Hiraku Kumamaru

Validity of Claims-Based Stroke Algorithms in Contemporary Medicare Data Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study Linked With Medicare Claims

Background—The accuracy of stroke diagnosis in administrative claims for a contemporary population of Medicare enrollees has not been studied. We assessed the validity of diagnostic coding algorithms for identifying stroke in the Medicare population by linking data from the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study to Medicare claims. Methods and Results—The REGARDS Study enrolled 30 239 participants ≥45 years in the United States between 2003 and 2007. Stroke experts adjudicated suspected strokes, using retrieved medical records. We linked data for participants enrolled in fee-for-service Medicare to claims files from 2003 through 2009. Using adjudicated strokes as the gold standard, we calculated accuracy measures for algorithms to identify incident and recurrent strokes. We linked data for 15 089 participants, among whom 422 participants had adjudicated strokes during follow-up. An algorithm using primary discharge diagnosis codes for acute ischemic or hemorrhagic stroke (International Classification of Diseases, Ninth Revision, Clinical Modification codes: 430, 431, 433.x1, 434.x1, 436) had a positive predictive value of 92.6% (95% confidence interval, 88.8%–96.4%), a specificity of 99.8% (99.6%–99.9%), and a sensitivity of 59.5% (53.8%–65.1%). An algorithm using only acute ischemic stroke codes (433.x1, 434.x1, 436) had a positive predictive value of 91.1% (95% confidence interval, 86.6%–95.5%), a specificity of 99.8% (99.7%–99.9%), and a sensitivity of 58.6% (52.4%–64.7%). Conclusions—Claims-based algorithms to identify stroke in a contemporary Medicare cohort had high positive predictive value and specificity, supporting their use as outcomes for etiologic and comparative effectiveness studies in similar populations. These inpatient algorithms are unsuitable for estimating stroke incidence because of low sensitivity.

Surgeon Case Volume and 30-Day Mortality After Carotid Endarterectomy Among Contemporary Medicare Beneficiaries Before and After National Coverage Determination for Carotid Artery Stenting

Background and Purpose— After the 2005 National Coverage Determination to reimburse carotid artery stenting (CAS) for Medicare beneficiaries, the number of CAS procedures increased and carotid endarterectomy (CEA) decreased. We evaluated trends in surgeons’ past-year CEA case-volume and 30-day mortality after CEA, and their association before and after the National Coverage Determination. Methods— In a retrospective cohort study of patients undergoing CEA (2001–2008) and CAS (2005–2008) using Medicare data, we described yearly trends of CEA and CAS rates, patient characteristics, and 30-day mortality after CEA. We used logistic regression adjusting for patient- and surgeon-level factors to assess the effect of surgeon case volume on 30-day mortality after CEA. Results— We identified 454 717 CEA and 27 943 CAS patients. Patients undergoing CEA in recent years were older and had more comorbidities than earlier years. CEA rates per 10 000 beneficiaries declined from 18.1 in 2002 to 12.7 in 2008, whereas median surgeon past-year case-volume declined from 27 to 21. The CAS rates peaked at 2.3 per 10 000 beneficiaries in 2006 but declined to 1.8 in 2008, resulting in declining overall revascularization procedure rates during 2005 to 2008. Thirty day post-CEA mortality was 1.40% (95% confidence interval, 1.34–1.47) in 2001 to 2002 and 1.17% (1.10–1.24) in 2007 to 2008. Surgeon’s past-year case-volume of <10 was associated with higher 30-day mortality consistently during 2001 to 2008. Conclusions— The rate of CEA procedures decreased substantially during 2001 to 2008, as did surgeon past-year case-volume. The postprocedural mortality in Medicare beneficiaries was high compared with trial patients but somewhat improved over time. Those operated by lower past-year case-volume surgeons had increased mortality.

The association of hospital volume with mortality and costs of care for stroke in Japan

Background:The association between hospital volume and patient outcomes remains unclear for stroke. Little is known about whether these relationships differ by stroke subtypes. Objectives:To examine the association of hospital volume with in-hospital mortality and costs of care for stroke. Research Design:Secondary data analysis of national hospital database. Subjects:A total of 66,406 patients admitted between July 1 and December 31, 2010 with primary diagnosis of stroke at 796 acute care hospitals in Japan were included. Measures:We used a locally weighted scatter-plot smoothing method to test the relationship between hospital volume and outcomes. On the basis of these results, we categorized patient volume into 3 groups (10–50, 51–100, and >100 discharges/6 mo). We tested the volume-outcome relationship using multivariable regression models adjusting for patient and hospital characteristics. Subgroup analysis was conducted by stratifying on stroke subtype. Results:Compared with those treated at high-volume hospitals (>100 discharges), patients admitted to low-volume hospitals (10–50 discharges) had higher in-hospital mortality (adjusted odds ratio, 1.45; 95% CI, 1.23–1.71, P<0.0001). In the lowest volume hospitals, adjusted costs of care per discharge were 8.0% lower (95% CI, −14.1% to −1.8%, P=0.01) compared with the highest volume hospitals. The volume-mortality association was significant across all stroke subtypes. Highest volume hospitals had higher costs than lowest volume hospitals for subarachnoid hemorrhage, but this association was nonsignificant for ischemic and hemorrhagic stroke. Conclusions:Highest volume hospitals had lower mortality than the lowest volume hospitals for stroke in Japan. Highest volume hospitals had higher costs for subarachnoid hemorrhage, but not for ischemic and hemorrhagic stroke.

Correlation Between Early Direct Communication of Positive CT Pulmonary Angiography Findings and Improved Clinical Outcomes

BACKGROUND Despite a general consensus that rapid communication of critical radiology findings from radiologists to referring physicians is imperative, a possible association with superior patient outcomes has not been confirmed. The objective of this study was to evaluate the correlation between early direct communication of CT image findings by radiologists to referring physicians and better clinical outcomes in patients with acute pulmonary embolism (PE). METHODS This was a retrospective, single-institution, cohort study that included 796 consecutive patients (February 2006 to March 2010) who had acute PE confirmed by CT pulmonary angiography (CTPA) and whose treatment had not been initiated at the time of CTPA acquisition. The time from CTPA to direct communication of the diagnosis was evaluated for its association with time from CTPA to treatment initiation and with 30-day mortality. Cox regression analysis was performed with inverse probability weighting by propensity scores calculated using 20 potential confounding factors. RESULTS In 93.4% of patients whose first treatment was anticoagulation, the referring physicians started treatment after receiving direct notification of the diagnosis from the radiologist. Late communication (> 1.5 h after CTPA; n = 291) was associated with longer time to treatment initiation (adjusted hazard ratio [HR], 0.714; 95% CI, 0.610-0.836; P < .001) and higher all-cause and PE-related 30-day mortality (HR, 1.813; 95% CI, 1.163-2.828; P = .009; and HR, 2.625; 95% CI, 1.362-5.059; P = .004, respectively). CONCLUSIONS Delay (> 1.5 h of CTPA acquisition) in direct communication of acute PE diagnosis from radiologists to referring physicians was significantly correlated with a higher risk of delayed treatment initiation and death within 30 days.

Causes of death and mortality and evaluation of prognostic factors in patients with severe aortic stenosis in an aging society.

BACKGROUND Severe aortic stenosis (AS) is now predominantly a disease of the elderly, with significant mortality and morbidity. In order to investigate the burden of severe AS in the current population, we assessed mortality, causes of death, clinical event rates, and prognostic factors of patients diagnosed with severe AS. METHODS A total of 519 consecutive patients (mean age, 78±9 years) with severe AS (aortic valve area <1.0 cm(2)) were retrospectively analyzed. All-cause mortality and clinical events including aortic valve replacement, heart failure requiring admission, acute coronary syndrome, and syncope were measured as main outcome. RESULTS During a median follow-up of 3.5 years, 167 patients (32%) died. Overall survival rates at 1 and 3 years were 86% and 70%, respectively. Of all deaths, 101 (61%) were cardiovascular-related and 56 (33%) were non-cardiovascular. Syncope occurred in only 18 (4%) patients, while heart failure requiring admission occurred in 188 (43%) patients as the most frequent event. Male, severe symptoms (New York Heart Association functional class, III/IV), inactive state, previous history of heart failure, renal insufficiency, hemodialysis treatment, peripheral vascular disease, malignancy, and statin use at enrollment were significantly and independently associated with death among the patients. CONCLUSIONS Among the one-third of severe AS patients who died during follow-up, 61% of deaths were cardiovascular-related. Cardiovascular death may be the leading, but not the only, cause of death for contemporary severe AS patients. Factors such as severe symptomatic status, lower daily activity level, and chronic kidney diseases were strong predictive factors of worse survival in this population.

Comparison of high-dimensional confounder summary scores in comparative studies of newly marketed medications

OBJECTIVE To compare confounding adjustment by high-dimensional propensity scores (hdPSs) and historically developed high-dimensional disease risk scores (hdDRSs) in three comparative study examples of newly marketed medications: (1) dabigatran vs. warfarin on major hemorrhage; (2) on death; and (3) cyclooxygenase-2 inhibitors vs. nonselective nonsteroidal anti-inflammatory drugs on gastrointestinal bleeds. STUDY DESIGN AND SETTING In each example, we constructed a concurrent cohort of new and old drug initiators using US claims databases. In historical cohorts of old drug initiators, we developed hdDRS models including investigator-specified plus empirically identified variables and using principal component analysis and lasso regression for dimension reduction. We applied the models to the concurrent cohorts to obtain predicted outcome probabilities, which we used for confounding adjustment. We compared the resulting estimates to those from hdPS. RESULTS The crude odds ratio (OR) comparing dabigatran to warfarin was 0.52 (95% confidence interval: 0.37-0.72) for hemorrhage and 0.38 (0.26-0.55) for death. Decile stratification yielded an OR of 0.64 (0.46-0.90) for hemorrhage using hdDRS vs. 0.70 (0.49-1.02) for hdPS. ORs for death were 0.69 (0.45-1.06) and 0.73 (0.48-1.10), respectively. The relative performance of hdDRS in the cyclooxygenase-2 inhibitors example was similar. CONCLUSION hdDRS achieved similar or better confounding adjustment compared to conventional regression approach but worked slightly less well than hdPS.

Risk factors of serious postoperative complications after pancreaticoduodenectomy and risk calculators for predicting postoperative complications: a nationwide study of 17,564 patients in Japan

The morbidity rate after pancreaticoduodenectomy remains high. The objectives of this retrospective cohort study were to clarify the risk factors associated with serious morbidity (Clavien–Dindo classification grades IV–V), and create complication risk calculators using the Japanese National Clinical Database.

Comparative Effectiveness of Carotid Artery Stenting Versus Carotid Endarterectomy Among Medicare Beneficiaries

Background—Effectiveness of carotid artery stenting (CAS) relative to carotid endarterectomy (CEA) among Medicare patients has not been established. We compared effectiveness of CAS versus CEA among Medicare beneficiaries. Methods and Results—We linked Medicare data (2000–2009) to the Society for Vascular Surgery’s Vascular Registry (2005–2008) and the National Cardiovascular Data Registrys (NCDR) Carotid Artery Revascularization and Endarterectomy Registry (2006–2008/2009). Medicare patients were followed up from procedure date until death, stroke/transient ischemic attack, periprocedural myocardial infarction, or a composite end point for these outcomes. We derived high-dimensional propensity scores using registry and Medicare data to control for patient factors and adjusted for provider factors in a Cox regression model comparing CAS with CEA. Among 5254 Society for Vascular Surgery’s Vascular Registry (1999 CAS; 3255 CEA) and 4055 Carotid Artery Revascularization and Endarterectomy Registry (2824 CAS; 1231 CEA) Medicare patients, CAS patients had a higher comorbidity burden and were more likely to be at high surgical risk (Society for Vascular Surgery’s Vascular Registry: 96.7% versus 44.5%; Carotid Artery Revascularization and Endarterectomy Registry: 71.3% versus 44.7%). Unadjusted outcome risks were higher for CAS. Mortality risks remained elevated for CAS after adjusting for patient-level factors (hazard ratio, 1.24; 95% confidence interval, 1.06–1.46). After further adjustment for provider factors, differences between CAS and CEA were attenuated or no longer present (hazard ratio for mortality, 1.13; 95% confidence interval, 0.94–1.37). Performance was comparable across subgroups defined by sex and degree of carotid stenosis, but there was a nonsignificant trend suggesting a higher risk of adverse outcomes in older (>80) and symptomatic patients undergoing CAS. Conclusions—Outcomes after CAS and CEA among Medicare beneficiaries were comparable after adjusting for both patient- and provider-level factors.

Relationship Between Physician and Hospital Procedure Volume and Mortality After Carotid Artery Stenting Among Medicare Beneficiaries

Background—Clinical trials demonstrated the efficacy of carotid artery stenting (CAS) relative to carotid endarterectomy when performed by physicians with demonstrated proficiency. It is unclear how CAS performance may be influenced by the diversity in CAS and non-CAS provider volumes in routine clinical practice. Methods and Results—We linked Medicare claims to the Centers for Medicare and Medicaid Services’ CAS Database (2005–2009). We assessed the association between 30-day mortality and past-year physician (0, 1–4, 5–9, 10–19, ≥20) and hospital (<10, 10–19, 20–39, ≥40) CAS volumes and past-year hospital coronary and peripheral stenting volumes (<200, 200–399, 400–849, ≥850) among beneficiaries at least 66 years of age. Unadjusted 30-day mortality risk was 1.8% (95% confidence interval [CI], 1.6–2.0) for 19 724 patients undergoing CAS by 2045 physicians in 729 hospitals. Median past-year CAS volume was 9 (interquartile range, 4–19) for physicians and 23 (interquartile range, 12–41) for hospitals. Compared to physicians performing ≥20 CAS in the past year, lower CAS volumes were associated with higher adjusted risks of 30-day morality (P value for trend < 0.05): 1.4 (95% CI, 0.9–2.3) for 0 past-year CAS, 1.3 (95% CI, 0.9–1.8) for 1 to 4, 1.1 (95% CI, 0.8–1.6) for 5 to 9, and 0.9 (95% CI, 0.7–1.4) for 10 to 19. An inverse relationship between 30-day mortality and past-year CAS hospital volume as well as past-year hospital non-CAS volume, past-year hospital non-CAS volume, and 30-day mortality was also noted. Conclusions—Among Medicare patients, an inverse relationship exists between physician and hospital CAS volumes and hospital non-CAS stenting volume and 30-day mortality, even after adjusting for all pertinent patient- and hospital-level factors.

Morbidity and mortality from a propensity score-matched, prospective cohort study of laparoscopic versus open total gastrectomy for gastric cancer: data from a nationwide web-based database

BackgroundControversy persists regarding the technical feasibility of laparoscopic total gastrectomy (LTG), and to our knowledge, no prospective study with a sample size sufficient to investigate its safety has been reported. We aimed to compare the postoperative morbidity and mortality rates in patients undergoing LTG and open total gastrectomy (OTG) for gastric cancer in prospectively enrolled cohort using nationwide web-based registry.MethodsFrom August 2014 to July 2015, consecutive patients undergoing LTG or OTG (925 and 1569 patients, respectively) at the participating institutions were enrolled prospectively into the National Clinical Database registration system. We constructed propensity score (PS) models separately in four facility yearly case-volume groups, and evaluated the postoperative morbidity and mortality in PS-matched 1024 patients undergoing LTG or OTG.ResultsThe incidence of overall morbidity were 84 (16.4%) in the OTG and 54 (10.3%) in the LTG groups (p = 0.01).The incidence of anastomotic leakage and pancreatic fistula grade B or above were not significantly different between the two groups (LTG 5.3% vs. OTG 6.1%, p = 0.59, LTG 2.7% vs. OTG 3.7%, p = 0.38, respectively). There were also no significant differences in the 30-day and in-hospital mortality rates between the two groups (LTG 0.2% vs. OTG 0.4%, p = 0.56; LTG 0.4% vs. OTG 0.4%, p = 1.00, respectively).ConclusionThe results from our nationally representative data analysis showed that LTG could be a safe procedure to treat gastric cancer compared to OTG. The indication for LTG should be considered carefully in a clinical setting.