Clinical and economic outcomes in an observational study of COPD maintenance therapies: multivariable regression versus propensity score matching

Melissa H Roberts1, Anand A Dalal21Lovelace Clinic Foundation, (Lovelace Respiratory Research Institute at the time of the study), Albuquerque, NM, 2US Health Outcomes, GlaxoSmithKline, Durham, NC, USAPurpose: To investigate equivalency of results from multivariable regression (MR) and propensity score matching (PSM) models, observational research methods used to mitigate bias stemming from non-randomization (and consequently unbalanced groups at baseline), using, as an example, a large study of chronic obstructive pulmonary disease (COPD) initial maintenance therapy.Methods: Patients were 32,338 health plan members, age ≥40 years, with COPD initially treated with fluticasone propionate/salmeterol combination (FSC), tiotropium (TIO), or ipratropium (IPR) alone or in combination with albuterol. Using MR and PSM methods, the proportion of patients with COPD-related health care utilization, mean costs, odds ratios (ORs), and incidence rate ratios (IRRs) for utilization events were calculated for the 12 months following therapy initiation.Results: Of 12,595 FSC, 9126 TIO, and 10,617 IPR patients meeting MR inclusion criteria, 89.1% (8135) of TIO and 80.2% (8514) of IPR patients were matched to FSC patients for the PSM analysis. Methods produced substantially similar findings for mean cost comparisons, ORs, and IRRs for most utilization events. In contrast to MR, for TIO compared to FSC, PSM did not produce statistically significant ORs for hospitalization or outpatient visit with antibiotic or significant IRRs for hospitalization or outpatient visit with oral corticosteroid. As in the MR analysis, compared to FSC, ORs and IRRs for all other utilization events, as well as mean costs, were less favorable for IPR and TIO.Conclusion: In this example of an observational study of maintenance therapy for COPD, more than 80% of the original treatment groups used in the MR analysis were matched to comparison treatment groups for the PSM analysis. While some sample size was lost in the PSM analysis, results from both methods were similar in direction and statistical significance, suggesting that MR and PSM were equivalent methods for mitigating bias.Keywords: multivariate analysis, outcomes research, propensity score, pulmonary disease, chronic obstructive, statistical bias, statistical model

Testing single aliquot regenerative dose (SAR) protocols for violet stimulated luminescence

Basic assumptions of the single aliquot regenerative dose (SAR) protocol are tested using the violet stimulated luminescence (VSL) signal from quartz. The VSL signal is shown to be reduced to a sufficiently low background level between SAR steps, and the SAR protocol appears to adequately correct for sensitivity changes during measurement. The VSL SAR protocol can recover a large (405 Gy) laboratory beta dose within uncertainties, however the mean value for the dose recovery ratio is commonly 0.8 or less. This poor behaviour is echoed in the measurements of equivalent dose (De) for a sample with an expected De of ∼354 Gy, which underestimates De by 50–70%. Further investigations are required to understand the mechanisms underlying these underestimations in VSL SAR De values

Economic burden of chronic bronchitis in the United States: a retrospective case-control study

Christopher M Blanchette1, Melissa H Roberts1, Hans Petersen1, Anand A Dalal2, Douglas W Mapel31Division of Clinical and Outcomes Research, Lovelace Respiratory Research Institute, Kannapolis, NC, USA; 2US Health Outcomes, GlaxoSmithKline, Research Triangle Park, NC, USA; 3Lovelace Clinic Foundation, Albuquerque, NM, USABackground: Chronic bronchitis (CB) is often misdiagnosed or diagnosed at a later stage of chronic obstructive pulmonary disease (COPD). We examined how this later diagnosis may impact health care costs and utilization during the 12 months prior to and 24 months post initial CB diagnosis.Methods: This retrospective case-control analysis used claims data from a large US database from July 1, 2003 through June 30, 2007. Patients with CB aged 40 years and older were propensity matched (N = 11,674) to patients without evidence of COPD or asthma by demographics, CB diagnosis quarter/year, and comorbidities. Group differences were assessed using Student's t-test and Pearson chi-square test statistics.Results: Six months prediagnosis, CB patients had higher frequencies of any hospitalization (9.6%, 6.7%; P < 0.05), emergency department/urgent care visits (13.3%, 6.7%; P < 0.05), and prescriptions (97.3%, 94.1%; P < 0.05). Six months postdiagnosis, CB patients had 5.6 times more hospitalizations (P < 0.05) and 3.1 times more emergency department/urgent care visits (P < 0.05) compared with controls. Mean total costs (US) for CB patients 12 months prediagnosis were significantly higher than controls (months 12–7: 4212, 3826; P < 0.05; months 6–1: 5289, 4285; P < 0.05). CB patients had higher mean total costs (8919; P < 0.05) 6 months postdiagnosis. Costs remained $2429 higher for CB patients 19–24 months postdiagnosis (P < 0.05).Conclusion: Health care costs and utilization among CB patients are increased both prior to diagnosis and during the 2 years postdiagnosis. This study suggests that not accurately diagnosing CB early has a substantial impact on health care costs, and that the economic burden for CB patients remains elevated even after adjustment for comorbidities associated with COPD.Keywords: chronic bronchitis, burden, economic, chronic obstructive pulmonary diseas

In vivo microdialysis to determine subcutaneous interstitial fluid penetration and pharmacokinetics of fluconazole in intensive care unit patients with sepsis

The objective of the study was to describe the subcutaneous interstitial fluid (ISF) pharmacokinetics of fluconazole in critically ill patients with sepsis. This prospective observational study was conducted at two tertiary intensive care units in Australia. Serial fluconazole concentrations were measured over 24 h in plasma and subcutaneous ISF using microdialysis. The concentrations in plasma and microdialysate were measured using a validated high-performance liquid chromatography system with electrospray mass spectrometer detector method. Noncompartmental pharmacokinetic analysis was performed. Twelve critically ill patients with sepsis were enrolled. The mean in vivo fluconazole recovery rates +/- standard deviation (SD) for microdialysis were 51.4% +/- 16.1% with a mean (+/- SD) fluconazole ISF penetration ratio of 0.52 +/- 0.30 (coefficient of variation, 58%). The median free plasma area under the concentration-time curve from 0 to 24 h (AUC(0-24)) was significantly higher than the median ISF AUC(0-24) (340.4 versus 141.1 mg . h/liter; P = 0.004). There was no statistical difference in median fluconazole ISF penetration between patients receiving and not receiving vasopressors (median, 0.28 versus 0.78; P = 0.106). Both minimum and the maximum concentrations of drug in serum (C-max and C-min) showed a significant correlation with the fluconazole plasma exposure (Cmax, R-2 = 0.86, P < 0.0001; Cmin, R-2 = 0.75, P < 0.001). Our data suggest that fluconazole was distributed variably, but incompletely, from plasma into subcutaneous interstitial fluid in this cohort of critically ill patients with sepsis. Given the variability of fluconazole interstitial fluid exposures and lack of clinically identifiable factors by which to recognize patients with reduced distribution/exposure, we suggest higher than standard doses to ensure that drug exposure is adequate at the site of infection

Effect of obesity on the population pharmacokinetics of meropenem in critically ill patients

Severe pathophysiological changes in critical illness can lead to dramatically altered antimicrobial pharmacokinetics (PK). The additional effect of obesity on PK potentially increases the challenge for effective dosing. The aim of this prospective study was to describe the population PK of meropenem for a cohort of critically ill patients, including obese and morbidly obese patients. Critically ill patients prescribed meropenem were recruited into the following three body mass index (BMI) groups: nonobese (18.5 to 29.9 kg/m(2)), obese (30.0 to 39.9 kg/m(2)), and morbidly obese (>= 40 kg/m(2)). Serial plasma samples were taken, and meropenem concentrations were determined using a validated chromatographic method. Population PK analysis and Monte Carlo dosing simulations were undertaken with Pmetrics. Nineteen critically ill patients with different BMI categories were enrolled. The patients' mean +/- standard deviation (SD) age, weight, and BMI were 49 +/- 15.9 years, 95 +/- 22.0 kg, and 33 +/- 7.0 kg/m(2), respectively. A two-compartment model described the data adequately. The mean +/- SD parameter estimates for the final covariate model were as follows: clearance (CL), 15.5 +/- 6.0 liters/h; volume of distribution in the central compartment (V-1), 11.7 +/- 5.8 liters; intercompartmental clearance from the central compartment to the peripheral compartment, 25.6 +/- 35.1 liters h(-1); and intercompartmental clearance from the peripheral compartment to the central compartment, 8.32 +/- 12.24 liters h(-1). Higher creatinine clearance (CLCR) was associated with a lower probability of target attainment, with BMI having little effect. Although obesity was found to be associated with an increased V-1, dose adjustment based on CLCR appears to be more important than patient BMI

Pregnancy Induces Persistent Changes that Potentiate Apoptotic Signaling and Responses to DNA Damage

A full-term pregnancy reduces the lifetime risk of breast cancer by up to 50%. This effect is mediated, in part, by p53-dependent pathways. Gene expression profiling was used to investigate the mechanisms that alter apoptotic responses to DNA damage in the mammary gland. Radiation-induced responses in BALB/c-Trp53+/+ and BALB/c-Trp53-/- mice identified 121 genes that were altered by radiation and p53 status (p53-IR). To determine the effect of parity, mice were mated, force-weaned and mammary glands were allowed to involute for 21 days (parous) and compared with age-matched nulliparous mice. Gene expression profiles were determined in mammary tissues from nulliparous (N), parous (P), irradiated nulliparous (N-IR) and irradiated parous (P-IR) mice. The p53-IR gene signature did not differ among the N-IR and P-IR groups indicating that transcriptional activity of p53 was not altered by parity. However, expression profiles of apoptosis-related genes differed significantly in the parous group. The alterations in parous mammary tissues was accompanied by over-representation of biological processes that included “signal transduction” (e=1.69E-05). Within this set, Wnt signaling was especially pronounced (e Parity-regulated genes collaborate with p53-dependent targets, which act as a “switch”, to elicit apoptosis following ionizing radiation. The epigenetic states of the parity-regulated genes Tgfb2 and Wnt5a provide a mechanism for the persistent alterations in gene expression and apoptosis in parous mammary epithelial cells

Racial Variation in the Uptake of Onco type DX Testing for Early-Stage Breast Cancer

Oncotype DX (ODX) is a tumor gene-profiling test that aids in adjuvant chemotherapy decision-making. ODX has the potential to improve quality of care; however, if not equally accessible across racial groups, disparities in cancer care quality may persist or worsen. We examined racial disparities in ODX testing uptake