care resources.

Figures in this Article

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic lung disease with a similar prognosis to many malignancies and with a median survival of 3 years.1 Studies using general practice data in the United Kingdom and insurance data from the United States have suggested that the incidence of IPF is on the rise.15 This trend is consistent with data from registered death certificates in England and Wales,5 but to date there is no evidence of a similar increase of cases seen in secondary care. This has important implications in health-care planning and allocation of resources in order to provide inpatient care for these patients. Furthermore, there have been concerns about the diagnostic validity of general practice and death certificate data in observational studies of IPF. Therefore, there is also a need to analyze secondary care data to ensure consistency of the trends seen, as well as provide information about disease burden in this health sector.

The aim of this study was to use a national, secondary care dataset to determine the trend in hospital admissions for IPF in England between 1998 and 2010. We also investigated changes in length of stay (LOS) and patient age at time of admission, and estimated the financial impact of hospitalization on the National Health Service (NHS) in England in terms of number of bed days.

Data Collection

We used routinely available, national, inpatient data obtained from Hospital Episode Statistics (HES) from 1998 until 2010.6 The HES database contains information on all admissions to a NHS hospital in England, with >12 million new records added each year. All NHS hospitals in England are required to contribute to this database. The HES database is managed by the NHS Information Centre for health and social care and is available for research without ethics approval. The available data consist of a number of records for each admission, which are called episodes. Each episode represents the time period of an inpatient admission during which a patient was under the clinical care of a particular consultant team. Each episode contains diagnoses coded in the International Statistical Classification of Diseases and Related Health Problems, 10th Revision7 (ICD-10) related to the reason for hospital admission. We extracted the annual number of hospital admissions (ie, finished consultant episodes) stratified by age for the ICD-10 codes J84.1 (other interstitial pulmonary disease with fibrosis) and J84.9 (interstitial pulmonary disease, unspecified).7 These codes were used to capture individuals with fibrotic lung disease of unknown origin, the majority of which were IPF. As a small subset of people included in the dataset may not have had IPF as defined by the American Thoracic Society/European Respiratory Society diagnostic criteria,8 we labeled the individuals within our dataset as having clinical syndrome (IPF-CS). We also obtained data on total number of bed days, the proportion of patients who were male, and mean age of the patient group at time of admission each year. We used the total population from England for each year for the years 1998 to 2010 as our denominators.9

Statistical Analyses

For these analyses, the data on admissions and the general population were grouped into three age bands and each calendar period was based on a financial year. We calculated age and sex stratum-specific admission rates for each year and then applied these rates to the 2010 population to generate the annual standardized number of admissions. Poisson regression modeling was used to estimate annual admission-rate ratios with adjustment for sex and age. A multiplicative interaction term was used to test for effect modification between annual trends in admission-rate ratios of IPF-CS and age or sex.

We calculated an estimate of the average LOS by dividing the total number of bed days by the total number of admissions for each calendar period. Linear regression was used to test for changes in mean age at admission, number of bed days, and mean LOS. We calculated the cost of hospital admissions for IPF-CS in terms of bed days for each calendar period by multiplying the cost of a bed day in the NHS for the 2009-2010 financial year10 by the total number of bed days from both ICD-10 codes for each calendar period. Finally, we developed a multivariable Poisson regression model to predict future hospital-admission rates for IPF-CS for the year 2020 and calculated the cost of inpatient care in terms of bed days for that year without adjusting for inflation costs or change to market forces. Stata, version 11 (StataCorp LP) was used for all statistical analyses and hypothesis testing.

Between 1998 and 2010, there were 93,821 admissions coded as being due to other interstitial pulmonary diseases with fibrosis (ICD-10 code J84.1) and 12,627 admissions coded as being due to interstitial pulmonary disease, unspecified (ICD-10 code J84.9) in England. The number of recorded admissions increased from 5,544 (6,265 admissions after standardization to the 2010 population) in 1998 to 9,525 in 2010 for the ICD-10 code J84.1 and from 294 (320 admissions after standardization to the 2010 population) in 1998 to 2,280 in 2010 for the ICD-10 code J84.9 (Fig 1). The overall admission rate standardized to the 2010 population over this period was 14.95 per 100,000 person years (95% CI, 14.86-15.05) and 2.01 per 100,000 person years (95% CI, 1.98-2.05) for the ICD-10 codes J84.1 and J84.9, respectively. Admission rates for both ICD-10 codes were higher in men and the older population (Tables 1, 2). After controlling for the effects of age, we calculated that the overall year-on-year increase in admissions was approximately 5% (rate ratio, 1.05; 95% CI, 1.050-1.054) for ICD-10 code J84.1 and 20% (rate ratio, 1.20; 95% CI, 1.19-1.21) for ICD-10 code J84.9.

Figure Jump LinkFigure 1. Estimated number of admissions from idiopathic pulmonary fibrosis clinical syndrome, age standardized to the 2010 population of England. ICD-10 = International Classification of Diseases and Related Health Problems, 10th Revision.Grahic Jump Location
Table Graphic Jump Location
Table 1 —Crude Admission Rates and Poisson Regression Modeling of Hospital Admissions for IPF-CS

ICD-10 = International Classification of Diseases and Related Health Problems, 10th Revision; IPF-CS = idiopathic pulmonary fibrosis clinical syndrome.

a 

Admission-rate ratios are adjusted for age groups.

b 

P for trend < .0001.

Table Graphic Jump Location
Table 2 —Crude Admission Rates and Poisson Regression Modeling of Admissions of IPF-CS Stratified by Sex

See Table 1 legend for expansion of abbreviations.

a 

Admission rate ratios are adjusted for calendar period.

b 

Likelihood ratio test, P < .0001.

c 

Likelihood ratio test, P < .016.

The increase in admission rates over time was higher in the older population (P < .0001) for both ICD-10 codes. The age group-specific admission-rate ratios for the ICD-10 code J84.1 were 1.01 (95% CI, 1.01-1.02) for individuals aged ≤ 59 years, 1.03 (95% CI, 1.02-1.03) for individuals aged 60 to 74 years, and 1.07 (95% CI, 1.06-1.07) for those aged ≥ 75 years. For the ICD-10 code J84.9, the age group-specific admission-rate ratios were 1.15 (95% CI, 1.14-1.16) for individuals aged < 59 years, 1.20 (95% CI, 1.19-1.21) for individuals aged between 60 and 74 years, and 1.26 (95% CI, 1.24-1.27) for those aged > 75 years. There was no evidence of a statistical interaction to suggest that the increase in admission rates over time were higher in men for the ICD-10 code J84.1 (P = .0814). However, we found evidence of a statistical interaction for the ICD-10 code J84.9 that suggested the increasing admission rates over time were slightly higher in women (P < .0001), although the sex-specific, admission-rate ratios were similar, 1.19 (95% CI, 1.18-1.20) in men and 1.20 (95% CI, 1.19-1.21) in women.

We found that mean age at time of admission for both ICD-10 codes increased during the study period from 66 years in the 1998-1999 calendar period to 71 years in the 2009-2010 calendar period for the ICD-10 code J84.1 and from 49 years in the 1998-1999 calendar period to 63 years in the 2009-2010 calendar period for the ICD-10 code J84.9 (Table 3). We also found that the estimated average LOS declined from 7.2 days in the 1998-1999 calendar period to 5.1 days in the 2009-2010 calendar period for the ICD-10 code J84.1, and from 6.1 days in the 1998-1999 calendar period to 3.6 days in the 2009-2010 calendar period for the ICD-10 code J84.9 (Table 3). During the 12-year study period, the estimated financial burden on the NHS in England in terms of inpatient bed days from IPF-CS increased from £12 million to £16.2 million (Table 4). Using our multivariable Poisson regression model, we estimate that in the year 2020, there will be close to 20,000 hospital admissions from IPF-CS, which will cost health services almost £20 million.

Table Graphic Jump Location
Table 3 —Bed Days, Mean Length of Stay, and Mean Age at Time of Admission for Individuals With IPF-CS

See Table 1 legend for expansion of abbreviations.

a 

Linear regression, P < .0001.

Table Graphic Jump Location
Table 4 —Total Number of Bed Days and Associated Cost for IPF-CS

NHS = National Health Service. See Table 1 for expansion of other abbreviation.

a 

Linear regression, P = .004.

Using national data from secondary care activity, we found that the number of hospital admissions from IPF-CS is on the rise, which is in keeping with studies suggesting that the incidence of diagnosed IPF is increasing in the United Kingdom and the United States.1,35 The increase in hospital admissions for IPF-CS was approximately 5% per year, which is similar to that seen in general practice data and registered death certificates.5 We found that the increase in admissions from IPF-CS was higher in men and the older age groups, which is consistent with previous studies.13,5 We also found that mean age at admission increased during the study period and the estimated average LOS for each admission decreased. On the basis of our findings, we estimate that the financial burden from IPF-CS inpatient care alone in England is currently £16 million and will be almost £20 million by 2020, although this is likely to be an underestimation as it does not take into account changes to market forces and inflation costs.

This is the first study to use a national, secondary care dataset to determine trends in IPF hospital admissions in England. The dataset used is large and comprehensive; it encompasses all hospital admissions for IPF-CS in England, including specialist tertiary centers and district general hospitals. This has allowed us to provide a realistic estimate of disease burden without the bias that can occur with sampling. The large number of hospital admissions and long study period also permitted us to examine changes in average LOS in hospital and age at admission.

Our study has a number of limitations that require consideration. As we have used routinely recorded clinical data, the diagnosis of pulmonary fibrosis in these data is unlikely to involve a lung biopsy. However, this is in keeping with current clinical practice in the United Kingdom, where < 10% of people with IPF undergo a lung biopsy. Another limitation of these data is that they do not permit us to give more detailed, age-specific admission rates, which would help ascertain which age groups are more likely to be hospitalized. The third limitation of our study is the accuracy of diagnostic coding within our dataset. A previous study found the accuracy of diagnostic coding of hospital admissions for pulmonary fibrosis in England to be high.11 In addition, a systematic review found a 91% median accuracy in diagnostic coding of hospital admissions in England prior to our study period, and the most recent audit of selected samples of UK hospital data confirmed almost 90% accuracy in diagnostic coding.12 Furthermore, people with IPF usually have their diagnosis confirmed in secondary care, and hence individuals with a diagnosis of IPF in our dataset are likely to have the disease. There is a possibility, however, that some individuals with IPF who were admitted to hospital were not included in our dataset, and hence, our findings are more likely to be an underestimation of the actual burden of disease.

We used two ICD-10 codes to describe the impact of idiopathic, interstitial lung disease on secondary care services. The ICD-10 code J84.1 is likely to include those with diffuse pulmonary fibrosis, cryptogenic fibrosing alveolitis, Hamman-Rich syndrome, usual interstitial pneumonia, and IPF; ICD-10 code J84.9 may include people with a spectrum of fibrotic lung disease of unknown etiology. Despite the possibility of diagnostic imprecision within these data, we believe the majority of our cohort will have IPF. A study by Fell and colleagues13 showed that age is a strong predictor of IPF in patients with atypical radiographic appearances of usual interstitial pneumonia; they reported a 76% specificity of confirming IPF histologically in individuals aged > 60 years. The majority of the individuals assigned both ICD-10 codes were aged > 60 years, reaffirming our belief that most people included in our dataset have IPF.

There is also the possibility of coding errors between the two ICD-10 codes used. However, subanalysis of the individual ICD-10 codes showed similar trends, making it unlikely that the overall admission trends were due to diagnostic transfer in disease coding. There is also suggestion of improved accuracy of coding, given that the annual increase in hospital admissions for ICD-10 code J84.1 was consistent with our previous work looking at registered death certificates using the same ICD-10 code.5 We have been unable to identify patients who had more than one admission to hospital. However, we believe that repeated episodes of hospitalization would not be the main reason for the increase in admission trends seen. Our previous work suggests that the annual number of newly diagnosed cases of IPF-CS is similar as the number of deaths.5 Therefore, it is unlikely that the number of prevalent cases would increase significantly each year.

This study has demonstrated a similar annual increase in IPF-CS recordings to that found in registered death certificates and primary care data.5 This provides reassurance that the increasing trends are real and validates the use of routinely recorded clinical data in observational studies in IPF. It is unclear whether the observed increase in incidence represents a true increase or is due to other explanations. The increase in mean age at admission during our study period implies that ascertainment is an important factor and suggests that there may still be a considerable number of cases yet undiagnosed. Either way, the increasing number of hospital admissions translates into growing costs in inpatient care, which, in turn, have significant impact on health-care resources.

There is scarce information regarding LOS in hospital and cost of hospitalization for IPF. We believe these data will be useful in developing health-care pathways, aiding service delivery, and planning for the future cost of IPF inpatient care. Our projection of future inpatient costs is influenced by trends in increasing number of admissions and a reduction in LOS seen in the study. Due to IPF being a disease of the elderly with multiple comorbid illnesses,5,1416 it is possible that further reductions in LOS will not offset any increases in hospitalization rates, which would lead to spiraling costs. It is also important to recognize that our projections of inpatient care do not approximate the total cost of IPF to the health-care system, as we have not accounted for disease monitoring, and outpatient and social care costs. A study in the United States found a steady increase in the number of IPF hospital discharges over 15 years, reaching almost 33,500 discharges per year in 2008.17 These findings are not surprising, since previous studies using mortality data in the United States have demonstrated similar trends.18,19 Given that studies have shown that the incidences of IPF in the United Kingdom and the United States are similar,4,5 we have estimated that there will be close to 60,000 hospital admissions for IPF in the United States in the year 2020. Hospitalization costs for IPF in the United States increased almost fourfold from 1993 to 2008, and doubled between 2007 and 2008 to approximately $1.5 billion despite a reduction in hospital LOS.17,20 The mounting cost of hospitalization for IPF will exert significant financial pressure on health-care providers in the United States.

The decrease in average LOS during our study period could be related to the general trend of decreasing LOS in hospital and increased pressure within health-care services for earlier discharge. This trend in declining average LOS was also seen in IPF hospital admissions in the United States, where LOS decreased from 8 days in 1993 to 6 days in 2008,17 as well as in hospital admissions for other chronic respiratory conditions in England. For example, we found that people admitted to NHS hospitals with an acute exacerbation of COPD (ICD-10 code J44.1) during our study period had a reduction of 3.4 days in their average LOS in hospital despite being 7 years older at time of admission and more likely to have had more comorbidities. Studies have also shown that mechanical ventilation to treat respiratory failure does not alter the poor prognosis of this disease.21,22 This could be a reason for shorter LOS in hospital, with fewer patients being admitted to ICUs. It is also a possibility that the increased provision of specialized services at the frontline has resulted in people with IPF getting earlier specialist care and access to home oxygen, and in discharge schemes with increased primary care support on returning home. With the increasing number of inpatients and associated financial burden on health-care providers, which is projected to increase in the foreseeable future, it is essential that measures to prevent unnecessary hospitalization are put in place. With no effective pharmacologic interventions that prolong survival in IPF, there is a pressing need to improve community-based palliative care services and integration with primary care to achieve symptom control and end-of-life care for these patients.

In summary, using secondary care data, we have shown that hospital admissions for IPF-CS are increasing at the same rate as general practice and death certificate recordings. The combined costs of inpatient care, regular outpatient review, and monitoring of disease severity for these individuals poses a significant financial burden on health-care services worldwide.

Authors contributions: Dr Navaratnam takes responsibility for the integrity of the work in this manuscript and is the guarantor of the manuscript.

Dr Navaratnam: contributed to conception and design of the study; data acquisition, analysis, and interpretation; and writing or revising the manuscript before submission and served as principal author.

Dr Fogarty: contributed to study conception and design, data interpretation, and writing or revising the manuscript before submission.

Ms Glendening: contributed to data acquisition, analysis, and interpretation and writing or revising the manuscript before submission.

Dr McKeever: contributed to data analysis and interpretation and writing or revising the manuscript before submission.

Dr Hubbard: contributed to study conception and design, data acquisition and interpretation, and writing or revising the manuscript before submission.

Financial/nonfinancial disclosure: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Role of sponsors: The sponsor had no role in the design of the study, the collection and analysis of the data, or in the preparation of the manuscript.

HES

Hospital Episode Statistics

ICD-10

International Classification of Diseases and Related Health Problems, 10th Revision

IPF

idiopathic pulmonary fibrosis

IPF-CS

idiopathic pulmonary fibrosis clinical syndrome

LOS

length of stay

NHS

National Health Service

Gribbin J, Hubbard RB, Le Jeune I, Smith CJ, West J, Tata LJ. Incidence and mortality of idiopathic pulmonary fibrosis and sarcoidosis in the UK. Thorax. 2006;61(11):980-985. [CrossRef] [PubMed]
 
Johnston I, Britton J, Kinnear W, Logan R. Rising mortality from cryptogenic fibrosing alveolitis. BMJ. 1990;301(6759):1017-1021. [CrossRef] [PubMed]
 
Hubbard R, Johnston I, Coultas DB, Britton J. Mortality rates from cryptogenic fibrosing alveolitis in seven countries. Thorax. 1996;51(7):711-716. [CrossRef] [PubMed]
 
Raghu G, Weycker D, Edelsberg J, Bradford WZ, Oster G. Incidence and prevalence of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. 2006;174(7):810-816. [CrossRef] [PubMed]
 
Navaratnam V, Fleming KM, West J, et al. The rising incidence of idiopathic pulmonary fibrosis in the UK. Thorax. 2011;66(6):462-467. [CrossRef] [PubMed]
 
Hospital episode statistics. The Health and Social Care Information CentreHospital episode statistics. The Health and Social Care Information Centre website.http://www.hesonline.nhs.uk/Ease/servlet/ContentServer?siteID=1937&categoryID=214. Accessed October 3, 2011.
 
World Health OrganizationWorld Health Organization. International Statistical Classification of Diseases and Health Related Problems. 10th revision. Geneva, Switzerland: World Health Organization; 2004.
 
Raghu G, Collard HR, Egan JJ, et al;. ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med. 2011;183(6):788-824. [CrossRef] [PubMed]
 
Population estimates. Office for National Statistics websitePopulation estimates. Office for National Statistics website. http://www.ons.gov.uk/ons/taxonomy/index.html?nscl=Population+Estimates. Accessed October 3, 2011.
 
Publications. Department of Health website.http://www.dh.gov.uk/health/category/publications/. Accessed February 27, 2012.
 
Johnston ID, Bleasdale C, Hind CR, Woodcock AA. Accuracy of diagnostic coding of hospital admissions for cryptogenic fibrosing alveolitis. Thorax. 1991;46(8):589-591. [CrossRef] [PubMed]
 
 Improving Data Quality in the NHS Annual Report on the PbR Assurance Programme. Comorbidity Measures for Use With Administrative Data. London, England: Audit CommissionHealth; 2010:1-36.
 
Fell CD, Martinez FJ, Liu LX, et al. Am J Respir Crit Care Med.. 2010;181(8):832-837. [CrossRef] [PubMed]
 
Collard HR, Ward AJ, Lanes S, Cortney Hayflinger D, Rosenberg DM, Hunsche E. Burden of illness in idiopathic pulmonary fibrosis. J Med Econ.. 2012;15(5):829-835. [CrossRef] [PubMed]
 
Gribbin J, Hubbard R, Smith C. Role of diabetes mellitus and gastro-oesophageal reflux in the aetiology of idiopathic pulmonary fibrosis. Respir Med. 2009;103(6):927-931. [CrossRef] [PubMed]
 
Le Jeune I, Gribbin J, West J, Smith C, Cullinan P, Hubbard R. The incidence of cancer in patients with idiopathic pulmonary fibrosis and sarcoidosis in the UK. Respir Med. 2007;101(12):2534-2540. [CrossRef] [PubMed]
 
Fioret D, Mannino D, Roman J. In-hospital mortality and costs related to idiopathic pulmonary fibrosis between 1993 and 2008. Chest.. 2011;140(4):1038A. [CrossRef]
 
Mannino DM, Etzel RA, Parrish RG. Pulmonary fibrosis deaths in the United States, 1979-1991. An analysis of multiple-cause mortality data. Am J Respir Crit Care Med. 1996;153(5):1548-1552. [PubMed]
 
Olson AL, Swigris JJ, Lezotte DC, Norris JM, Wilson CG, Brown KK. Mortality from pulmonary fibrosis increased in the United States from 1992 to 2003. Am J Respir Crit Care Med. 2007;176(3):277-284. [CrossRef] [PubMed]
 
HCUPnet. Agency for Healthcare Research and Quality/US Department of Health & Human Services websiteHCUPnet. Agency for Healthcare Research and Quality/US Department of Health & Human Services website. http://hcupnet.ahrq.gov. Accessed March 4, 2012.
 
Stern JB, Mal H, Groussard O, et al. Prognosis of patients with advanced idiopathic pulmonary fibrosis requiring mechanical ventilation for acute respiratory failure. Chest. 2001;120(1):213-219. [CrossRef] [PubMed]
 
Blivet S, Philit F, Sab JM, et al. Outcome of patients with idiopathic pulmonary fibrosis admitted to the ICU for respiratory failure. Chest. 2001;120(1):209-212. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1. Estimated number of admissions from idiopathic pulmonary fibrosis clinical syndrome, age standardized to the 2010 population of England. ICD-10 = International Classification of Diseases and Related Health Problems, 10th Revision.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 —Crude Admission Rates and Poisson Regression Modeling of Hospital Admissions for IPF-CS

ICD-10 = International Classification of Diseases and Related Health Problems, 10th Revision; IPF-CS = idiopathic pulmonary fibrosis clinical syndrome.

a 

Admission-rate ratios are adjusted for age groups.

b 

P for trend < .0001.

Table Graphic Jump Location
Table 2 —Crude Admission Rates and Poisson Regression Modeling of Admissions of IPF-CS Stratified by Sex

See Table 1 legend for expansion of abbreviations.

a 

Admission rate ratios are adjusted for calendar period.

b 

Likelihood ratio test, P < .0001.

c 

Likelihood ratio test, P < .016.

Table Graphic Jump Location
Table 3 —Bed Days, Mean Length of Stay, and Mean Age at Time of Admission for Individuals With IPF-CS

See Table 1 legend for expansion of abbreviations.

a 

Linear regression, P < .0001.

Table Graphic Jump Location
Table 4 —Total Number of Bed Days and Associated Cost for IPF-CS

NHS = National Health Service. See Table 1 for expansion of other abbreviation.

a 

Linear regression, P = .004.

References

Gribbin J, Hubbard RB, Le Jeune I, Smith CJ, West J, Tata LJ. Incidence and mortality of idiopathic pulmonary fibrosis and sarcoidosis in the UK. Thorax. 2006;61(11):980-985. [CrossRef] [PubMed]
 
Johnston I, Britton J, Kinnear W, Logan R. Rising mortality from cryptogenic fibrosing alveolitis. BMJ. 1990;301(6759):1017-1021. [CrossRef] [PubMed]
 
Hubbard R, Johnston I, Coultas DB, Britton J. Mortality rates from cryptogenic fibrosing alveolitis in seven countries. Thorax. 1996;51(7):711-716. [CrossRef] [PubMed]
 
Raghu G, Weycker D, Edelsberg J, Bradford WZ, Oster G. Incidence and prevalence of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. 2006;174(7):810-816. [CrossRef] [PubMed]
 
Navaratnam V, Fleming KM, West J, et al. The rising incidence of idiopathic pulmonary fibrosis in the UK. Thorax. 2011;66(6):462-467. [CrossRef] [PubMed]
 
Hospital episode statistics. The Health and Social Care Information CentreHospital episode statistics. The Health and Social Care Information Centre website.http://www.hesonline.nhs.uk/Ease/servlet/ContentServer?siteID=1937&categoryID=214. Accessed October 3, 2011.
 
World Health OrganizationWorld Health Organization. International Statistical Classification of Diseases and Health Related Problems. 10th revision. Geneva, Switzerland: World Health Organization; 2004.
 
Raghu G, Collard HR, Egan JJ, et al;. ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med. 2011;183(6):788-824. [CrossRef] [PubMed]
 
Population estimates. Office for National Statistics websitePopulation estimates. Office for National Statistics website. http://www.ons.gov.uk/ons/taxonomy/index.html?nscl=Population+Estimates. Accessed October 3, 2011.
 
Publications. Department of Health website.http://www.dh.gov.uk/health/category/publications/. Accessed February 27, 2012.
 
Johnston ID, Bleasdale C, Hind CR, Woodcock AA. Accuracy of diagnostic coding of hospital admissions for cryptogenic fibrosing alveolitis. Thorax. 1991;46(8):589-591. [CrossRef] [PubMed]
 
 Improving Data Quality in the NHS Annual Report on the PbR Assurance Programme. Comorbidity Measures for Use With Administrative Data. London, England: Audit CommissionHealth; 2010:1-36.
 
Fell CD, Martinez FJ, Liu LX, et al. Am J Respir Crit Care Med.. 2010;181(8):832-837. [CrossRef] [PubMed]
 
Collard HR, Ward AJ, Lanes S, Cortney Hayflinger D, Rosenberg DM, Hunsche E. Burden of illness in idiopathic pulmonary fibrosis. J Med Econ.. 2012;15(5):829-835. [CrossRef] [PubMed]
 
Gribbin J, Hubbard R, Smith C. Role of diabetes mellitus and gastro-oesophageal reflux in the aetiology of idiopathic pulmonary fibrosis. Respir Med. 2009;103(6):927-931. [CrossRef] [PubMed]
 
Le Jeune I, Gribbin J, West J, Smith C, Cullinan P, Hubbard R. The incidence of cancer in patients with idiopathic pulmonary fibrosis and sarcoidosis in the UK. Respir Med. 2007;101(12):2534-2540. [CrossRef] [PubMed]
 
Fioret D, Mannino D, Roman J. In-hospital mortality and costs related to idiopathic pulmonary fibrosis between 1993 and 2008. Chest.. 2011;140(4):1038A. [CrossRef]
 
Mannino DM, Etzel RA, Parrish RG. Pulmonary fibrosis deaths in the United States, 1979-1991. An analysis of multiple-cause mortality data. Am J Respir Crit Care Med. 1996;153(5):1548-1552. [PubMed]
 
Olson AL, Swigris JJ, Lezotte DC, Norris JM, Wilson CG, Brown KK. Mortality from pulmonary fibrosis increased in the United States from 1992 to 2003. Am J Respir Crit Care Med. 2007;176(3):277-284. [CrossRef] [PubMed]
 
HCUPnet. Agency for Healthcare Research and Quality/US Department of Health & Human Services websiteHCUPnet. Agency for Healthcare Research and Quality/US Department of Health & Human Services website. http://hcupnet.ahrq.gov. Accessed March 4, 2012.
 
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  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543