Race, ethnicity, and state-by-state geographic variation in hemorrhagic stroke in dialysis patients

BACKGROUND AND OBJECTIVES

Geographic variation in stroke rates is well established in the general population, with higher rates in the South than in other areas of the United States. A similar pattern of geographic variation in ischemic strokes has also recently been reported in patients undergoing long-term dialysis, but whether this is also the case for hemorrhagic stroke is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Medicare claims from 2000 to 2005 were used to ascertain hemorrhagic stroke events in a large cohort of incident dialysis patients. A Poisson generalized linear mixed model was generated to determine factors associated with stroke and to ascertain state-by-state geographic variability in stroke rates by generating observed-to-expected (O/E) adjusted rate ratios (ARRs) for stroke.

RESULTS

A total of 265,685 Medicare-eligible incident dialysis patients were studied. During a median follow-up of 15.5 months, 2397 (0.9%) patients sustained a hemorrhagic stroke. African Americans (ARR, 1.43; 95% confidence interval [CI], 1.30 to 1.57), Hispanics (ARR, 1.78; 95% CI, 1.57 to 2.03), and individuals of other races (ARR, 1.51; 95% CI, 1.26 to 1.80) had a significantly higher risk for hemorrhagic stroke compared with whites. In models adjusted for age and sex, four states had O/E ARRs for hemorrhagic stroke that were significantly greater than 1.0 (California, 1.15; Maryland, 1.25; North Carolina, 1.25; Texas, 1.19), while only 1 had an ARR less than 1.0 (Wisconsin, 0.79). However, after adjustment for race and ethnicity, no states had ARRs that varied significantly from 1.0.

CONCLUSION

Race and ethnicity, or other factors that covary with these, appear to explain a substantial portion of state-by-state geographic variation in hemorrhagic stroke. This finding suggests that the factors underlying the high rate of hemorrhagic strokes in dialysis patients are likely to be system-wide and that further investigations into regional variations in clinical practices are unlikely to identify large opportunities for preventive interventions for this disorder.

Development of an ambulatory geriatrics knowledge examination for internal medicine residents

BACKGROUND

The number of older adults needing primary care exceeds the capacity of trained geriatricians to accommodate them. All physicians should have basic knowledge of optimal outpatient care of older adults to enhance the capacity of the system to serve this patient group. To date, there is no knowledge-assessment tool that focuses specifically on geriatric ambulatory care.

OBJECTIVE

We developed an examination to assess internal medicine residents' knowledge of ambulatory geriatrics.

METHODS

A consensus panel developed a 30-question examination based on topics in the American Board of Internal Medicine (ABIM) Certification Examination Blueprint, the ABIM in-training examinations, and the American Geriatrics Society Goals and Objectives. Questions were reviewed, edited, and then administered to medical students, internal medicine residents, primary care providers, and geriatricians.

RESULTS

Ninety-eight individuals (20 fourth-year medical students, 57 internal medicine residents, 11 primary care faculty members, and 10 geriatrics fellowship-trained physicians) took the examination. Based on psychometric analysis of the results, 5 questions were deleted because of poor discriminatory power. The Cronbach α coefficient of the remaining 25 questions was 0.48; however, assessment of interitem consistency may not be an appropriate measure, given the variety of clinical topics on which questions were based. Scores increased with higher levels of training in geriatrics (P < .001).

CONCLUSION

Our preliminary study suggests that the examination we developed is a reasonably valid method to assess knowledge of ambulatory geriatric care and may be useful in assessing residents.

Medical ICU admissions during weekday rounds are not associated with mortality: a single-center analysis

This study investigated whether intensive care unit (ICU) admissions to the research team's tertiary care academic hospital during morning rounds was associated with increased mortality. Discharge data were analyzed on 1912 patients admitted to the ICUs between July 2007 and June 2011. Measures included discharge disposition, time of admission to the ICU, source of admission, and expected mortality score. Descriptive statistics were generated to examine the proportion of subjects who died based on admission time to the ICU, and Pearson's χ(2) test was used to test the null hypothesis that mortality rates for admissions during rounds and those at other times of the day would be similar. No difference in mortality was detected between admissions during rounds and all other times, whether analyzed using a bivariate (P = .55) or multivariable (P = .78) analysis. In this study, mortality was associated with severity of illness and not associated with admission during morning rounds.

The effect of moderate Parkinson's disease on compensatory backwards stepping

Postural instability is a major unmet need in the treatment of Parkinson's disease (PD) and its progression is not well understood. This study examined compensatory stepping taken in response to a backwards waist pull in participants with moderate PD (H&Y III) compared to age-range matched healthy controls (HC). The first step in the response was quantified in terms of strategy, temporal, kinematic, and center of pressure (COP) parameters previously observed to be significantly different in mild PD (H&Y II) compared to HC. Patients with moderate PD, compared to HC, utilized more steps to regain balance, had a longer weight-shift-time, and utilized a base-width neutral step to regain balance. However, there were no differences in ankle angle or COP location at landing as observed in mild PD, possibly due to the use of the base-width neutral step. These results suggest that moderate PD significantly impairs the compensatory response to a backwards pull. Further study should examine the progression of impairment in compensatory responses across PD severity levels, and the correlation with fall risk.

Stroke and the "stroke belt" in dialysis: contribution of patient characteristics to ischemic stroke rate and its geographic variation

Geographic variation in stroke rates is well established in the general population, with higher rates in the South than in other areas of the United States. ESRD is a potent risk factor for stroke, but whether regional variations in stroke risk exist among dialysis patients is unknown. Medicare claims from 2000 to 2005 were used to ascertain ischemic stroke events in a large cohort of 265,685 incident dialysis patients. A Poisson generalized linear mixed model was generated to determine factors associated with stroke and to ascertain state-by-state geographic variability in stroke rates by generating observed-to-expected (O/E) adjusted rate ratios for stroke. Older age, female sex, African American race and Hispanic ethnicity, unemployed status, diabetes, hypertension, history of stroke, and permanent atrial fibrillation were positively associated with ischemic stroke, whereas body mass index >30 kg/m(2) was inversely associated with stroke (P<0.001 for each). After full multivariable adjustment, the three states with O/E rate ratios >1.0 were all in the South: North Carolina, Mississippi, and Oklahoma. Regional efforts to increase primary prevention in the "stroke belt" or to better educate dialysis patients on the signs of stroke so that they may promptly seek care may improve stroke care and outcomes in dialysis patients.

Hyperbaric oxygen improves engraftment of ex-vivo expanded and gene transduced human CD34⁺ cells in a murine model of umbilical cord blood transplantation

Delayed engraftment and graft failure represent major obstacles to successful umbilical cord blood (UCB) transplantation. Herein, we evaluated the use of hyperbaric oxygen (HBO) therapy as an intervention to improve human UCB stem/progenitor cell engraftment in an immune deficient mouse model. Six- to eight-week old NSG mice were sublethally irradiated 24 hours prior to CD34⁺ UCB cell transplant. Irradiated mice were separated into a non-HBO group (where mice remained under normoxic conditions) and the HBO group (where mice received 2 hours of HBO therapy; 100% oxygen at 2.5 atmospheres absolute). Four hours after completing HBO therapy, both groups intravenously received CD34⁺ UCB cells that were transduced with a lentivirus carrying luciferase gene and expanded for in vivo imaging. Mice were imaged and then sacrificed at one of 10 times up to 4.5 months post-transplant. HBO treated mice demonstrated significantly improved bone marrow, peripheral blood, and spleen retention and subsequent engraftment. In addition, HBO significantly improved peripheral, spleen and bone marrow engraftment of human myeloid and B-cell subsets. In vivo imaging demonstrated that HBO mice had significantly higher ventral and dorsal bioluminescence values. These studies suggest that HBO treatment of NSG mice prior to UCB CD34⁺ cell infusion significantly improves engraftment.

Impact of admission blood glucose level on outcomes in community-acquired pneumonia in older adults

BACKGROUND

Community-acquired pneumonia (CAP) is a common cause of morbidity and mortality in older adults. Although diabetes mellitus is a risk factor for pneumonia, the clinical impact of blood glucose level at the time of admission is not clear. Our goal was to examine the association between admission hyperglycemia and subsequent mortality, length of stay, and readmission outcomes in older adults with CAP.

METHODS

A retrospective observational study was conducted using hospital data for community-acquired pneumonia admissions in 857 persons from January 1, 2008 to December 31, 2010. We examined the effects of admission glucose level on mortality, length of stay, and 30 day readmission, adjusted for demographic factors and comorbidity.

RESULTS

The mean age of the sample was 64 years, and 51% of the subjects were female. Inpatient mortality occurred in 4.6% and the median length of stay was 5 days (interquartile range 3-9 days). Readmission within 30 days occurred in 17%. We found little impact of first glucose measures on in-hospital mortality (P = 0.94), length of stay (P = 0.95), and 30-day readmission (P = 0.56). Subjects 65 years and older trended towards higher in-hospital mortality. Older age, cancer, heart failure, and cirrhosis were associated with adverse outcomes.

CONCLUSION

Glucose level upon admission for community-acquired pneumonia was not associated with adverse outcomes within 30 days in older adults.

Fracture risk in nursing home residents initiating antipsychotic medications

OBJECTIVES

To determine whether antipsychotic medication initiation is associated with subsequent fracture in nursing home residents, whether fracture rates differ between users of first- and second-generation antipsychotics, and whether fracture rates differ between users of haloperidol, risperidone, olanzapine, and quetiapine.

DESIGN

Time-to-event analyses were conducted in a retrospective cohort using linked Medicaid; Medicare; Minimum Data Set; and Online Survey, Certification, and Reporting data sets.

SETTING

Nursing homes in California, Florida, Missouri, New Jersey, and Pennsylvania.

PARTICIPANTS

Nursing home residents aged ≥ 65.

MEASUREMENTS

Fracture outcomes (any fracture; hip fracture) in users of first- and second-generation anti-psychotic and specifically users of haloperidol, risperidone, olanzapine, and quetiapine. Comparisons incorporated propensity scores that included individual- (demographic characteristics, comorbidity, diagnoses, weight, fall history, concomitant medications, cognitive performance, physical function, aggressive behavior) and facility- (nursing home size, ownership factors, staffing levels) level variables.

RESULTS

Of 8,262 subjects (in 4,131 pairs), 4.3% suffered any fracture during observation, with 1% having a hip fracture during an average follow-up period of 93 ± 71 days (range 1-293 days). Antipsychotic initiation was associated with any fracture (hazard ratio (HR) = 1.39, P = .004) and hip fracture (HR = 1.76, P = .02). The highest risk was found for hip fracture when antipsychotic use was adjusted for dose (HR = 2.96, P = .008), but no differences in time to fracture were found between first- and second-generation agents or between individual drugs.

CONCLUSION

Antipsychotic initiation is associated with fracture in nursing home residents, but risk does not differ between commonly used antipsychotics.

Impact of race on cumulative exposure to antihypertensive medications in dialysis

BACKGROUND

Racial minorities typically have less exposure than non-minorities to antihypertensive medications across an array of cardiovascular conditions in the general population. However, cumulative exposure has not been investigated in dialysis patients.

METHODS

In a longitudinal analysis of 38,381 hypertensive dialysis patients, prescription drug data from Medicaid was linked to Medicare data contained in United States Renal Data System core data, creating a national cohort of dialysis patients dually eligible for Medicare and Medicaid services. The proportion of days covered (PDC) was calculated to determine cumulative exposure to angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), β-blockers, and calcium-channel blockers (CCDs). The factors associated with use of these medications were modeled through weighted linear regression, with derivation of the adjusted odds ratios (AORs) for exposure.

RESULTS

Relative to non-Hispanic Caucasians, African-American, Hispanic, or Other race/ethnicity were significantly associated with less exposure to β-blockers (AOR 0.56-0.69, P < 0.001 in each case) and CCBs (AOR 0.84-0.85, P < 0.001 in each case); African-American race and Hispanic ethnicity had AORs of 0.78 and 0.73 for ACEIs and ARBs, respectively (P < 0.001 in both cases). Collectively, the odds of exposure to each class of medication for minorities was about three-quarters of that for Caucasians.

CONCLUSIONS

Given that dually Medicare-and-Medicaid-eligible dialysis patients have insurance coverage for prescription medications as well as regular contact with health care providers, differences by race in exposure to antihypertensive medications should with time be minimal among patients who are candidates for these drugs. The causes of differences by race in exposure to antihypertensive medications over the course of time should be further examined.

Atrial fibrillation and risk of stroke in dialysis patients

PURPOSE

Both stroke and chronic atrial fibrillation (AF) are common in dialysis patients, but uncertainty exists in the incidence of new strokes and the risk conferred by chronic AF.

METHODS

A cohort of dually eligible (Medicare and Medicaid) incident dialysis patients was constructed. Medicare claims were used to determine the onset of chronic AF, which was specifically treated as a time-dependent covariate. Cox proportional hazards models were used to model time to stroke.

RESULTS

Of 56,734 patients studied, 5629 (9.9%) developed chronic AF. There were 22.8 ischemic and 5.0 hemorrhagic strokes per 1000 patient-years, a ratio of approximately 4.5:1. Chronic AF was independently associated with time to ischemic (hazard ratio [HR], 1.26; 99% confidence interval [CI], 1.06-1.49; P = .0005), but not hemorrhagic, stroke. Race was strongly associated with hemorrhagic stroke: African Americans (HR, 1.46; 99% CI, 1.08-1.96), Hispanics (HR, 1.64; 99% CI, 1.16-2.31), and others (HR, 1.76; 99% CI, 1.16-2.78) had higher rates than did Caucasians (all P < .001).

CONCLUSIONS

Chronic AF has a significant, but modest, association with ischemic stroke. Race/ethnicity is strongly associated with hemorrhagic strokes. The proportion of strokes owing to hemorrhage is much higher than in the general population.

Identifying incident oral and pharyngeal cancer cases using Medicare claims

Background

Baseline and trend data for oral and pharyngeal cancer incidence is limited. A new algorithm was derived using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database to create an algorithm to identify incident cases of oral and pharyngeal cancer using Medicare claims.

Methods

Using a split-sample approach, Medicare claims’ procedure and diagnosis codes were used to generate a new algorithm to identify oral and pharyngeal cancer cases and validate its operating characteristics.

Results

The algorithm had high sensitivity (95%) and specificity (97%), which varied little by age group, sex, and race and ethnicity.

Conclusion

Examples of the utility of this algorithm and its operating characteristics include using it to derive baseline and trend estimates of oral and pharyngeal cancer incidence. Such measures could be used to provide incidence estimates where they are lacking or to serve as comparator estimates for tumor registries.

Input data quality control for NDNQI national comparative statistics and quarterly reports: a contrast of three robust scale estimators for multiple outlier detection

Background

To evaluate institutional nursing care performance in the context of national comparative statistics (benchmarks), approximately one in every three major healthcare institutions (over 1,800 hospitals) across the United States, have joined the National Database for Nursing Quality Indicators® (NDNQI®). With over 18,000 hospital units contributing data for nearly 200 quantitative measures at present, a reliable and efficient input data screening for all quantitative measures for data quality control is critical to the integrity, validity, and on-time delivery of NDNQI reports.

Methods

With Monte Carlo simulation and quantitative NDNQI indicator examples, we compared two ad-hoc methods using robust scale estimators, Inter Quartile Range (IQR) and Median Absolute Deviation from the Median (MAD), to the classic, theoretically-based Minimum Covariance Determinant (FAST-MCD) approach, for initial univariate outlier detection.

Results

While the theoretically based FAST-MCD used in one dimension can be sensitive and is better suited for identifying groups of outliers because of its high breakdown point, the ad-hoc IQR and MAD approaches are fast, easy to implement, and could be more robust and efficient, depending on the distributional property of the underlying measure of interest.

Conclusion

With highly skewed distributions for most NDNQI indicators within a short data screen window, the FAST-MCD approach, when used in one dimensional raw data setting, could overestimate the false alarm rates for potential outliers than the IQR and MAD with the same pre-set of critical value, thus, overburden data quality control at both the data entry and administrative ends in our setting.

Simultaneous evaluation of abstinence and relapse using a Markov chain model in smokers enrolled in a two-year randomized trial

BACKGROUND

GEE and mixed models are powerful tools to compare treatment effects in longitudinal smoking cessation trials. However, they are not capable of assessing the relapse (from abstinent back to smoking) simultaneously with cessation, which can be studied by transition models.

METHODS

We apply a first-order Markov chain model to analyze the transition of smoking status measured every 6 months in a 2-year randomized smoking cessation trial, and to identify what factors are associated with the transition from smoking to abstinent and from abstinent to smoking. Missing values due to non-response are assumed non-ignorable and handled by the selection modeling approach.

RESULTS

Smokers receiving high-intensity disease management (HDM), of male gender, lower daily cigarette consumption, higher motivation and confidence to quit, and having serious attempts to quit were more likely to become abstinent (OR = 1.48, 1.66, 1.03, 1.15, 1.09 and 1.34, respectively) in the next 6 months. Among those who were abstinent, lower income and stronger nicotine dependence (OR = 1.72 for ≤ vs. > 40 K and OR = 1.75 for first cigarette ≤ vs. > 5 min) were more likely to have relapse in the next 6 months.

CONCLUSIONS

Markov chain models allow investigation of dynamic smoking-abstinence behavior and suggest that relapse is influenced by different factors than cessation. The knowledge of treatments and covariates in transitions in both directions may provide guidance for designing more effective interventions on smoking cessation and relapse prevention.

Association of race with cumulative exposure to statins in dialysis

BACKGROUND

Patients on dialysis have high rates of cardiovascular disease and are frequently treated with HMG-CoA reductase inhibitors. Given that these patients have insurance coverage for medications as well as regular contact with health care providers, differences by race in exposure to statins over time should be minimal among patients who are candidates for the drug.

METHODS

We created a cohort of incident dialysis patients who were dually eligible for Medicare and Medicaid services. We determined the proportion of days covered (or PDC, a marker of cumulative medication exposure) by a statin prescription over a mean of 2.0 ± 1.4 years. Ordinary least squares regression was used to determine the factors associated with cumulative drug exposure.

RESULTS

Of the 18,727 patients who filled at least one prescription for a statin, mean PDC was 0.57 ± 0.32. The unadjusted PDC was higher for Caucasians (0.63 ± 0.31) than for African-Americans (0.51 ± 0.32), Hispanics (0.54 ± 0.31), and individuals of other race/ethnicity (0.58 ± 0.32). In multivariable modeling, Caucasian race was independently associated with greater exposure to statins. Relative to Caucasians, the adjusted odds ratios for the PDC for African-Americans was 0.47 (95% confidence interval, CI, 0.43-0.50), for Hispanics 0.52 (0.48-0.56) and for others, 0.72 (0.64-0.81).

CONCLUSIONS

Despite insurance coverage, regular contact with health care providers, and at least one prescription for a statin, there are large differences by race in statin exposure over time. The provider- and patient-associated factors related to this phenomenon should be further examined.

The Box-Cox power transformation on nursing sensitive indicators: does it matter if structural effects are omitted during the estimation of the transformation parameter?

Background

Many nursing and health related research studies have continuous outcome measures that are inherently non-normal in distribution. The Box-Cox transformation provides a powerful tool for developing a parsimonious model for data representation and interpretation when the distribution of the dependent variable, or outcome measure, of interest deviates from the normal distribution. The objectives of this study was to contrast the effect of obtaining the Box-Cox power transformation parameter and subsequent analysis of variance with or without a priori knowledge of predictor variables under the classic linear or linear mixed model settings.

Methods

Simulation data from a 3 × 4 factorial treatments design, along with the Patient Falls and Patient Injury Falls from the National Database of Nursing Quality Indicators (NDNQI^®) for the 3^rd quarter of 2007 from a convenience sample of over one thousand US hospitals were analyzed. The effect of the nonlinear monotonic transformation was contrasted in two ways: a) estimating the transformation parameter along with factors with potential structural effects, and b) estimating the transformation parameter first and then conducting analysis of variance for the structural effect.

Results

Linear model ANOVA with Monte Carlo simulation and mixed models with correlated error terms with NDNQI examples showed no substantial differences on statistical tests for structural effects if the factors with structural effects were omitted during the estimation of the transformation parameter.

Conclusions

The Box-Cox power transformation can still be an effective tool for validating statistical inferences with large observational, cross-sectional, and hierarchical or repeated measure studies under the linear or the mixed model settings without prior knowledge of all the factors with potential structural effects.

Effects of premature birth on the risk for alcoholism appear to be greater in males than females

OBJECTIVE

A large Danish birth cohort was used to test the independent and joint effects of perinatal measures associated with premature birth as predictors of the development of alcoholism in male and female subjects.

METHOD

Subjects were born at the Copenhagen University Hospital between 1959 and 1961 (N = 9,125). A comprehensive series of measures was obtained for each of the 8,109 surviving and eligible infants before birth, during birth, shortly after birth, and at 1 year. The adult alcoholism outcome was defined as any ICD-10 F10 diagnosis (Mental and behavioral disorders due to alcohol use) or an equivalent ICD-8 diagnosis found in the Danish Psychiatric Central Research Register or the Municipal Alcohol Clinics of Copenhagen by 2007.

RESULTS

Multiple perinatal markers of premature birth independently predicted the development of an alcoholism diagnosis in male (n = 310) but not female (n = 138) subjects. Logistic regression modeling with a global prematurity score, adjusted for social status, maternal smoking, and gender, indicated a significant association of prematurity score for males (p < .02), but not females (p = .51), on the risk of developing an alcohol use disorder.

CONCLUSIONS

The results suggest that neurodevelopmental sequelae of premature birth are associated with gender-specific effects on the development of alcoholism in the male baby: small, premature, or growth-delayed male babies appear to be selectively vulnerable to alcoholic drinking years later. The findings implicate neurodevelopmental influences in alcoholism pathophysiology in males and suggest the possibility of distinct, gender-specific pathways in the etiology of severe problem drinking.

Geographic variation in cardioprotective antihypertensive medication usage in dialysis patients

BACKGROUND

Despite their high risk of adverse cardiac outcomes, persons on long-term dialysis therapy have had lower use of antihypertensive medications with cardioprotective properties, such as angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers (ARBs), β-blockers, and calcium channel blockers, than might be expected. We constructed a novel database that permits detailed exploration into the demographic, clinical, and geographic factors associated with the use of these agents in hypertensive long-term dialysis patients.

STUDY DESIGN

National cross-sectional retrospective analysis linking Medicaid prescription drug claims with US Renal Data System core data.

SETTING & PARTICIPANTS

48,882 hypertensive long-term dialysis patients who were dually eligible for Medicaid and Medicare services in 2005.

FACTORS

Demographics, comorbid conditions, functional status, and state of residence.

OUTCOMES

Prevalence of cardioprotective antihypertensive agents in Medicaid pharmacy claims and state-specific observed to expected ORs of medication exposure.

MEASUREMENTS

Factors associated with medication use were modeled using multilevel logistic regression models.

RESULTS

In multivariable analyses, cardioprotective antihypertensive medication exposure was associated significantly with younger age, female sex, nonwhite race, intact functional status, and use of in-center hemodialysis. Diabetes was associated with a statistically significant 28% higher odds of ACE-inhibitor/ARB use, but congestive heart failure was associated with only a 9% increase in the odds of β-blocker use and no increase in ACE-inhibitor/ARB use. There was substantial state-by-state variation in the use of all classes of agents, with a greater than 2.9-fold difference in adjusted-rate ORs between the highest and lowest prescribing states for ACE inhibitors/ARBs and a 3.6-fold difference for β-blockers.

LIMITATIONS

Limited generalizability beyond study population.

CONCLUSIONS

In publicly insured long-term dialysis patients with hypertension, there were marked differences in use rates by state, potentially due in part to differences in Medicaid benefits. However, geographic characteristics also were associated with exposure, suggesting clinical uncertainty about the utility of these medications.

Elevated FGF23 levels are associated with impaired calcium-mediated suppression of PTH in ESRD

CONTEXT

The positive association of elevated fibroblast growth factor-23 (FGF23) with PTH levels in the setting of secondary hyperparathyroidism is paradoxical to the purported effects of FGF23 to suppress PTH secretion.

OBJECTIVE

We used dynamic calcium-mediated suppression of PTH levels in hemodialysis (HD) patients to determine the relationship between FGF23 levels and parathyroid gland function.

DESIGN

HD patients with elevated PTH were washed out of vitamin D analogs and/or calcimimetics and then exposed them to a high-calcium dialysate bath designed to suppress PTH.

SETTING

The study was conducted at an outpatient HD unit of an academic medical center.

PARTICIPANTS

Eighteen maintenance HD patients with elevated PTH levels participated in the study.

MAIN OUTCOME MEASURES

Ionized calcium (iCa), PTH, and FGF23 levels were measured during HD. The slope of the relationship between iCa and PTH (a marker of parathyroid gland mass) and the iCa level required for a 50% reduction in PTH were determined, and the association of these with FGF23 levels was determined.

RESULTS

Increased baseline log FGF23 levels were associated with putative alterations in gland mass as estimated by significantly shallower slopes of the iCa/PTH suppression curves (P = 0.0004), but there was no association between FGF23 and calcium sensing as measured by ionized Ca associated with a 50% suppression of PTH (P = 0.38). FGF23 levels decreased significantly during HD, but this change was not correlated with decrements in either renal phosphate or PTH.

CONCLUSIONS

High FGF23 levels may be a marker for parathyroid gland hyperplasia in HD patients. Acute reductions in neither PTH nor renal phosphate during dialysis correlated with PTH suppression.

Elevated FGF23 Levels Are Associated with Impaired Calcium-Mediated Suppression of PTH in ESRD

Context: The positive association of elevated fibroblast growth factor-23 (FGF23) with PTH levels in the setting of secondary hyperparathyroidism is paradoxical to the purported effects of FGF23 to suppress PTH secretion.

Objective: We used dynamic calcium-mediated suppression of PTH levels in hemodialysis (HD) patients to determine the relationship between FGF23 levels and parathyroid gland function.

Design: HD patients with elevated PTH were washed out of vitamin D analogs and/or calcimimetics and then exposed them to a high-calcium dialysate bath designed to suppress PTH.

Setting: The study was conducted at an outpatient HD unit of an academic medical center.

Participants: Eighteen maintenance HD patients with elevated PTH levels participated in the study.

Main Outcome Measures: Ionized calcium (iCa), PTH, and FGF23 levels were measured during HD. The slope of the relationship between iCa and PTH (a marker of parathyroid gland mass) and the iCa level required for a 50% reduction in PTH were determined, and the association of these with FGF23 levels was determined.

Results: Increased baseline log FGF23 levels were associated with putative alterations in gland mass as estimated by significantly shallower slopes of the iCa/PTH suppression curves (P = 0.0004), but there was no association between FGF23 and calcium sensing as measured by ionized Ca associated with a 50% suppression of PTH (P = 0.38). FGF23 levels decreased significantly during HD, but this change was not correlated with decrements in either renal phosphate or PTH.

Conclusions: High FGF23 levels may be a marker for parathyroid gland hyperplasia in HD patients. Acute reductions in neither PTH nor renal phosphate during dialysis correlated with PTH suppression.

Power for studies with random group sizes

In any study it is essential to select the sample size carefully to ensure adequate power. For many studies this is simple: recruit a desired number of subjects within each group, conduct measurements, and perform the statistical test. In some studies (e.g. observational studies), however, the group membership is unknown at recruitment. In this paper we examine the effect of random group sizes on power. Additionally, we consider the situation when the group proportions are unknown and specified by a prior distribution. The problem that initially motivated this research is presented (power for a 2-by-2 table), as are examples using continuous outcomes. We find that standard estimates of power using expected group sizes can over or underestimate power. SAS macros are available at http://www.phs.wfubmc.edu/public/wambrosi/RandomPower.

Optimal designs for two-arm, phase II clinical trial design with multiple constraints

Multi-stage Phase II trials are often employed in practice but may not be the best approach when the endpoint of interest is not obtained soon after enrollment and/or when a control arm is desired. We present a new design in which sample size determination includes a control arm and allows for the estimation of response for each treatment as well as estimation of the difference in the response rates. We evaluate this design under varying allocation schemes to treatment arms and response rates for each treatment.

Validation of the support provided measure among spouses of smokers receiving a clinical smoking cessation intervention

Studies indicate a positive association between social support and smoking cessation. However, clinic-based interventions designed to increase social support have had limited success. Most studies have relied on only the smoker's perceptions of support received while few have assessed the support provider's report of support delivered. Understanding supportive interactions between support providers and recipients may assist in developing effective support interventions for cessation. The current investigation examined the perceptions of smoking-specific support provided by the spouse of a partner who smokes and was seen for a nicotine dependence consultation. Specifically, we examined spouse reported willingness to help their spouse quit, interest in learning ways to help their spouse quit, and characteristics associated with the provision of smoking-specific supportive behaviors (as assessed via the Support Provided Measure, SPM), in the 2-weeks prior to the consultation. The current investigation also examined the concurrent validity of the SPM with a validated measure of support provided to a smoker, the Partner Interaction Questionnaire (PIQ), accounting for social desirability bias and smoker readiness to change. The sample comprised 84 adult cigarette smokers seen for a clinical smoking cessation intervention and their spouses (N = 84). Results indicate that a high percentage of spouses are willing to help their partner who smokes and interested in learning way to help. As expected, spouses who were females and had never smoked had higher scores on the SPM than males or current smokers. The SPM was significantly correlated with the PIQ positive (r = 0.50, p < 0.01) and negative (r = 0.44, p <0.01) item scales overall and for spouses whose partners reported higher levels of readiness to quit smoking (r = 0.54, p < 0.01; r = 0.50, p < 0.01, respectively). Suggestions for future research are offered.

Considering health insurance: how do dialysis initiates with Medicaid coverage differ from persons without Medicaid coverage?

BACKGROUND

Type of health insurance is an important mediator of medical outcomes in the United States. Medicaid, a jointly sponsored Federal/State programme, is designed to serve medically needy individuals. How these patients differ from non-Medicaid-enrolled incident dialysis patients and how these differences have changed over time have not been systematically examined.

METHODS

Using data from the United States Renal Data System, we identified individuals initiating dialysis from 1995 to 2004 and categorized their health insurance status. Longitudinal trends in demographic, risk behaviour, functional, comorbidity, laboratory and dialysis modality factors, as reported on the Medical Evidence Form (CMS-2728), were examined in all insurance groups. Polychotomous logistic regression was used to estimate adjusted generalized ratios (AGRs) for these factors by insurance status, with Medicaid as the referent insurance group.

RESULTS

Overall, males constitute a growing percentage of both Medicaid and non-Medicaid patients, but in contrast to other insurance groups, Medicaid has a higher proportion of females. Non-Caucasians also constitute a higher proportion of Medicaid patients than non-Medicaid patients. Body mass index increased in all groups over time, and all groups witnessed a significant decrease in initiation on peritoneal dialysis. Polychotomous regression showed generally lower AGRs for minorities, risk behaviours and functional status, and higher AGRs for males, employment and self-care dialysis, for non-Medicaid insurance relative to Medicaid.

CONCLUSIONS

While many broad parallel trends are evident in both Medicaid and non-Medicaid incident dialysis patients, many important differences between these groups exist. These findings could have important implications for policy planners, providers and payers.

Early biomechanical markers of postural instability in Parkinson's disease

Current clinical assessments do not adequately detect the onset of postural instability in the early stages of Parkinson's disease (PD). The aim of this study was to identify biomechanical variables that are sensitive to the effects of early Parkinson's disease on the ability to recovery from a balance disturbance. Ten adults diagnosed with idiopathic PD and no clinically detectable postural instability, and ten healthy age-range matched controls (HC) completed the study. The first step in the response to a backwards waist pull was quantified in terms of strategy, temporal, kinematic, kinetic, and center of pressure (COP) variables. People with PD, compared to HC, tended to be less consistent in the choice of stepping limb, utilized more time for weight shift, used a modified ankle joint motion prior to liftoff, and the COP was further posterior at landing. The study results demonstrate that PD changes the response to a balance disturbance which can be quantified using biomechanical variables even before the presence of clinically detectable postural instability. Further studies are required to determine if these variables are sensitive and specific to postural instability.