Does gabapentin provide benefit for patients with knee OA? A benefit-harm and cost-effectiveness analysis.

OBJECTIVE: Gabapentin can treat neuropathic pain syndromes and has increasingly been prescribed to treat nociplastic pain. Some patients with knee osteoarthritis (OA) suffer from both nociceptive and nociplastic pain. We examined the cost-effectiveness of adding gabapentin to knee OA care. METHOD: We used the Osteoarthritis Policy Model, a validated Monte Carlo simulation of knee OA, to examine the value of gabapentin in treating knee OA by comparing three strategies: 1) usual care, gabapentin sparing (UC-GS); 2) targeted gabapentin (TG), which provides gabapentin plus usual care for those who screen positive for nociplastic pain on the modified PainDETECT questionnaire (mPD-Q) and usual care only for those who screen negative; and 3) universal gabapentin plus usual care (UG). Outcomes included cumulative quality-adjusted life years (QALYs), lifetime direct medical costs, and incremental cost-effectiveness ratios (ICERs), discounted at 3% annually. We derived model inputs from published literature and national databases and varied key input parameters in sensitivity analyses. RESULTS: UC-GS dominated both gabapentin-containing strategies, as it led to lower costs and more QALYs. TG resulted in a cost increase of $689 and a cumulative QALY reduction of 0.012 QALYs. UG resulted in a further $1,868 cost increase and 0.036 QALY decrease. The results were robust to plausible changes in input parameters. The lowest TG strategy ICER of $53,000/QALY was reported when mPD-Q specificity was increased to 100% and AE rate was reduced to 0%. CONCLUSION: Incorporating gabapentin into care for patients with knee OA does not appear to offer good value.

The burden of OA-health services and economics.

Osteoarthritis (OA) is a highly prevalent and disabling condition that affects over 7% of people globally (528 million people). Prevalence levels are even higher in countries with established market economies, which have older demographic profiles and a higher prevalence of obesity, such as the US (14%). As the 15th highest cause of years lived with disability (YLDs) worldwide, the burden OA poses to individuals is substantial, characterized by pain, activity limitations, and reduced quality of life. The economic impact of OA, which includes direct and indirect (time) costs, is also substantial, ranging from 1 to 2.5% of gross national product (GNP) in countries with established market economies. In regions around the world, the average annual cost of OA for an individual is estimated between $700-$15,600 (2019 USD). Though trends in OA prevalence vary by geography, the prevalence of OA is projected to rise in regions with established market economies such as North America and Europe, where populations are aging and the prevalence of obesity is rising.

Cost-effectiveness of duloxetine for knee OA subjects: the role of pain severity.

OBJECTIVE: Establish the impact of pain severity on the cost-effectiveness of generic duloxetine for knee osteoarthritis (OA) in the United States. DESIGN: We used a validated computer simulation of knee OA to compare usual care (UC) - intra-articular injections, opioids, and total knee replacement (TKR) - to UC preceded by duloxetine in those no longer achieving pain relief from non-steroidal anti-inflammatory drugs (NSAIDs). Outcomes included quality-adjusted life years (QALYs), lifetime medical costs, and incremental cost-effectiveness ratios (ICERs). We considered cohorts with mean ages 57-75 years and Western Ontario and McMaster Osteoarthritis Index (WOMAC) pain 25-55 (0-100, 100-worst). We derived inputs from published data. We discounted costs and benefits 3% annually. We conducted sensitivity analyses of duloxetine efficacy, duration of pain relief, toxicity, and costs. RESULTS: Among younger subjects with severe pain (WOMAC pain = 55), duloxetine led to an additional 9.6 QALYs per 1,000 subjects (ICER = $88,500/QALY). The likelihood of duloxetine being cost-effective at willingness-to-pay (WTP) thresholds of $50,000/QALY and $100,000/QALY was 40% and 54%. Offering duloxetine to older patients with severe pain led to ICERs >$150,000/QALY. Offering duloxetine to subjects with moderate pain (pain = 25) led to ICERs <$50,000/QALY, regardless of age. Among knee OA subjects with severe pain (pain = 55) who are unwilling or unable to undergo TKR, ICERs were <$50,600/QALY, regardless of age. CONCLUSIONS: Duloxetine is a cost-effective addition to knee OA UC for subjects with moderate pain or those with severe pain unable or unwilling to undergo TKR. Among younger subjects with severe pain, duloxetine is cost-effective at WTP thresholds >$88,500/QALY.

Long-term clinical and economic outcomes of a short-term physical activity program in knee osteoarthritis patients.

OBJECTIVE: Physical activity (PA) in the US knee osteoarthritis (OA) population is low, despite well-established health benefits. PA program implementation is often stymied by sustainability concerns. We sought to establish parameters that would make a short-term (3-year efficacy) PA program a cost-effective component of long-term OA care. METHOD: Using a validated computer microsimulation (Osteoarthritis Policy Model), we examined the long-term clinical (e.g., comorbidities averted), quality of life (QoL), and economic impacts of a 3-year PA program, based upon the SPARKS (Studying Physical Activity Rewards after Knee Surgery) Trial, for inactive knee OA patients. We determined the cost, efficacy, and impact of PA on QoL and medical costs that would make a PA program a cost-effective addition to OA care. RESULTS: Among the 14 million with knee OA in the US, >4 million are inactive. Participation of 10% in the modeled PA program could save 200 cases of cardiovascular disease, 400 cases of diabetes, and 6,800 quality-adjusted life-years (QALYs). The program had an incremental cost-effectiveness ratio (ICER) of $16,100/QALY. Tripling PA program cost ($860/year) raised the ICER to $108,300/QALY; varying QoL benefits from PA yielded ICERs of $8,800/QALY-$99,900/QALY; varying background cost savings from PA did not qualitatively impact ICERs. Offering the PA program to any adults with knee OA (not only inactive) yielded $31,000/QALY. CONCLUSION: A PA program with 3-year efficacy in the knee OA population carried favorable long-term clinical and economic benefits. These results offer justification for policymakers and payers considering a PA intervention incorporated into knee OA care.

Patterns of prescription opioid use before total hip and knee replacement among US Medicare enrollees.

OBJECTIVE: To examine patterns of prescription opioid use before total joint replacement (TJR) and factors associated with continuous use of opioids before TJR. DESIGN: We conducted an observational cohort study among Medicare enrollees aged ≥65 years who underwent TJR between 2010 and 2014. Preoperative opioid use was defined as having any opioid prescription in the 12-month period before TJR. Patients who had an opioid prescription every month for a 12-month period were defined as continuous users. We examined patients' demographics, pain-related conditions, medication use, other comorbidities, healthcare utilization and their association with use of opioids before TJR. RESULTS: A total of 473,781 patients underwent TJR:,155,516 THR and 318,265 TKR. Among the total cohort, 60.2% patients had any use of opioids and of those, 12.4% used opioids at least once a month continuously over the 12-month baseline period. Correlates of continuous opioid use included African American race (OR = 2.14, 95% confidence intervals (CI) = 2.01-2.28, compared to White patients), history of drug abuse (OR = 5.18, 95% CI = 3.95-6.79) and back pain (OR = 2.32, 95% CI = 2.24-2.39). CONCLUSIONS: In this large cohort of patients undergoing TJR, over 60% ever used opioids and 12.4% of them continuously used opioids in the 12-month prior to surgery. Utilization of opioids became more frequent and high-dosed near the surgery. History of drug abuse, back pain, and African American race were strongly associated with continuous use of opioids preoperatively. Further research is needed to determine short-term and long-term risks of preoperative use of opioids in TJR patients and to optimize pre- and post-TJR pain management of patients with arthritis.

Cost-effectiveness of health coaching and financial incentives to promote physical activity after total knee replacement.

OBJECTIVE: We evaluated the cost-effectiveness of Telephonic Health Coaching and Financial Incentives (THC + FI) to promote physical activity in total knee replacement recipients. DESIGN: We used the Osteoarthritis Policy Model, a computer simulation of knee osteoarthritis, to evaluate the cost-effectiveness of THC + FI compared to usual care. We derived transition probabilities, utilities, and costs from trial data. We conducted lifetime analyses from the healthcare perspective and discounted all cost-effectiveness outcomes by 3% annually. The primary outcome was the Incremental Cost-Effectiveness Ratio (ICER), defined as the ratio of the differences in costs and Quality-Adjusted Life Years (QALYs) between strategies. We considered ICERs <$100,000/QALY to be cost-effective. We conducted one-way sensitivity analyses that varied parameters across their 95% confidence intervals (CI) and limited the efficacy of THC + FI to 1 year or to 9 months. We also conducted a probabilistic sensitivity analysis (PSA), simultaneously varying cost, utilities, and transition probabilities. RESULTS: THC + FI had an ICER of $57,200/QALY in the base case and an ICER below $100,000/QALY in most deterministic sensitivity analyses. THC + FI cost-effectiveness depended on assumptions about long-term efficacy; when efficacy was limited to 1 year or to 9 months, the ICER was $93,300/QALY or $121,800/QALY, respectively. In the PSA, THC + FI had an ICER below $100,000/QALY in 70% of iterations. CONCLUSIONS: Based on currently available information, THC + FI might be a cost-effective alternative to usual care. However, the uncertainty surrounding this choice is considerable, and further research to reduce this uncertainty may be economically justified.

International assessment on quality and content of internet information on osteoarthritis.

OBJECTIVE: Osteoarthritis is one of the leading causes of global disability. Numerous studies have assessed the quality and content of online health information; however, how information content varies between multiple countries remains unknown. The primary objective of this study was to examine how the quality and content of online health information on osteoarthritis compares on an international scale. METHODS: Internet searches for the equivalent of "knee osteoarthritis treatment" were performed in ten countries around the world. For each country, the first ten websites were evaluated using a custom scoring form examining: website type; quality and reliability using the DISCERN and Health-on-the-Net (HON) frameworks; and treatment content based on three international osteoarthritis treatment guidelines. Consistency of search results between countries speaking the same language was also assessed. RESULTS: Significant differences in all scoring metrics existed between countries speaking different languages. Western countries scored higher than more eastern countries, there were no differences between the United States and Mexico in any of the scoring metrics, and HON certified websites were of higher quality and reliability. Searches in different countries speaking the same language had at least 70% overlap. CONCLUSIONS: The quality of online health information on knee osteoarthritis varies significantly between countries speaking different languages. Differential access to quality, accurate, and safe health information online may represent a novel but important health inequality. Future efforts are needed to translate online health resources into additional languages. In the interim, patients may seek websites that display the HON seal.

Cost-effectiveness of generic celecoxib in knee osteoarthritis for average-risk patients: a model-based evaluation.

OBJECTIVE: The cost-effectiveness of the recently-introduced generic celecoxib in knee OA has not been examined. METHOD: We used the Osteoarthritis Policy (OAPol) Model, a validated computer simulation of knee OA, to evaluate long-term clinical outcomes, costs, and cost-effectiveness of generic celecoxib in persons with knee OA. We examined eight treatment strategies consisting of generic celecoxib, over-the-counter (OTC) naproxen, or prescription naproxen, with or without prescription or OTC proton-pump-inhibitors (PPIs) to reduce gastrointestinal (GI) toxicity. In the base case, we assumed that annual cost was $130 for OTC naproxen, $360 for prescription naproxen, and $880 for generic celecoxib. We considered a willingness-to-pay threshold of $100,000 per quality-adjusted life year (QALY) and discounted costs and benefits at 3% annually. In sensitivity analyses we varied celecoxib toxicity, discontinuation, cost, and pain level. RESULTS: In the base case analysis of the high pain cohort (WOMAC 50), celecoxib had an incremental cost-effectiveness ratio (ICER) of $284,630/QALY compared with OTC naproxen. Only under highly favorable cost, toxicity, and discontinuation assumptions (e.g., annual cost below $360, combined with a reduction in the cardiovascular (CV) event rates below baseline values) was celecoxib likely to be cost-effective. Celecoxib might also be cost-effective at an annual cost of $600 if CV toxicity were eliminated completely. In subjects with moderate pain (WOMAC 30), at the base case CV event rate of 0.2%, generic celecoxib was only cost-effective at the lowest plausible cost ($190). CONCLUSION: In knee OA patients with no comorbidities, generic celecoxib is not cost-effective at its current price.

Model-based evaluation of cost-effectiveness of nerve growth factor inhibitors in knee osteoarthritis: impact of drug cost, toxicity, and means of administration.

OBJECTIVE: Studies suggest nerve growth factor inhibitors (NGFi) relieve pain but may accelerate disease progression in some patients with osteoarthritis (OA). We sought cost and toxicity thresholds that would make NGFi a cost-effective treatment for moderate-to-severe knee OA. DESIGN: We used the Osteoarthritis Policy (OAPol) model to estimate the cost-effectiveness of NGFi compared to standard of care (SOC) in OA, using Tanezumab as an example. Efficacy and rates of accelerated OA progression were based on published studies. We varied the price/dose from $200 to $1000. We considered self-administered subcutaneous (SC) injections (no administration cost) vs provider-administered intravenous (IV) infusion ($69-$433/dose). Strategies were defined as cost-effective if their incremental cost-effectiveness ratio (ICER) was less than $100,000/quality-adjusted life year (QALY). In sensitivity analyses we varied efficacy, toxicity, and costs. RESULTS: SOC in patients with high levels of pain led to an average discounted quality-adjusted life expectancy of 11.15 QALYs, a lifetime risk of total knee replacement surgery (TKR) of 74%, and cumulative discounted direct medical costs of $148,700. Adding Tanezumab increased QALYs to 11.42, reduced primary TKR utilization to 63%, and increased costs to between $155,400 and $199,500. In the base-case analysis, Tanezumab at $600/dose was cost-effective when delivered outside of a hospital. At $1000/dose, Tanezumab was not cost-effective in all but the most optimistic scenario. Only at rates of accelerated OA progression of 10% or more (10-fold higher than reported values) did Tanezumab decrease QALYs and fail to represent a viable option. CONCLUSIONS: At $100,000/QALY, Tanezumab would be cost effective if priced ≤$400/dose in all settings except IV hospital delivery.

Cost-effectiveness of nonsteroidal anti-inflammatory drugs and opioids in the treatment of knee osteoarthritis in older patients with multiple comorbidities.

OBJECTIVE: To evaluate long-term clinical and economic outcomes of naproxen, ibuprofen, celecoxib or tramadol for OA patients with cardiovascular disease (CVD) and diabetes. DESIGN: We used the Osteoarthritis Policy Model to examine treatment with these analgesics after standard of care (SOC) - acetaminophen and corticosteroid injections - failed to control pain. NSAID regimens were evaluated with and without proton pump inhibitors (PPIs). We evaluated over-the-counter (OTC) regimens where available. Estimates of treatment efficacy (pain reduction, occurring in ∼57% of patients on all regimens) and toxicity (major cardiac or gastrointestinal toxicity or fractures, risk ranging from 1.09% with celecoxib to 5.62% with tramadol) were derived from published literature. Annual costs came from Red Book Online(®). Outcomes were discounted at 3%/year and included costs, quality-adjusted life expectancy, and incremental cost-effectiveness ratios (ICERs). Key input parameters were varied in sensitivity analyses. RESULTS: Adding ibuprofen to SOC was cost saving, increasing QALYs by 0.07 while decreasing cost by $800. Incorporating OTC naproxen rather than ibuprofen added 0.01 QALYs and increased costs by $300, resulting in an ICER of $54,800/QALY. Using prescription naproxen with OTC PPIs led to an ICER of $76,700/QALY, while use of prescription naproxen with prescription PPIs resulted in an ICER of $252,300/QALY. Regimens including tramadol or celecoxib cost more but added fewer QALYs and thus were dominated by several of the naproxen-containing regimens. CONCLUSIONS: In patients with multiple comorbidities, naproxen- and ibuprofen-containing regimens are more effective and cost-effective in managing OA pain than opioids, celecoxib or SOC.

Pharmacologic regimens for knee osteoarthritis prevention: can they be cost-effective?

OBJECTIVE: We sought to determine the target populations and drug efficacy, toxicity, cost, and initiation age thresholds under which a pharmacologic regimen for knee osteoarthritis (OA) prevention could be cost-effective. DESIGN: We used the Osteoarthritis Policy (OAPol) Model, a validated state-transition simulation model of knee OA, to evaluate the cost-effectiveness of using disease-modifying OA drugs (DMOADs) as prophylaxis for the disease. We assessed four cohorts at varying risk for developing OA: (1) no risk factors, (2) obese, (3) history of knee injury, and (4) high-risk (obese with history of knee injury). The base case DMOAD was initiated at age 50 with 40% efficacy in the first year, 5% failure per subsequent year, 0.22% major toxicity, and annual cost of $1,000. Outcomes included costs, quality-adjusted life expectancy (QALE), and incremental cost-effectiveness ratios (ICERs). Key parameters were varied in sensitivity analyses. RESULTS: For the high-risk cohort, base case prophylaxis increased quality-adjusted life-years (QALYs) by 0.04 and lifetime costs by $4,600, and produced an ICER of $118,000 per QALY gained. ICERs >$150,000/QALY were observed when comparing the base case DMOAD to the standard of care in the knee injury only cohort; for the obese only and no risk factors cohorts, the base case DMOAD was less cost-effective than the standard of care. Regimens priced at $3,000 per year and higher demonstrated ICERs above cost-effectiveness thresholds consistent with current US standards. CONCLUSIONS: The cost-effectiveness of DMOADs for OA prevention for persons at high risk for incident OA may be comparable to other accepted preventive therapies.

Studies of pain management in osteoarthritis: bedside to policy.

OBJECTIVE: Osteoarthritis (OA) is a debilitating chronic condition requiring long-term treatment of pain and functional impairment. Our objective was to characterize studies addressing management of OA-related pain with respect to the breadth of interventions, trial duration and size, outcome measures, and funding sources. DESIGN: We identified studies focused on 'pain' and 'osteoarthritis' from ClinicalTrals.gov and abstracted data on study status, sample size, design, funding source, duration, outcomes measured, and interventions evaluated. We examined associations among intervention type, funding source, sample size, duration, and outcomes measured. RESULTS: We identified 287 registered studies, of which 69% investigated pharmacologic interventions, 11% behavioral interventions, and 5% surgical procedures or devices, while the remainder examined other types of interventions. Eighty-seven percent evaluated knee OA. The average sample size was 290 subjects and average study duration was 7.4 months, with 52% using durations ≤3 months and 21% ≥12 months. Industry funded 64% of studies, either fully or partially. Of 180 completed studies, 139 were pharmacologic studies. Of these, 34 (24%) posted results to the registry. Among the studies funded by industry, 60% had durations ≤3 months as compared with 36% among non-industry funded studies (P < 0.0001). Behavioral intervention trials tended to be of longer duration than pharmacologic trials and were less likely to be funded by industry. CONCLUSION: Over half of OA pain studies and >80% of those funded by industry used trial durations of less than 6 months. Future studies should take into consideration the need for long-term pain management for OA when designing trial protocols.

A rapid, novel method of volumetric assessment of MRI-detected subchondral bone marrow lesions in knee osteoarthritis.

PURPOSE: To assess reliability and validity of a semi-automated quantitative method for osteoarthritis (OA)-related bone marrow lesion (BML) assessment in the femur and tibia. METHODS: In a cross-sectional study of subjects with knee OA, we examined concurrent criterion and clinical validation of a novel method of semi-automated quantitative BML measurement. The primary outcome was total segmented BML volume in femoral and tibial medial and lateral knee compartments. Criterion validation was examined through comparison of BML volumes with Whole-Organ Magnetic Resonance Imaging Score (WORMS) scoring. Clinical validation was examined via associations of tibial and femoral BML volume with the Western Ontario and McMaster University OA Index weight-bearing pain questions. RESULTS: Among the 115 subjects, mean age was 62 years, mean BMI 30.4 (kg/m(2)), 84% were white and 52% male. The intra-class correlation coefficients (ICC) for intra-reader reliability was 0.96 and 0.97 for inter-reader reliability. Significant Spearman's correlations were found between segmented BML volume and WORMS BML scoring for tibial medial (0.75) and lateral (0.73) compartments, and for femoral medial (0.72) and lateral (0.88) compartments. Significant positive associations were found between weight-bearing pain and total femoral BML volume (P < 0.003), but not total tibial BML (P < 0.101). CONCLUSION: We have documented a moderately strong correlation between a novel measurement method of femoral and tibial BML volume and semi-quantitative WORMS scores, providing evidence of criterion validity. The hypothesis that weight-bearing pain was associated with BML volume was confirmed for total femoral BML volume but not total tibial BML volume. The lack of association between tibial BML volume and pain requires further investigation.

Disease-modifying drugs for knee osteoarthritis: can they be cost-effective?

OBJECTIVE: Disease-modifying osteoarthritis drugs (DMOADs) are under development. Our goal was to determine efficacy, toxicity, and cost thresholds under which DMOADs would be a cost-effective knee OA treatment. DESIGN: We used the Osteoarthritis Policy Model, a validated computer simulation of knee OA, to compare guideline-concordant care to strategies that insert DMOADs into the care sequence. The guideline-concordant care sequence included conservative pain management, corticosteroid injections, total knee replacement (TKR), and revision TKR. Base case DMOAD characteristics included: 50% chance of suspending progression in the first year (resumption rate of 10% thereafter) and 30% pain relief among those with suspended progression; 0.5%/year risk of major toxicity; and costs of $1,000/year. In sensitivity analyses, we varied suspended progression (20-100%), pain relief (10-100%), major toxicity (0.1-2%), and cost ($1,000-$7,000). Outcomes included costs, quality-adjusted life expectancy, incremental cost-effectiveness ratios (ICERs), and TKR utilization. RESULTS: Base case DMOADs added 4.00 quality-adjusted life years (QALYs) and $230,000 per 100 persons, with an ICER of $57,500/QALY. DMOADs reduced need for TKR by 15%. Cost-effectiveness was most sensitive to likelihoods of suspended progression and pain relief. DMOADs costing $3,000/year achieved ICERs below $100,000/QALY if the likelihoods of suspended progression and pain relief were 20% and 70%. At a cost of $5,000, these ICERs were attained if the likelihoods of suspended progression and pain relief were both 60%. CONCLUSIONS: Cost, suspended progression, and pain relief are key drivers of value for DMOADs. Plausible combinations of these factors could reduce need for TKR and satisfy commonly cited cost-effectiveness criteria.

Measuring quality of care for rheumatic diseases using an electronic medical record.

OBJECTIVES: The objective of this study was twofold: (1) to determine how best to measure adherence with time-dependent quality indicators (QIs) related to laboratory monitoring, and (2) to assess the accuracy and efficiency of gathering QI adherence information from an electronic medical record (EMR). METHODS: A random sample of 100 patients were selected who had at least three visits with the diagnosis of rheumatoid arthritis (RA) at Brigham and Women's Hospital Arthritis Center in 2005. Using the EMR, it was determined whether patients had been prescribed a disease-modifying antirheumatic drug (DMARD) (QI #1) and if patients starting therapy received appropriate baseline laboratory testing (QI #2). For patients consistently prescribed a DMARD, adherence with follow-up testing (QI #3) was calculated using three different methods, the Calendar, Interval and Rolling Interval METHOD: . RESULTS: It was found that 97% of patients were prescribed a DMARD (QI #1) and baseline tests were completed in 50% of patients (QI #2). For follow-up testing (QI #3), mean adherence was 60% for the Calendar Method, 35% for the Interval Method, and 48% for the Rolling Interval Method. Using the Rolling Interval Method, adherence rates were similar across drug and laboratory testing type. CONCLUSIONS: Results for adherence with laboratory testing QIs for DMARD use differed depending on how the QIs were measured, suggesting that care must be taken in clearly defining methods. While EMRs will provide important opportunities for measuring adherence with QIs, they also present challenges that must be examined before widespread adoption of these data collection methods.

Work pattern causes bias in self-reported activity duration: a randomised study of mechanisms and implications for exposure assessment and epidemiology.

BACKGROUND: Self-reported activity duration is used to estimate cumulative exposures in epidemiological research. OBJECTIVE: The effects of work pattern, self-reported task dullness (a measure of cognitive task demand), and heart rate ratio and perceived physical exertion (measures of physical task demands) on error in task duration estimation were investigated. METHODS: 24 participants (23-54 years old, 12 males) were randomly assigned to execute three tasks in either a continuous (three periods of 40 continuous minutes, one for each task) or a discontinuous work pattern (40 min tasks each divided into four periods of 4, 8, 12 and 16 min). Heart rate was measured during tasks. After completing the 2 h work session, subjects reported the perceived duration, dullness and physical exertion for each of the three tasks. Multivariate models were fitted to analyse errors and their absolute value to assess the accuracy in task duration estimation and the mediating role of task demands on the observed results. RESULTS: Participants overestimated the time spent shelving boxes (up to 38%) and filing journals (up to 9%), and underestimated the time typing articles (up to -22%). Over- and underestimates and absolute errors were greater in the discontinuous work pattern group. Only the self-reported task dullness mediated the differences in task duration estimation accuracy between work patterns. CONCLUSIONS: Task-related factors can affect self-reported activity duration. Exposure assessment strategies requiring workers to allocate work time to different tasks could result in biased measures of association depending on the demands of the tasks during which the exposure of interest occurs.

Association between hospital and surgeon procedure volume and outcomes of total hip replacement in the United States medicare population.

BACKGROUND: The mortality and complication rates of many surgical procedures are inversely related to hospital procedure volume. The objective of this study was to determine whether the volumes of primary and revision total hip replacements performed at hospitals and by surgeons are associated with rates of mortality and complications. METHODS: We analyzed claims data of Medicare recipients who underwent elective primary total hip replacement (58,521 procedures) or revision total hip replacement (12,956 procedures) between July 1995 and June 1996. We assessed the relationship between surgeon and hospital procedure volume and mortality, dislocation, deep infection, and pulmonary embolus in the first ninety days postoperatively. Analyses were adjusted for age, gender, arthritis diagnosis, comorbid conditions, and income. Analyses of hospital volume were adjusted for surgeon volume, and analyses of surgeon volume were adjusted for hospital volume. RESULTS: Twelve percent of all primary total hip replacements and 49% of all revisions were performed in centers in which ten or fewer of these procedures were carried out in the Medicare population annually. In addition, 52% of the primary total hip replacements and 77% of the revisions were performed by surgeons who carried out ten or fewer of these procedures annually. Patients treated with primary total hip replacement in hospitals in which more than 100 of the procedures were performed per year had a lower risk of death than those treated with primary replacement in hospitals in which ten or fewer procedures were performed per year (mortality rate, 0.7% compared with 1.3%; adjusted odds ratio, 0.58; 95% confidence interval, 0.38, 0.89). Patients treated with primary total hip replacement by surgeons who performed more than fifty of those procedures in Medicare beneficiaries per year had a lower risk of dislocation than those who were treated by surgeons who performed five or fewer of the procedures per year (dislocation rate, 1.5% compared with 4.2%; adjusted odds ratio, 0.49; 95% confidence interval, 0.34, 0.69). Patients who had revision total hip replacement done by surgeons who performed more than ten such procedures per year had a lower rate of mortality than patients who were treated by surgeons who performed three or fewer of the procedures per year (mortality rate, 1.5% compared with 3.1%; adjusted odds ratio, 0.65; 95% confidence interval, 0.44, 0.96). CONCLUSIONS: Patients treated at hospitals and by surgeons with higher annual caseloads of primary and revision total hip replacement had lower rates of mortality and of selected complications. These analyses of Medicare claims are limited by a lack of key clinical information such as operative details and preoperative functional status.