Evaluating the predictive value of osteoarthritis diagnoses in an administrative database

Association of chronic pain with comorbidities and health care utilization: a retrospective cohort study using health administrative data

ABSTRACT

Health administrative data provide a potentially robust information source regarding the substantial burden chronic pain exerts on individuals and the health care system. This study aimed to use health administrative data to estimate comorbidity prevalence and annual health care utilization associated with chronic pain in Newfoundland and Labrador, Canada. Applying the validated Chronic Pain Algorithm to provincial Fee-for-Service Physician Claims File data (1999-2009) established the Chronic Pain (n = 184,580) and No Chronic Pain (n = 320,113) comparator groups. Applying the Canadian Chronic Disease Surveillance System coding algorithms to Claims File and Provincial Discharge Abstract Data (1999-2009) determined the prevalence of 16 comorbidities. The 2009/2010 risk and person-year rate of physician and diagnostic imaging visits and hospital admissions were calculated and adjusted using the robust Poisson model with log link function (risks) and negative binomial model (rates). Results indicated a significantly higher prevalence of all comorbidities and up to 4 times the odds of multimorbidity in the Chronic Pain Group (P-value < 0.001). Chronic Pain Group members accounted for 58.8% of all physician visits, 57.6% of all diagnostic imaging visits, and 54.2% of all hospital admissions in 2009/2010, but only 12% to 16% of these were for pain-related conditions as per recorded diagnostic codes. The Chronic Pain Group had significantly higher rates of physician visits and high-cost hospital admission/diagnostic imaging visits (P-value < 0.001) when adjusted for demographics and comorbidities. Observations made using this methodology supported that people identified as having chronic pain have higher prevalence of comorbidities and use significantly more publicly funded health services.

Risks of solid cancers in elderly persons with osteoarthritis or ankylosing spondylitis

OBJECTIVES

Patients with osteoarthritis and ankylosing spondylitis have lower cancer-related mortality than the general population. We examined risks of solid cancers at 16 sites in elderly patients with knee or hip osteoarthritis (KHOA) or ankylosing spondylitis.

METHODS

In this population-based retrospective cohort study, we used US Medicare data from 1999 to 2010 to identify cohorts of persons with KHOA or ankylosing spondylitis, and a general population group without either condition, who were followed through 2015. We compared cancer incidence among groups, adjusted for age, sex, race, socioeconomic characteristics, geographic region, smoking and comorbidities.

RESULTS

We studied 2 701 782 beneficiaries with KHOA, 13 044 beneficiaries with ankylosing spondylitis, and 10 859 304 beneficiaries in the general population group. Beneficiaries with KHOA had lower risks of cancer of the oropharynx, oesophagus, stomach, colon/rectum, hepatobiliary tract, pancreas, larynx, lung, and ovary than the general population. However, beneficiaries with KHOA had higher risks of melanoma, renal cell cancer, and cancer of the bladder, breast, uterus and prostate. Associations were similar in ankylosing spondylitis, with lower risks of cancer of the oesophagus, stomach, and lung, and higher risks of melanoma, renal cell cancer, and cancer of the renal pelvis/ureter, bladder, breast, and prostate.

CONCLUSION

Lower risks of highly prevalent cancers, including colorectal and lung cancer, may explain lower cancer-related mortality in patients with KHOA or ankylosing spondylitis. Similarities in cancer risks between KHOA and AS implicate a common risk factor, possibly chronic NSAID use.

Influence of opioid prescribing standards on health outcomes among patients with long-term opioid use: a longitudinal cohort study

Background:

The College of Physicians and Surgeons of British Columbia introduced opioid prescribing standards and guidelines in mid-2016 in British Columbia. We evaluated impacts of the standards and guidelines on health outcomes.

Methods:

We conducted a longitudinal study with repeated measures using administrative data from December 2013 to March 2017. The study included BC patients with long-term use of prescription opioids. Those with a history of long-term care, palliative care or cancer were excluded. Patients were followed for a 12-month prepolicy period and 10-month postpolicy period and compared with historical controls. We estimated changes in level (sudden changes) and monthly trend (gradual changes) of rates of opioid overdose hospital admission, and secondary outcomes of all-cause hospital admission, all-cause emergency department visits, opioid overdose mortality and all-cause mortality.

Results:

The study included 68 113 patients in the main cohort and 68 429 historical controls. We did not find significant changes to opioid overdose hospital admissions in level (adjusted rate ratio [RR] 0.83, 95% confidence interval [CI] 0.45–1.54) or in trend (adjusted RR 1.00, 95% CI 0.91–1.10). All-cause hospital admissions declined in level but may have increased in trend, suggesting that a temporary decrease in hospital admissions may have occurred. We found no significant changes in all-cause emergency department visits, opioid overdose mortality or all-cause mortality.

Interpretation:

Among patients with a history of long-term prescription opioid use, the regulatory prescribing standards and guidelines were not associated with changes in opioid overdose hospital admissions, all-cause emergency department visits, opioid overdose mortality or all-cause mortality, or with a sustained reduction in all-cause hospital admissions, over a 10-month period after they were introduced. Future research should investigate whether opioid prescribing standards or guidelines are associated with use of nonopioid analgesic medications or nonpharmacologic treatments.

Identifying cases of chronic pain using health administrative data: A validation study

Background

Most prevalence estimates of chronic pain are derived from surveys and vary widely, both globally (2%–54%) and in Canada (6.5%–44%). Health administrative data are increasingly used for chronic disease surveillance, but their validity as a source to ascertain chronic pain cases is understudied.

Aim

The aim of this study was to derive and validate an algorithm to identify cases of chronic pain as a single chronic disease using provincial health administrative data.

Methods

A reference standard was developed and applied to the electronic medical records data of a Newfoundland and Labrador general population sample participating in the Canadian Primary Care Sentinel Surveillance Network. Chronic pain algorithms were created from the administrative data of patient populations with chronic pain, and their classification performance was compared to that of the reference standard via statistical tests of selection accuracy.

Results

The most performant algorithm for chronic pain case ascertainment from the Medical Care Plan Fee-for-Service Physicians Claims File was one anesthesiology encounter ever recording a chronic pain clinic procedure code OR five physician encounter dates recording any pain-related diagnostic code in 5 years with more than 183 days separating at least two encounters. The algorithm demonstrated 0.703 (95% confidence interval [CI], 0.685–0.722) sensitivity, 0.668 (95% CI, 0.657–0.678) specificity, and 0.408 (95% CI, 0.393–0.423) positive predictive value. The chronic pain algorithm selected 37.6% of a Newfoundland and Labrador provincial cohort.

Conclusions

A health administrative data algorithm was derived and validated to identify chronic pain cases and estimate disease burden in residents attending fee-for-service physician encounters in Newfoundland and Labrador.

Identifying monoclonal gammopathy of undetermined significance in electronic health data

PURPOSE

Monoclonal gammopathy of undetermined significance (MGUS) is a prevalent yet largely asymptomatic precursor to multiple myeloma. Patients with MGUS must undergo regular surveillance and testing, with few known predictors of progression. We developed an algorithm to identify MGUS patients in electronic health data to facilitate large-scale, population-based studies of this premalignant condition.

METHODS

We developed a four-step algorithm using electronic health record and health claims data from men and women aged 50 years or older receiving care from a large, multispecialty medical group between 2007 and 2015. The case definition required patients to have at least two MGUS ICD-9 diagnosis codes within 12 months, at least one serum and/or urine protein electrophoresis and one immunofixation test, and at least one in-office hematology/oncology visit. Medical charts for selected cases were abstracted then adjudicated independently by two physicians. We assessed algorithm validity by positive predictive value (PPV).

RESULTS

We identified 833 people with at least two MGUS diagnosis codes; 429 (52%) met all four algorithm criteria. We randomly selected 252 charts for review, including 206 from patients meeting all four algorithm criteria. The PPV for the 206 algorithm-identified charts was 76% (95% CI, 70%-82%). Among the 49 cases deemed to be false positives (24%), 33 were judged to have multiple myeloma or another lymphoproliferative condition, such as lymphoma.

CONCLUSIONS

We developed a simple algorithm that identified MGUS cases in electronic health data with reasonable accuracy. Inclusion of additional steps to eliminate cases with malignant disease may improve algorithm performance.

Influence of opioid prescribing standards on drug use among patients with long-term opioid use: a longitudinal cohort study

BACKGROUND

In mid-2016, the College of Physicians and Surgeons of British Columbia (CPSBC) issued prescribing standards and guidelines relating to opioid drugs. We evaluated the impact of these regulatory standards and guidelines on prescription drug use among patients in the province with long-term opioid use.

METHODS

We conducted a cohort study with monthly repeated measures using administrative health data in British Columbia. Patients with long-term prescription opioid use were followed for a 12-month prepolicy period and 10-month postpolicy period, and were compared with a historical control cohort. We excluded patients with a history of long-term care, palliative care or cancer. We estimated changes in use of opioids, high-dose opioids (> 90 mg of morphine equivalents/d), opioids with sedatives/hypnotics, and opioid discontinuation.

RESULTS

The study population included 68 113 patients in the policy cohort and 68 429 patients in the historical control cohort. Following the introduction of the standards and guidelines, the average monthly use of opioids declined (adjusted difference -57 mg of morphine equivalents, 95% confidence interval [CI] -74 to -39) and discontinuation of opioids increased (odds ratio [OR] 1.24, 95% CI 1.16 to 1.32). Among patients prescribed high-dose opioids, switching to lower-dose opioids increased (OR 1.88, 95% CI 1.63 to 2.17), but discontinuation did not change significantly (OR 1.21, 95% CI 0.91 to 1.59).

INTERPRETATION

The CPSBC's regulatory standards and guidelines were associated with modestly reduced opioid use and increased switching from high-dose to lower-dose opioids among patients with long-term use of prescribed opioids. Assessment of the potential impacts on health outcomes will be necessary for understanding the implications of the standards and guidelines.

Validation of algorithms to identify knee osteoarthritis patients in the claims database

BACKGROUND

To identify knee osteoarthritis (OA) patients among OA patients in the claims database.

METHODS

All patients with OA diagnostic codes for any sites (M15 to M19) in 2014 were recruited from a single academic referral hospital. After excluding patients who had inflammatory arthritis or were less than 50 years of age, we identified data for the overall OA population. Radiographic knee OA of Kellgren and Lawrence grades ≥2 is considered the gold standard for knee OA, and we evaluated the sensitivity, specificity, and positive predictive value (PPV) of three operational definitions using the diagnostic codes in the claims database. The operational definitions were: (1) gonarthrosis (M17); (2) any site of OA (M15 to M19) with knee X-ray; and (3) (1) or (2).

RESULTS

A total of 7959 OA patients were included in this study of whom 74.5% were women. The PPV of gonarthrosis (M17) was 0.67 (95% CI 0.65-0.69), and sensitivity was 0.44 (95% CI 0.42-0.46). The PPV and sensitivity of any OA site (M15 to M19) with knee X-ray were 0.65 (95% CI 0.62-0.67), and 0.37 (95% CI 0.35-0.39), respectively. When knee OA was defined as satisfying either of the two above definitions, PPV was 0.63 (95% CI 0.62-0.65) and sensitivity 0.55 (95% CI 0.53-0.57).

CONCLUSIONS

Knee OA patients can be identified in a claims database using the algorithms of gonarthrosis (M17) or any site of OA (M15 to M19) with a performed knee X-ray.

Prevalence and treatment of hip and knee osteoarthritis in people aged 60 years or older in Germany: an analysis based on health insurance claims data

Objective

Osteoarthritis (OA) is highly prevalent throughout the world, especially in the elderly population, and is strongly associated with patients’ frailty. However, little is known about the prevalence and treatment of OA in elderly patients in routine clinical care in Germany.

Materials and methods

As a part of Linking Patient-Reported Outcomes with CLAIms Data for Health Services Research in Rheumatology (PROCLAIR), a cross-sectional study using claims data from a large Germany statutory health insurance (BARMER) was conducted. We included people aged 60 years or older and assessed the prevalence of OA of the hip or knee, defined as having outpatient diagnoses (ICD: M16 or M17) in at least two quarters of 2014. The use of conservative treatment, including analgesics and physical therapy, and total joint replacement was studied. Analyses were stratified by age, sex, comorbidities, and level of care dependency defined by social law.

Results

A total of 595,754 patients (mean age: 74.9 years; 69.8% female) were diagnosed with OA (21.8%), with the highest prevalence in those between 80 and 89 years (31.0%) and in females compared to males (23.9% vs 18.3%). Prevalence decreased with increasing level of care dependency from 30.5% in patients with a low level (0/1) to 18.7% in the highest level of care dependency. A total of 63.4% of the patients with OA received analgesics, with higher use with increasing age. Physical therapy was prescribed to 43.1% of the patients, but use decreased with age. In all, 5.3% of the patients received total joint replacement in 2014.

Conclusion

The lower frequency of coded OA with increasing level of care dependency may reflect underdiagnosis, and patients with many other medical problems seem to be at risk for inadequate recognition and treatment of their OA.

The Canadian Chronic Disease Surveillance System: A model for collaborative surveillance

Chronic diseases have a major impact on populations and healthcare systems worldwide. Administrative health data are an ideal resource for chronic disease surveillance because they are population-based and routinely collected. For multi-jurisdictional surveillance, a distributed model is advantageous because it does not require individual-level data to be shared across jurisdictional boundaries. Our objective is to describe the process, structure, benefits, and challenges of a distributed model for chronic disease surveillance across all Canadian provinces and territories (P/Ts) using linked administrative data. The Public Health Agency of Canada (PHAC) established the Canadian Chronic Disease Surveillance System (CCDSS) in 2009 to facilitate standardized, national estimates of chronic disease prevalence, incidence, and outcomes. The CCDSS primarily relies on linked health insurance registration files, physician billing claims, and hospital discharge abstracts. Standardized case definitions and common analytic protocols are applied to the data for each P/T; aggregate data are shared with PHAC and summarized for reports and open access data initiatives. Advantages of this distributed model include: it uses the rich data resources available in all P/Ts; it supports chronic disease surveillance capacity building in all P/Ts; and changes in surveillance methodology can be easily developed by PHAC and implemented by the P/Ts. However, there are challenges: heterogeneity in administrative databases across jurisdictions and changes in data quality over time threaten the production of standardized disease estimates; a limited set of databases are common to all P/Ts, which hinders potential CCDSS expansion; and there is a need to balance comprehensive reporting with P/T disclosure requirements to protect privacy. The CCDSS distributed model for chronic disease surveillance has been successfully implemented and sustained by PHAC and its P/T partners. Many lessons have been learned about national surveillance involving jurisdictions that are heterogeneous with respect to healthcare databases, expertise and analytical capacity, population characteristics, and priorities.

Alternative Methods for Defining Osteoarthritis and the Impact on Estimating Prevalence in a US Population-Based Survey

OBJECTIVE

Provide a contemporary estimate of osteoarthritis (OA) by comparing the accuracy and prevalence of alternative definitions of OA.

METHODS

The Medical Expenditure Panel Survey (MEPS) household component (HC) records respondent-reported medical conditions as open-ended responses; professional coders translate these responses into International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for the medical conditions files. Using these codes and other data from the MEPS-HC medical conditions files, we constructed 3 case definitions of OA and assessed them against medical provider diagnoses of ICD-9-CM 715 (osteoarthrosis and allied disorders) in a MEPS subsample. The 3 definitions were 1) strict = ICD-9-CM 715; 2) expanded = ICD-9-CM 715, 716 (other and unspecified arthropathies) OR 719 (other and unspecified disorders of joint); and 3) probable = strict OR expanded + respondent-reported prior diagnosis of OA or other arthritis excluding rheumatoid arthritis.

RESULTS

Sensitivity and specificity of the 3 definitions, respectively, were 34.6% and 97.5% for strict, 73.8% and 90.5% for expanded, and 62.9% and 93.5% for probable.

CONCLUSION

The strict definition for OA (ICD-9-CM 715) excludes many individuals with OA. The probable definition of OA has the optimal combination of sensitivity and specificity relative to the 2 other MEPS-based definitions and yields a national annual estimate of 30.8 million adults with OA (13.4% of US adult population) for 2008-2011.

The Implications of Inaccuracy: Comparison of Coding in Heterotopic Ossification and Associated Trauma

Retrospective studies using large databases serve a major purpose in providing evidence in the current literature. However, the quality of medical coding is highly variable. This retrospective cohort study aimed to evaluate the documentation regarding the diagnosis of heterotopic ossification (HO) and the implications it may have for conducting retrospective research using electronic medical records (EMRs). A retrospective chart review using the EMR was performed to identify all patients with a diagnosis of HO within 7 university-affiliated hospital facilities. A limited data set request was conducted for all patients with HO-specific International Classification of Diseases, Ninth Revision (ICD-9) codes and additional nonspecific musculoskeletal codes to capture patients with HO who were improperly coded. A total of 522 patients were identified-26 patients with specific HO codes and 496 patients with nonspecific codes. Imaging and clinical notes were inspected for evidence and location of HO, and histories were reviewed for traumatic injury mechanism. Two-thirds of the patients with HO were discovered by reviewing miscellaneous musculoskeletal ICD-9 codes. Thirty-eight percent of the patients with an HO-specific ICD-9 code had no evidence of HO in their EMR. Thirty-three patients had a clinical history of a traumatic injury preceding HO formation, but only 16 of the 33 had documented ICD-9 codes for the injury. The utility of databases in retrospective research is dependent on the integrity of the coding. This study questions the use of retrospective reviews for patients with uncommon diagnoses and shows how painstaking verification may be necessary to ensure that research conclusions are based on accurate data. [Orthopedics. 2017; 40(4):237-241.].

Validation of Administrative Osteoarthritis Diagnosis Using a Clinical and Radiological Population-Based Cohort

Objectives. The validity of administrative osteoarthritis (OA) diagnosis in British Columbia, Canada, was examined against X-rays, magnetic resonance imaging (MRI), self-report, and the American College of Rheumatology criteria. Methods. During 2002–2005, 171 randomly selected subjects with knee pain aged 40–79 years underwent clinical assessment for OA in the knee, hip, and hands. Their administrative health records were linked during 1991–2004, in which OA was defined in two ways: (AOA1) at least one physician's diagnosis or hospital admission and (AOA2) at least two physician's diagnoses in two years or one hospital admission. Sensitivity, specificity, and predictive values were compared using four reference standards. Results. The mean age was 59 years and 51% were men. The proportion of OA varied from 56.3 to 89.7% among men and 77.4 to 96.4% among women according to reference standards. Sensitivity and specificity varied from 21 to 57% and 75 to 100%, respectively, and PPVs varied from 82 to 100%. For MRI assessment, the PPV of AOA2 was 100%. Higher sensitivity was observed in AOA1 than AOA2 and the reverse was true for specificity and PPV. Conclusions. The validity of administrative OA in British Columbia varied due to case definitions and reference standards. AOA2 is more suitable for identifying OA cases for research using this Canadian database.

Effect of Comorbid Knee and Hip Osteoarthritis on Longitudinal Clinical and Health Care Use Outcomes in Older Adults With New Visits for Back Pain

OBJECTIVE

To examine if a comorbid diagnosis of knee or hip osteoarthritis (OA) in older adults with new back pain visits is associated with long-term patient-reported outcomes and back-related health care use.

DESIGN

Prospective cohort study.

SETTING

Three integrated health systems forming the Back pain Outcomes using Longitudinal Data cohort.

PARTICIPANTS

Participants (N=5155) were older adults (≥65y) with a new visit for back pain and a complete electronic health record data.

INTERVENTIONS

Not applicable; we obtained OA diagnoses using diagnostic codes in the electronic health record 12 months prior to the new back pain visit.

MAIN OUTCOME MEASURES

The Roland-Morris Disability Questionnaire (RDQ) and the EuroQol-5D (EQ-5D) were key patient-reported outcomes. Health care use, measured by relative-value units (RVUs), was summed for the 12 months after the initial visit. We used linear mixed-effects models to model patient-reported outcomes. We also used generalized linear models to test the association between comorbid knee or hip OA and total back-related RVUs.

RESULTS

Of the 5155 participants, 368 (7.1%) had a comorbid knee OA diagnosis, and 94 (1.8%) had a hip OA diagnosis. Of the participants, 4711 (91.4%) had neither knee nor hip OA. In adjusted models, the 12-month RDQ score was 1.23 points higher (95% confidence interval [CI], 0.72-1.74) for patients with knee OA and 1.26 points higher (95% CI, 0.24-2.27) for those with hip OA than those without knee or hip OA, respectively. A lower EQ-5D score was found among participants with knee OA (.02 lower; 95% CI, -.04 to -.01) and hip OA diagnoses (.03 lower; 95% CI, -.05 to -.01) compared with those without knee or hip OA, respectively. Comorbid knee or hip OA was not significantly associated with total 12-month back-related resource use.

CONCLUSIONS

Comorbid knee or hip OA in older adults with a new back pain visit was associated with modestly worse long-term disability and health-related quality of life.

Diagnostic accuracy of administrative data algorithms in the diagnosis of osteoarthritis: a systematic review

Background

Administrative health care data are frequently used to study disease burden and treatment outcomes in many conditions including osteoarthritis (OA). OA is a chronic condition with significant disease burden affecting over 27 million adults in the US. There are few studies examining the performance of administrative data algorithms to diagnose OA. The purpose of this study is to perform a systematic review of administrative data algorithms for OA diagnosis; and, to evaluate the diagnostic characteristics of algorithms based on restrictiveness and reference standards.

Methods

Two reviewers independently screened English-language articles published in Medline, Embase, PubMed, and Cochrane databases that used administrative data to identify OA cases. Each algorithm was classified as restrictive or less restrictive based on number and type of administrative codes required to satisfy the case definition. We recorded sensitivity and specificity of algorithms and calculated positive likelihood ratio (LR+) and positive predictive value (PPV) based on assumed OA prevalence of 0.1, 0.25, and 0.50.

Results

The search identified 7 studies that used 13 algorithms. Of these 13 algorithms, 5 were classified as restrictive and 8 as less restrictive. Restrictive algorithms had lower median sensitivity and higher median specificity compared to less restrictive algorithms when reference standards were self-report and American college of Rheumatology (ACR) criteria. The algorithms compared to reference standard of physician diagnosis had higher sensitivity and specificity than those compared to self-reported diagnosis or ACR criteria.

Conclusions

Restrictive algorithms are more specific for OA diagnosis and can be used to identify cases when false positives have higher costs e.g. interventional studies. Less restrictive algorithms are more sensitive and suited for studies that attempt to identify all cases e.g. screening programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12911-016-0319-y) contains supplementary material, which is available to authorized users.

The rate of joint replacement in osteoarthritis depends on the patient's socioeconomic status

Background and purpose - Assessment of potential disparities in access to care is a vital part of achieving equity in health and healthcare. We have therefore studied the effect of socioeconomic status (SES) on the rates of knee and hip replacement due to osteoarthritis. Methods - This was a cohort study in Skåne, Sweden. We included all residents aged ≥ 35 years with consultations between 2004 and 2013 for hip or knee osteoarthritis. We retrieved individual information on income, education, and occupation and evaluated the rates of knee and hip replacement according to SES, with adjustment for age and sex. Professionals, legislators, senior officials, and managers, and individuals with the longest education, served as the reference group. Results - We followed 50,498 knee osteoarthritis patients (59% women) and 20,882 hip osteoarthritis patients (58% women). The mutually adjusted rate of knee replacement was lower in those with an elementary occupation (hazard ratio (HR) = 0.81, 95% CI: 0.72-0.92), in craft workers and those with related trades (HR = 0.88, CI: 0.79-0.98), and in skilled agricultural/fishery workers (HR = 0.83, CI: 0.72-0.96), but higher in the 2 least educated groups (HR = 1.2 in both). The rate of hip replacement was lower in those with an elementary occupation (HR = 0.77, 95% CI: 0.68-0.87), in plant and machine operators/assemblers (HR = 0.83, CI: 0.75-0.93), and service workers/shop assistants (HR = 0.88, CI: 0.80-0.96). The rate of hip replacement was higher in the highest income group (HR = 1.1, 95% CI: 1.0-1.2). Interpretation - There was a lower rate of joint replacement in osteoarthritis patients working in professions often associated with lower socioeconomic status, suggesting inequity in access to care. However, the results are not unanimous, as the rate of knee replacement was higher in the least educated groups.

The use of administrative health care databases to identify patients with rheumatoid arthritis

OBJECTIVE

To validate and compare the decision rules to identify rheumatoid arthritis (RA) in administrative databases.

METHODS

A study was performed using administrative health care data from a population of 1 million people who had access to universal health care. Information was available on hospital discharge abstracts and physician billings. RA cases in health administrative databases were matched 1:4 by age and sex to randomly selected controls without inflammatory arthritis. Seven case definitions were applied to identify RA cases in the health administrative data, and their performance was compared with the diagnosis by a rheumatologist. The validation study was conducted on a sample of individuals with administrative data who received a rheumatologist consultation at the Arthritis Center of Nova Scotia.

RESULTS

We identified 535 RA cases and 2,140 non-RA, noninflammatory arthritis controls. Using the rheumatologist's diagnosis as the gold standard, the overall accuracy of the case definitions for RA cases varied between 68.9% and 82.9% with a kappa statistic between 0.26 and 0.53. The sensitivity and specificity varied from 20.7% to 94.8% and 62.5% to 98.5%, respectively. In a reference population of 1 million, the estimated annual number of incident cases of RA was between 176 and 1,610 and the annual number of prevalent cases was between 1,384 and 5,722.

CONCLUSION

The accuracy of case definitions for the identification of RA cases from rheumatology clinics using administrative health care databases is variable when compared to a rheumatologist's assessment. This should be considered when comparing results across studies. This variability may also be used as an advantage in different study designs, depending on the relative importance of sensitivity and specificity for identifying the population of interest to the research question.

Validity of gout diagnosis in Swedish primary and secondary care - a validation study

Background

The diagnostic golden standard for gout is to detect monosodium urate (MSU) crystals in synovial fluid. While some gout classification criteria include this variable, most gout diagnoses are based on clinical features. This discrepancy between clinical practice and classification criteria can hinder gout epidemiological studies. Here, the objective was to validate gout diagnoses (International Classification of Diseases (ICD)-10 gout codes) in primary and secondary care relative to five classification criteria (Rome, New York, ARA, Mexico, and Netherlands). The frequency with which MSU crystal identification was used to establish gout diagnosis was also determined.

Methods

In total, 394 patients with ≥1 ICD-10 gout diagnosis between 2009 and 2013 were identified from the medical records of two primary care centers (n = 262) and one secondary care center (n = 132) in Gothenburg, Sweden. Medical records were assessed for all classification criteria.

Results

Primary care patients met criteria cutoffs more frequently when ≥2 gout diagnoses were made. Even then, few primary care patients met the Rome and New York cutoffs (19 % and 8 %, respectively). The ARA, Mexico, and Netherlands cutoffs were met more frequently by primary care patients with ≥2 gout diagnoses (54 %, 81 %, and 80 %, respectively). Mexico and Netherlands cutoffs were met more frequently by the rheumatology department patients (80 % and 71 %, respectively), even when patients with only 1 gout diagnosis were included. Analysis of MSU crystals served to establish gout diagnoses in only 27 % of rheumatology department and 2 % of primary care cases.

Conclusions

If a patient was deemed to have gout at ≥2 primary care center or ≥1 rheumatology-center visits according to an ICD-10 gout code, the positive predictive value of this variable in relation with the Mexico and Netherlands classification criteria was ≥80 % for both primary care and rheumatology care settings in Sweden. MSU crystal identification was rarely used to establish gout diagnosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0614-2) contains supplementary material, which is available to authorized users.

Current and future impact of osteoarthritis on health care: a population-based study with projections to year 2032

OBJECTIVE

To estimate the current and future (to year 2032) impact of osteoarthritis (OA) health care seeking.

METHOD

Population-based study with prospectively ascertained data from the Skåne Healthcare Register (SHR), Sweden, encompassing more than 15 million person-years of primary and specialist outpatient care and hospitalizations. We studied all Skåne region residents aged ≥45 by the end of 2012 (n = 531, 254) and determined the prevalence of doctor-diagnosed OA defined as the proportion of the prevalent population that had received a diagnosis of OA of the knee, hip, hand, or other locations except the spine between 1999 and 2012. We projected consultation prevalence of OA until year 2032 using Statistics Sweden's (SCB) projected age and sex structure and prevalence of overweight and obesity.

RESULTS

In 2012 the proportion of population aged ≥45 with any doctor-diagnosed OA was 26.6% (95% confidence interval (CI): 26.5-26.8) (men 22.4%, women 30.5%). The most common locations were knee (13.8%), hip (5.8%) and hand (3.1%). Of the prevalent cases 26.8% had OA in multiple joints. By the year 2032, the proportion of the population aged ≥45 with doctor-diagnosed OA is estimated to increase from 26.6% to 29.5% (any location), from 13.8% to 15.7% for the knee and 5.8-6.9% for the hip.

CONCLUSION

In 2032, at least an additional 26,000 individuals per 1 million population aged ≥45 years are estimated to have consulted a physician for OA in a peripheral joint compared to 2012. These findings underscore the need to address modifiable risk factors and develop new effective OA treatments.

Risk of cardiovascular disease in patients with osteoarthritis: a prospective longitudinal study

OBJECTIVE

To determine the risk of cardiovascular disease (CVD) among osteoarthritis (OA) patients using population-based administrative data from British Columbia, Canada.

METHODS

The medical history of a random sample of 600,000 individuals from 1991-2009 was analyzed. A total of 12,745 OA cases and up to 3 non-OA individuals matched by age, sex, and year of diagnosis were followed for CVD events. Cox proportional hazards and Poisson regression models were used to estimate the relative risks (RRs) of CVD, myocardial infarction, ischemic heart disease (IHD), congestive heart failure (CHF), and stroke after adjusting for available sociodemographic and medical factors.

RESULTS

OA was an independent predictor of CVD. The adjusted RRs were 1.15 (95% confidence interval [95% CI] 1.04-1.27), 1.26 (95% CI 1.13-1.42), and 1.17 (95% CI 1.07-1.26) among older men, younger women, and older women, respectively. Analyses were stratified by age and sex due to statistically significant interactions between OA and age and sex. RRs among older men, younger women, and older women were 1.33 (95% CI 1.11-1.62), 1.66 (95% CI 1.37-2.01), and 1.45 (95% CI 1.22-1.72) for IHD, respectively, and 1.25 (95% CI 1.02-1.54), 1.29 (95% CI 1.00-1.68), and 1.20 (95% CI 1.03-1.39) for CHF, respectively. Compared to non-OA individuals, OA cases who underwent total joint replacements had a 26% increased risk of CVD.

CONCLUSION

This prospective longitudinal study suggests that OA is associated with an increased risk of CVD. Older men and adult women with OA had a higher risk of CVD, particularly IHD and CHF. Further studies are needed to confirm these results and to elucidate the potential biologic mechanisms.

Longer Term Effects of Total Knee Arthroplasty From a National Longitudinal Study

Objective: This study used data for 1996-2010 from a U.S. longitudinal sample of elderly individuals from the Health and Retirement Study (HRS) merged with Medicare claims data to assess changes in several dimensions of physical functioning and general health up to 68 months following total knee arthroplasty (TKA) receipt. Method: Using propensity score matching, we assessed outcomes at follow-up for Medicare beneficiaries receiving TKA and a comparable group of beneficiaries with the same osteoarthritis diagnoses (controls). Results: Receipt of TKA was most often associated with improvements in physical functioning, especially in physical functioning measures most directly related to the knee. General health of TKA recipients only improved relative to controls on 1 of the 3 study general health measures. Discussion: Improvements in physical functioning of TKA recipients persisted in this longer term analysis of outcome in a nationally representative population study.

Trends in primary total hip arthroplasty in Spain from 2001 to 2008: evaluating changes in demographics, comorbidity, incidence rates, length of stay, costs and mortality

BACKGROUND

Hip arthroplasties is one of the most frequent surgical procedures in Spain and are conducted mainly in elderly subjects. We aim to analyze changes in incidence, co-morbidity profile, length of hospital stay (LOHS), costs and in-hospital mortality (IHM) of patients undergoing primary total hip arthroplasty (THA) over an 8-year study period in Spain.

METHODS

We selected all surgical admissions in individuals aged ≥ 40 years who had received a primary THA (ICD-9-CM procedure code 81.51) between 2001 and 2008 from the National Hospital Discharge Database. Age- and sex-specific incidence rates, LOHS, costs and IHM were estimated for each year. Co-morbidity was assessed using the Charlson comorbidity index.Multivariate analysis of time trends was conducted using Poisson regression. Logistic regression models were conducted to analyze IHM.

RESULTS

We identified a total of 161,791 discharges of patients having undergone THA from 2001 to 2008. Overall crude incidence had increased from 99 to 105 THA per 100.000 inhabitants from 2001 to 2008 (p < 0.001). In 2001, 81% of patients had a Charlson Index of 0, 18.4% of 1-2, and 0.6% > 2 and in 2008, the prevalence of 1-2 or >2 had increased to 20.4% and 1.1% respectively (p < 0.001). The mean LOHS was 13 days in 2001 and decreased to 10.45 days in 2008 (p < 0.001). During the period studied, the mean cost per patient increased from 6,634 to 9,474 Euros. Multivariate analysis shows that from 2001 to 2008 the incidence of THA hospitalizations has significantly increased for both sexes and only men showed a significant reduction in IHM after THA.

CONCLUSIONS

The current study provides clear and valid data indicating increased incidence of primary THA in Spain from 2001 to 2008 with concomitant reductions in LOHS, slight reduction IHM, but a significant increase in cost per patient. The health profile of the patient undergoing a THA seems to be worsening in Spain.

Effect of Sociodemographic Factors on Surgical Consultations and Hip or Knee Replacements Among Patients with Osteoarthritis in British Columbia, Canada

Objective.

To quantify the effect of demographic variables and socioeconomic status (SES) on surgical consultation and total joint arthroplasty (TJA) rates among patients with osteoarthritis (OA), using population-based administrative data.

Methods.

A cohort study was conducted in British Columbia using population data from 1991 to 2004. From April 1996 to March 1998, we documented 34,420 new patients with OA and these patients were followed to March 2004 for their first surgical consultation and TJA. Effects of age, sex, and SES were evaluated by Cox proportional hazards models after adjusting for comorbidities and pain medication used.

Results.

During a mean 5.5-year followup period, 7475 patients with OA had their first surgical consultations and 2814 patients received TJA within a 6-year mean followup period. Crude hazards ratio (HR) for men compared to women was 1.25 (95% CI 1.20–1.31) for surgical consultation and was 1.14 (95% CI 1.06–1.23) for TJA. The interaction between sex and SES was significant. Stratified analysis showed among men an HR of 1.42 (95% CI 1.27–1.58) and 1.52 (95% CI 1.26–1.83) for surgical consultations and TJA, respectively, for the highest SES compared with the lowest SES quintiles. Similarly significant results were observed among women.

Conclusion.

Differential access to the healthcare system exists among patients with OA. Women with OA were less likely than men to see an orthopedic surgeon as well as to obtain TJA. Patients with higher SES consulted orthopedic surgeons more frequently and received more TJA than those with the lowest SES.

Development of a population-based microsimulation model of osteoarthritis in Canada

OBJECTIVES

The purpose of the study was to develop a population-based simulation model of osteoarthritis (OA) in Canada that can be used to quantify the future health and economic burden of OA under a range of scenarios for changes in the OA risk factors and treatments. In this article we describe the overall structure of the model, sources of data, derivation of key input parameters for the epidemiological component of the model, and preliminary validation studies.

DESIGN

We used the Population Health Model (POHEM) platform to develop a stochastic continuous-time microsimulation model of physician-diagnosed OA. Incidence rates were calibrated to agree with administrative data for the province of British Columbia, Canada. The effect of obesity on OA incidence and the impact of OA on health-related quality of life (HRQL) were modeled using Canadian national surveys.

RESULTS

Incidence rates of OA in the model increase approximately linearly with age in both sexes between the ages of 50 and 80 and plateau in the very old. In those aged 50+, the rates are substantially higher in women. At baseline, the prevalence of OA is 11.5%, 13.6% in women and 9.3% in men. The OA hazard ratios for obesity are 2.0 in women and 1.7 in men. The effect of OA diagnosis on HRQL, as measured by the Health Utilities Index Mark 3 (HUI3), is to reduce it by 0.10 in women and 0.14 in men.

CONCLUSIONS

We describe the development of the first population-based microsimulation model of OA. Strengths of this model include the use of large population databases to derive the key parameters and the application of modern microsimulation technology. Limitations of the model reflect the limitations of administrative and survey data and gaps in the epidemiological and HRQL literature.

Gout in the elderly--a population health study

OBJECTIVE

To determine the incidence, healthcare utilization, and costs in older adults with gout.

METHODS

A 5-year retrospective case-control study of patients with incident gout and matched controls was performed. Study variables were derived from health administrative data and included patient demographics, International Classification of Diseases diagnostic codes, and healthcare cost information.

RESULTS

There were 4,071 cases and 16,281 controls, providing a 5-year incidence of gout of 4.4%. The mean (+/-SD) age (77+/-7.3 and 76+/-7.1 yrs) and the male:female ratio (1.0:1.04) were similar in both groups. Gout was diagnosed by family physicians (77%), nonrheumatology subspecialists (18%), general internists (4%), and rheumatologists (0.02%). Hospitalizations were significantly higher in cases (p<0.001) in the year of diagnosis. Patients with gout had an average of 28.1 physician visits per year compared to 20.6 for controls (p<0.0001). Drug utilization for the treatment (nonsteroidal antiinflammatory drugs, colchicine, corticosteroids) and prevention (allopurinol, probenecid, sulfinpyrazone) of gout was significantly higher (p<0.0001). The average healthcare cost differential was +$134 (Cdn) per month (p<0.001) and +$8,020 per case over 5 years. These costs were due to hospital utilization (64.4%), medications (23.1%), and physician visits (12.5%).

CONCLUSION

Gout is associated with a high disease burden in older men and women. The cost is primarily attributable to hospitalization, probably due to the comorbidities associated with gout. As the majority of cases are managed by nonrheumatologists, it is important that guidelines for the diagnosis and treatment of gout are disseminated to and met by all physician groups.

Identification of patients with arthritis and arthritis-related functional limitation using administrative data

OBJECTIVE

To develop algorithms on the basis of administrative data to identify patients with arthritis and arthritis-related functional limitation (AFL).

STUDY DESIGN AND SETTING

In this retrospective study, 361 enrollees of a health plan underwent a clinical examination to confirm arthritis and assessment of functional limitation on the basis of responses to the health assessment questionnaire. Administrative data were obtained on these subjects and included arthritis drugs dispensed, as well as outpatient and emergency department diagnoses and procedures (including radiographic studies, arthritis procedures, and laboratory tests). Composite risk scores for arthritis and AFL were created on the basis of the association of arthritis-related healthcare utilization with confirmed arthritis and AFL. Algorithms were then developed on the basis of the composite risk scores using logistic regression models.

RESULTS

The algorithm using the arthritis composite score to identify arthritis patients had an area under the ROC curve (AUC) of 0.74, sensitivity of 75 percent and specificity of 57 percent. Similarly, the algorithm using the AFL composite score to identify patients with AFL had an AUC of 0.73, sensitivity of 62 percent, and specificity of 75 percent.

CONCLUSION

The developed algorithms will enable health plans to screen their enrollees for persons with arthritis and AFL. This will facilitate enrollment of patients with arthritis and AFL in disease management programs and/or targeted interventions.

Trends in physician-diagnosed osteoarthritis incidence in an administrative database in British Columbia, Canada, 1996-1997 through 2003-2004

OBJECTIVE

Prevalence of osteoarthritis (OA) is expected to increase due to population aging. However, there is little information on the trends in the incidence of OA over time. The purpose of this study was to describe changes in physician-diagnosed OA incidence rates between 1996-1997 and 2003-2004 in British Columbia (BC), Canada.

METHODS

We used data on all visits to health professionals and hospital admissions covered by the Medical Services Plan of BC (population approximately 4 million) for the fiscal years 1991-1992 through 2003-2004. Rates were standardized to the BC population in 2000. We used 2 definitions of OA: 1) at least 1 visit or hospitalization with a diagnostic code for OA, and 2) at least 2 visits or 1 hospitalization with a code for OA. Incidence rates were calculated with a 5-year run-in period to exclude prevalent cases.

RESULTS

Between 1996-1997 and 2003-2004, crude incidence rates of OA based on definition 1 increased from 10.5 to 12.2 per 1,000 in men and from 13.9 to 17.4 per 1,000 in women. The age-standardized rates did not change in men and increased from 14.7 to 16.7 per 1,000 in women. Incidence rates based on definition 2 were almost 50% lower, but the trends were similar.

CONCLUSION

We observed an increase in the incidence of OA in both men and women due to population aging and an additional increase in women beyond the effect of aging. These trends have important implications for public health and provision of health services to this very large group of patients.

Estimation of the period prevalence of inflammatory bowel disease among nine health plans using computerized diagnoses and outpatient pharmacy dispensings

BACKGROUND

There are few contemporary estimates of prevalence rates for inflammatory bowel disease (IBD) in diverse North American communities.

METHODS

We estimated the period prevalence of IBD for January 1, 1999, through June 30, 2001, among 1.8 million randomly sampled members of nine integrated healthcare organizations in the US using computerized diagnoses and outpatient pharmaceutical dispensing. We also assessed the positive predictive value (PPV) and sensitivities of 1) the case-finding algorithm, and 2) the 30-month sampling period using medical chart review and linkage to a 78-month dataset, respectively.

RESULTS

The PPV of the case-finding algorithm was 81% (95% confidence interval [CI], 78-87) and 84% (95% CI, 79-89) in two different organizations. In both, the sensitivity of the optimal algorithm, compared with the most inclusive, exceeded 90%. The sensitivity of the 30-month sampling period compared with 78 months was 61% (95% CI, 57-64) in one organization. Applying a slightly more sensitive case-finding algorithm, the average period prevalence of IBD across the nine organizations, standardized to the age- and gender-distribution of the US population, 2000 census, was 388 cases (95% CI, 378-397) per 100,000 persons (range 209-784 per 100,000; average follow-up 26 months). The prevalence of Crohn's disease, ulcerative colitis, and unspecified IBD was 129, 191, and 69 per 100,000, respectively.

CONCLUSIONS

The observed average prevalence was similar to prevalence proportions reported for other North American populations (369-408 per 100,000). Additional research is needed to understand differences in the occurrence of IBD among diverse populations as well as practice variation in diagnosis and treatment of IBD.

Validity of gout diagnoses in administrative data

OBJECTIVE

To determine the utility of using administrative data for epidemiologic studies of gout by examining the validity of gout diagnoses in claims data.

METHODS

From a population of approximately 800,000 members from 4 managed care plans, we identified patients who had at least 2 ambulatory claims for a diagnosis of gout between January 1, 1999 and December 31, 2003. From this group, a random sample of 200 patients was chosen for medical record review. Trained medical record reviewers abstracted gout-related clinical, laboratory, and radiologic data from the medical records. Two rheumatologists independently evaluated the abstracted information and assessed whether the gout diagnosis was probable/definite or unlikely/insufficient information. Discordant physician ratings were adjudicated by consensus. Based on record reviews, patients were also classified according to the American College of Rheumatology (ACR), Rome, and New York gout criteria and these results were compared with the physician global assessments.

RESULTS

There were 121 patients rated as having probable/definite gout by physician consensus, leading to a positive predictive value of >or=2 coded diagnoses of gout of 61% (95% confidence interval 53-67). There was low concordance between physician assessments and established gout criteria including ACR, Rome, and New York criteria (kappa = 0.17, 0.16, and 0.20, respectively).

CONCLUSION

Use of administrative data alone in epidemiologic and health services research on gout may lead to misclassification. Medical record reviews for validation of claims data may provide an inadequate gold standard to confirm gout diagnoses.

Estimating Osteoarthritis Incidence From Population-Based Administrative Health Care Databases

PURPOSE

The aim of the study is to develop a method to estimate osteoarthritis (OA) incidence by using administrative health care databases.

METHODS

Using actual counts of OA diagnoses in different periods, we generated an equation that estimated the number of new OA diagnoses based on the length of time used for excluding prevalent OA cases. Physicians billing files from 1983 to 2002 maintained at Alberta Health and Wellness were used to verify the proposed method. Age- and sex-specific and crude OA incidences in 2002 were calculated by using this method.

RESULTS

Women aged 50 to 59 years had the greatest incidence. For men, the greatest incidence was in the 60- to 69-year age category. Crude incidences for women and men were 1103 and 934 per 100,000 person-years, respectively. The overall crude rate was 1040 per 100,000 person-years.

CONCLUSIONS

Modified power function accurately summarizes the relationship between number of first OA diagnoses and length of the clearance period and thus provides an effective model to estimate OA incidence. Not restricted to OA, this model also can be implemented to estimate incidences of other chronic conditions.

Usefulness of a national hospital database to evaluate the burden of primary joint replacement for coxarthrosis and gonarthrosis in patients aged over 40 years

OBJECTIVE

To evaluate the 2001 French burden of hospital primary joint replacement (PJR) for coxarthrosis and gonarthrosis.

METHODS

Hospital surgical admissions for coxarthrosis and gonarthrosis in people aged over 40 years were selected from the French National Hospital Database. Of the 73,150 and 58,746 admissions for coxarthrosis and gonarthrosis, respectively, only 96 and 73% of them were analysed (exclusion of stays with no respect of coding guidelines). For each, we described the type of osteoarthritis, gender and age group distribution, incidence rate of PJR adjusted on age and gender, the type of joint replacement (total vs partial), the type of hospital (private vs hospital), the mean length of stay (LOS), the percentage of patients transferred to rehabilitation centre and the hospital costs.

RESULTS

Whatever the type of osteoarthritis, PJR was mainly performed for primary osteoarthritis, in the 71-80 years' age group, in private hospital, with a total replacement procedure. The mean LOS were 13 and 12 days, and the transfers to a rehabilitation centre were 33 and 44%, for hip and knee, respectively. The incident rate of PJR increased significantly with age. It was higher in the 71-80 years' age group and decreased thereafter, whatever the gender and the type of osteoarthritis. The whole hospital costs were 591 and 411 millions of euros for hip and knee, respectively.

CONCLUSION

The French National Hospital Database is a useful tool for assessing the burden of primary PJR for coxarthrosis and gonarthrosis. It might be used for international comparisons.

Impact of osteoarthritis: results of a nationwide survey of 10,000 patients consulting for OA

The clinical burden of osteoarthritis (OA) is difficult to assess because of the substantial variability between patients.

OBJECTIVE

Evaluate the human consequences of OA in patients.

METHODS

In 2000, a nationwide survey was conducted among a sample of more than 5000 physicians (90.3% general practitioners and 9.7% rheumatologists), representative of French physicians. Each recruited the first two patients consulting for hip, knee, or hand OA after the survey began. The functional limitation rates were compared with those for age- and sex-matched controls obtained from the 1999 population-based national survey on disability (HID survey).

RESULTS

Clinical and demographic information was obtained for 10,412 OA patients (mean-age 66.2 years, sex ratio F:M 1.96). The OA diagnosis was based on both clinical and radiographic findings for 84.5%. More than 80% of all patients reported limitations in their activities of daily living, either for basic tasks, leisure activities, or work. OA patients were substantially more limited than controls: the standardised limitation rate ratios (SLRR) were 6.0 (95% confidence interval: 5.9:6.1) for mobility outside the home, 2.1 (2.0:2.1) for house cleaning, 1.6 (1.5:1.8) for dressing oneself, and 1.6 (1.5:1.8) for sports. Of the 17.6% of OA patients and 17.5% of the controls still working, 64.4% and 14.3%, respectively, were limited in their job duties, for a SLRR of 4.5 (4.3:4.7).

CONCLUSION

This study shows that OA-related disability has a significant impact on the retired as well as on those still involved in the labour market.

Health services research in rheumatology: a great deal accomplished, a great deal left to do

Although rheumatology has been on the cutting edge of health services research for decades, there are many unresolved issues for patients, clinicians, insurers, and policy makers. This article explore three areas in which methodologic controversies present tradeoffs to a health care system that is grappling with larger issues around cost and access to care. Specifically, we examine issues around the use of large databases, the appropriate instruments for measuring patient-centered outcomes, and the questions that are raised from cost effectiveness studies of new treatments for rheumatoid arthritis. The issues are presented in the context of a need to provide better information to those who are providing care and those who are paying for it.

Administrative data as a tool for arthritis surveillance: estimating prevalence and utilization of services

The public health burden of arthritis and related conditions is incompletely described by commonly used public health surveillance systems. We examined the potential of administrative data as a supplement. The administrative data sources we used underestimated the prevalence of arthritis and overestimated service utilization for persons with arthritis when data from only one year were used. The use of five year's data doubled the prevalence estimate and reduced the service utilization estimate by half. The demographics of the population covered by administrative data also influence the prevalence estimate. Administrative data may usefully supplement routine public health surveillance systems but must be used with caution.

Accuracy of Medicare claims data for rheumatologic diagnoses in total hip replacement recipients

This analysis was performed to examine whether Medicare claims accurately document underlying rheumatologic diagnoses in total hip replacement (THR) recipients. We obtained data on rheumatologic diagnoses including rheumatoid arthritis (RA), avascular necrosis (AVN), and osteoarthritis (OA) from medical records and from Medicare claims data. To examine the accuracy of claims data we calculated sensitivity and positive predictive value using medical records data as the "gold standard" and assessed bias due to misclassification of claims-based diagnoses. The sensitivities of claims-based diagnoses of RA, AVN, and OA were 0.65, 0.54, and 0.96, respectively; the positive predictive values were all in the 0.86-0.89 range. The sensitivities of RA and AVN varied substantially across hospital volume strata, but in different directions for the two diagnoses. We conclude that inaccuracies in claims coding of diagnoses are frequent, and are potential sources of bias. More studies are needed to examine the magnitude and direction of bias in health outcomes research due to inaccuracy of claims coding for specific diagnoses.