Caliper Width Research Articles

Comparison of Additional Versus No Additional Heparin During Therapeutic Oral Anticoagulation in Patients Undergoing Percutaneous Coronary Intervention

Uninterrupted oral anticoagulation (OAC) therapy can be the preferred strategy in patients with atrial fibrillation at moderate to high risk of thromboembolism undergoing percutaneous coronary intervention (PCI). To evaluate the need for additional heparins in addition to therapeutic peri-PCI OAC, we assessed bleeding complications and major adverse cardiac and cerebrovascular events in 414 consecutive patients undergoing PCI during therapeutic (international normalized ratio 2 to 3.5) periprocedural OAC. Patients were divided into those with no (n = 196) and with (n = 218) additional use of periprocedural heparins. No differences in major adverse cardiac and cerebrovascular events (4.1% vs 3.2%, p = 0.79) or major bleeding (1.0% vs 3.7%, p = 0.11) were detected, but access site complications (5.1% vs 11.0%, p = 0.032) were less frequent in those without additional heparins. When adjusted for propensity score, patients with additional heparins had a higher risk of access site complications (odds ratio 2.6, 95% confidence interval 1.1 to 6.1, p = 0.022) without any increased risk of any other adverse event. Analysis of 1-to-1 propensity-matched pairs showed a significantly higher risk of access site complication in patients receiving additional AC (13.1% vs 5.7%, p = 0.049). In conclusion, therapeutic warfarin treatment seems to provide sufficient AC for PCI. Additional heparins are not needed and may increase access site complications.

Optimal caliper widths for propensity‐score matching when estimating differences in means and differences in proportions in observational studies

In a study comparing the effects of two treatments, the propensity score is the probability of assignment to one treatment conditional on a subject's measured baseline covariates. Propensity-score matching is increasingly being used to estimate the effects of exposures using observational data. In the most common implementation of propensity-score matching, pairs of treated and untreated subjects are formed whose propensity scores differ by at most a pre-specified amount (the caliper width). There has been a little research into the optimal caliper width. We conducted an extensive series of Monte Carlo simulations to determine the optimal caliper width for estimating differences in means (for continuous outcomes) and risk differences (for binary outcomes). When estimating differences in means or risk differences, we recommend that researchers match on the logit of the propensity score using calipers of width equal to 0.2 of the standard deviation of the logit of the propensity score. When at least some of the covariates were continuous, then either this value, or one close to it, minimized the mean square error of the resultant estimated treatment effect. It also eliminated at least 98% of the bias in the crude estimator, and it resulted in confidence intervals with approximately the correct coverage rates. Furthermore, the empirical type I error rate was approximately correct. When all of the covariates were binary, then the choice of caliper width had a much smaller impact on the performance of estimation of risk differences and differences in means. Copyright © 2010 John Wiley & Sons, Ltd.

Retrospective Monocentric Study of Patients with Refractory Hodgkin Lymphoma: Allogeneic Stem Cell Transplantation (alloSCT) Compared to Conventional Treatment Using the Propensity Score Matching Method.

Abstract 3372Poster Board III-260 Background:Although Hodgkin lymphoma is usually characterized by a high chemosensitivity and a good prognosis, a minority of patients with primary refractory disease or early relapse after intensive chemotherapy presents poor outcome (Brice. British Journal of Haematology 2008 ; 141 : 3-13. Moskowitz. British Journal of Haematology 2009 ; 146 : 158-163). AlloSCT is one of the treatment-options that can be proposed for these progressive patients but the optimal management remains controversial because comparative studies are lacking. However, several groups report encouraging survival results with acceptable non relapse mortality after alloSCT with reduced intensity conditioning. Method:We retrospectively studied 31 patients who received an alloSCT in Saint-Louis Hospital, Paris. The aim of the study was to compare their outcome with those of patients with similar characteristics who did not receive alloSCT. In order to have an homogenous group of patients, we only compared patients who relapsed after an autologous SCT (autoSCT) and were alive at least 12 months after autoSCT. To correct the recruitment bias, the propensity score (PS) methodology was used to determine the probability of receiving alloSCT in the group of patients who relapsed after autoSCT, according to a set of baseline characteristics (Rosenbaum. Biometrika 1983;70:41-55). Parameters used for this PS score were age, primary chemorefractory disease and stage III-IV at first relapse. This PS was estimated using logistic regression and used to match 1:1 patients with similar propensity to receive alloSCT, based on the nearest neighbor matching using calipers of width 0.2.AlloSCT recipients characteristics: Thirty-one patients (19 males and 12 females) received an alloSCT between 2000 and 2007. Median age at alloSCT was 26 years. Median number of previous lines of chemotherapy was 3.6 (range from 2 to 7) and 28 (90%) patients were previously autografted. 13 (42%) were considered refractory to primary treatment and 11 (35%) to secondary treatment. Status at alloSCT were: 20 (65%) patients in CR, 9 (29%) in PR and 2 (6%) in progressive disease. Pre-transplant co-morbidity score was 0 in 26 (84%), 1 in 3 (10%) and 2 in 2 (6%) patients. 26 (84%) patients received a reduced intensity conditioning regimen and TBI was performed in 23 (74%) recipients. Most of the patients (n=24, 77%) received peripheral stem cells and donors were HLA-identical siblings in 15 (48%) cases. Median follow-up after autoSCT and alloSCT was 62 and 51 months respectively. All patients engrafted. Grade II-IV acute GVHD occurred in 10 (32%) patients. Chronic GVHD occurred in 13 (42%). Three months after alloSCT, 19 patients were in remission, 5 presented stable disease and 7 were progressive. Eleven patients relapsed despite alloSCT and 11 patients died. The estimated 3-year overall and event free survival were respectively 69% (95% CI [48;82]) and 41% (95% CI [23;58]) and 3-year non relapse mortality was 21% (95% CI [13;29]). Causes of death after alloSCT were: progression in 6 (55%) and toxicity in 5 (45%) patients.From the 31 alloSCT recipients, 15 matched pairs were successfully constituted according to the PS. As expected, the distribution of age (p=0.97), stage III or IV at relapse (p=0.67) and primary chemorefractory disease (p=1) were not different between patients treated by alloSCT and untreated subjects. Based on these matched pairs, the estimated hazard ratio of death was 0.24 (95% CI [0.07;0.80]) for allografted patients compared with non allografted.In conclusion, alloSCT in poor-prognosis Hodgkin lymphoma gives promising survival outcomes although performed in advanced disease and provides survival benefit with acceptable non relapse mortality in comparison with non allograft treatment as suggested by PS method. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

The concept of the marginally matched subject in propensity‐score matched analyses

Propensity-score matching is increasingly being used to reduce the impact of treatment-selection bias when estimating causal treatment effects using observational data. Matching on the propensity score creates sets of treated and untreated subjects who have a similar distribution of baseline covariates. Propensity-score matching frequently relies upon calipers, such that matched treated and untreated subjects must have propensity scores that lie within a specified caliper distance of each other. We define the 'marginally matched' subject as a subject who would be matched using the specified caliper width, but who would not have been matched had calipers with a narrower width been employed. Using patients hospitalized with an acute myocardial infarction (or heart attack) and with exposure to a statin prescription at discharge, we demonstrate that the inclusion of marginally matched subjects can have both a quantitative and qualitative impact upon the estimated treatment effect. Furthermore, marginally matched treated subjects can differ from marginally matched untreated subjects to a substantially greater degree than the differences between non-marginally matched treated and untreated subjects in the propensity-score matched sample. The concept of the marginally matched subject can be used as a sensitivity analysis to examine the impact of the matching method on the estimates of treatment effectiveness.

Antisignal recognition particle-positive polymyositis successfully treated with myeloablative autologous stem cell transplantation

<h3>Objective</h3> To evaluate disease-free survival of cervical conization prior to radical hysterectomy in patients with stage IB1 cervical cancer (International Federation of Gynecology and Obstetrics (FIGO) 2009). <h3>Methods</h3> A multicenter...

Some Methods of Propensity‐Score Matching had Superior Performance to Others: Results of an Empirical Investigation and Monte Carlo simulations

Propensity-score matching is increasingly being used to reduce the impact of treatment-selection bias when estimating causal treatment effects using observational data. Several propensity-score matching methods are currently employed in the medical literature: matching on the logit of the propensity score using calipers of width either 0.2 or 0.6 of the standard deviation of the logit of the propensity score; matching on the propensity score using calipers of 0.005, 0.01, 0.02, 0.03, and 0.1; and 5 --> 1 digit matching on the propensity score. We conducted empirical investigations and Monte Carlo simulations to investigate the relative performance of these competing methods. Using a large sample of patients hospitalized with a heart attack and with exposure being receipt of a statin prescription at hospital discharge, we found that the 8 different methods produced propensity-score matched samples in which qualitatively equivalent balance in measured baseline variables was achieved between treated and untreated subjects. Seven of the 8 propensity-score matched samples resulted in qualitatively similar estimates of the reduction in mortality due to statin exposure. 5 --> 1 digit matching resulted in a qualitatively different estimate of relative risk reduction compared to the other 7 methods. Using Monte Carlo simulations, we found that matching using calipers of width of 0.2 of the standard deviation of the logit of the propensity score and the use of calipers of width 0.02 and 0.03 tended to have superior performance for estimating treatment effects.

Mean width and caliper characteristics of network polyhedra

The kinetic modelling of space-filling grain networks has been approached traditionally by representing the grains as spheres of equivalent volume. A spherical approximation used to describe polyhedral grains, unfortunately, relinquishes most geometrical and all topological details of the grain structure. Techniques developed by Hilgenfeldt et al., and by Glicksman, describe network structures comprised of space-filling irregular polyhedra and their kinetics with regular polyhedra, which act as ‘proxies’ that preserve both local topology and network constraints. Analytical formulas based on regular polyhedra and Surface Evolver simulations are used in this study to calculate the average caliper width and mean width for extended sets of polyhedra that vary systematically from convex to concave objects. Of importance, caliper width and mean width measures allow estimation of the growth rates of grains. Comparison of these calculations and simulations, however, reveal a weak dependence between average caliper width and mean width measures and the detailed shapes of polyhedra, especially their face curvatures. This finding might, in fact, affect the application and use of linear measures as kinetic tools in quantitative microstructure measurements.

Use of the Propensity Score Matching Method to Reduce Recruitment Bias in Observational Studies: Application to the Estimation of Survival Benefit of Non-Myeloablative Allogeneic Transplantation In Patients with Multiple Myeloma Relapsing after a First Autologous Transplantation.

Despite recent advances in the treatment including Autologous Stem Cell Transplantation (A-PBSCT) and new drugs, Multiple Myeloma (MM) is still an incurable disease and the outcome of relapsing patients is still extremely grim. The use of conventional allogeneic hematopoietic SCT is limited by a high transplantation-related mortality (TRM). Allografting with nonmyeloablative conditioning (NMA-C) has therefore been considered to improve survival. We retrospectively studied a series of 23 consecutive patients with relapsing MM who underwent allogeneic transplantation after NMA-C and compared their outcome with those of patients who relapsed but were not allografted. Owing to these non-randomized available data, there was a need to correct for potential recruitment bias. The propensity score (PS) methodology allows coping with the presence of such a bias (Rosenbaum PR, Rubin DB. The central role of the propensity score in observational studies for causal effects. Biometrika 1983; 70:41–55). The idea was to model, for each patient with MM alive at 6 months after relapse, the probability of receiving NMA-C transplantation, according to a set of baseline characteristics (namely, baseline age, serum beta2 microglobulin level (b2M), and time to progression (TTP) after the first A-PBSCT). This PS was estimated using logistic regression. It was then used to match 1:1 patients with similar propensity to receive allograft, based on nearest neighbor matching using calipers of width 0.2. Data of patients treated in the MAG-95 and MAG-2002 trials were used. Standardized differences in covariates between subjects in the matched sample were computed, with imbalances tested by paired t tests. A random effects model was finally fitted in order to account for the matched nature of the data. 23 patients with MM in first (n=21) or second (n=2) relapse were treated with high dose therapy (melphalan 200 mg/m2 followed by A-PBSCT) preceding allogeneic PBSCT with a 2 Gy TBI NMA-C. Donors were HLA-identical siblings in 13 (56 %) patients. Six patients (26%) had a high b2M (>3 mg/L). Median age at allograft was 50 years (29–59 years). Median follow-up after allograft was 27.4 months (1.8–61.8 months). Post-allograft response was CR in 9 patients, VGPR in 8, PR in 4 and progressive disease (PD) in 2. TRM at one year was 13 % (1 severe GvHD, 2 infections). Two patients died from PD at 2 and 9 months after allograft respectively. Acute GvHD occurred in 19 patients (15 grade I/II, 4 grade III/ IV) and 11 developed chronic GvHD. Among the 10 patients (41.6%) who relapsed with a median of 10,7 months, 6 are alive with a median survival of 38.3 months. So far, 8 patients (34,7%) including 5 in CR and 3 in VGPR are still alive without relapse with a median follow-up of 36.8 months. From the 23 allografted patients, 21 matched pairs were successfully constituted. Expectedly, the distribution of age (mean difference: −0.97, p= 0.54), b2M (p=1.00), and TTP (mean difference: 3.2 months, p= 0.37) were not different between treated by allograft and untreated subjects. Based on these matched pairs, the estimated hazard ratio of death was 0.35 (95% confidence interval: 0.14–0.88, p=0.027) for allografted patients compared with non allografted. In conclusion, the PS is a useful tool for the analysis of observational data. Applied to MM data, it suggests that NMA-C allograft in MM patients in first relapse provides a high and durable response rate with a low TRM. These promising results must be further evaluated in clinical trials.

Measurement of midfemoral shaft geometry: repeatability and accuracy using magnetic resonance imaging and dual-energy X-ray absorptiometry.

Although macroscopic geometric architecture is an important determinant of bone strength, there is limited published information relating to the validation of the techniques used in its measurement. This study describes new techniques for assessing geometry at the midfemur using magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA) and examines both the repeatability and the accuracy of these and previously described DXA methods. Contiguous transverse MRI (Philips 1.5T) scans of the middle one-third femur were made in 13 subjects, 3 subjects with osteoporosis. Midpoint values for total width (TW), cortical width (CW), total cross-sectional area (TCSA), cortical cross-sectional area (CCSA), and volumes from reconstructed three-dimensional (3D) images (total volume [TV] and cortical volume [CVol]) were derived. Midpoint TW and CW also were determined using DXA (Lunar V3.6, lumbar software) by visual and automated edge detection analysis. Repeatability was assessed on scans made on two occasions and then analyzed twice by two independent observers (blinded), with intra- and interobserver repeatability expressed as the CV (CV +/- SD). Accuracy was examined by comparing MRI and DXA measurements of venison bone (and Perspex phantom for MRI), against "gold standard" measures made by vernier caliper (width), photographic image digitization (area) and water displacement (volume). Agreement between methods was analyzed using mean differences (MD +/- SD%). MRI CVs ranged from 0.5 +/- 0.5% (TV) to 3.1 +/- 3.1% (CW) for intraobserver and 0.55 +/- 0.5% (TV) to 3.6 +/- 3.6% (CW) for interobserver repeatability. DXA results ranged from 1.6 +/- 1.5% (TW) to 4.4 +/- 4.5% (CW) for intraobserver and 3.8 +/- 3.8% (TW) to 8.3 +/- 8.1% (CW) for interobserver variation. MRI accuracy was excellent for TV (3.3 +/- 6.4%), CVol (3.5 +/- 4.0%), TCSA (1.8 +/- 2.6%), and CCSA (1.6 +/- 4.2%) but not TW (4.1 +/- 1.4%) or CW (16.4 +/14.9%). DXA results were TW (6.8 +/- 2.7%) and CW (16.4 +/- 17.0%). MRI measures of geometric parameters of the midfemur are highly accurate and repeatable, even in osteoporosis. Both MRI and DXA techniques have limited value in determining cortical width. MRI may prove valuable in the assessment of surface-specific bone accrual and resorption responses to disease, therapy, and variations in mechanical loading.

Caliper and ultrasonographic measurements of bovine testicles and a mathematical formula for determining testicular volume and weight in vivo

This study quantified the relationship between calibrated caliper and ultrasonographic derived measurements of bovine testicles in vivo with actual testicular length, width, volume and weight. The prolate spheroid formula was tested to accurately predict testicular volume and a modification to predict weight. Ten bulls were employed to derive caliper and ultrasound testicle (n = 20) length and width measurements in vivo. Caliper length measurements were more reliable than ultrasound derived lengths, with correlations of r 2= 0.8023; P < 0.05 and r 2= 0.5111; P < .05, respectively. Width for both the calipers and ultrasound measurements when compared to actual width measurements were r 2= 0.7313; P < 0.05 and r 2= 0.8310; P < 0.05, respectively. The prolate spheroid formula is reliable in determining testicle (n = 116) volume (r 2= 0.8928; P < 0.05). Testicular volume and weight are highly correlated (r 2= 0.9776; P < 0.05); therefore, a modification of the prolate spheroid formula was used to predict weight (r 2= 0.9084; P < 0.05) against the actual weight. Caliper-derived length and width measurements used in the prediction of volume and weight had correlation coefficients against actual volume and weight of r 2= 0.5497; P < 0.05 and r 2= 0.6340; P < 0.05, respectively. Ultrasound in vivo measurements for prediction of testicular volume and testicular weight had a correlation of r 2= 0.3276; P < 0.05 and r 2= 0.6249; P <0.05, respectively. A testicular (n = 116) length to width ratio of 1.8:1 (SEM = 0.01) was determined for both slaughterhouse and castrated animals. Caliper measurements are reliable, inexpensive and much simpler to obtain than ultrasound determinations for in vivo testicle length, width, volume and weight. The two-dimensional measurement of length and width would be a more accurate predictor of testicle volume and weight than the onedimensional measurement of scrotal circumference (SC), especially in bulls with variation in testicular shape.

Comparison of Upper Arm Measurements by Use of Roentgenogram and Anthropometric Techniques

Abstract This research was undertaken to study those aspects of the upper left arm that could be readily differentiated by roentgenogram and anthropometric measures. High correlations were obtained between girth by tape and width by roentgenogram (0.95), between girth and width of muscle and bone (0.82), and between pinch caliper and roentgenogram width of adipose tissue (0.79). Low correlations resulted between adipose tissue measurements and girth and width of the upper arm.