REGRESSION TO THE MEAN: METHODOLOGICAL ISSUES FOR EVALUATION OF HEART RATE VARIABILITY VARIABLES FOR STRESS ASSESSMENT

There is now a substantial body of evidence linking the baseline level of heart rate variability (HRV) with the magnitude of stress-induced reduction in respiratory sinus arrhythmia. However, it remains to be proved to what extent these interindividual differences in stress responses may be attributed to the statistical phenomenon of regression to the mean (RTM). We sought to test the hypothesis that the statistical artifact RTM explains pan of the baseline effect. Heart rate recording was carried out in 1156 volunteers. To obtain an estimate of the stress response. 148 persons were randomly selected. Participants were monitored on a rest day and just before an academic examination for state anxiety and HRV. Participants were divided into quartiles according to baseline HRV levels and were compared for response to academic stress. We observed a significant reduction in HRV in subjects with a high baseline HRV (> 75th percentile), while a significant increase was found in the group with low baseline HRV. Regression analysis demonstrated that the value of baseline HRV correlated with the magnitude of stress reaction consistent with the RTM model. Baseline-adjusted ANCOVA does not reveal significant intergroup differences in the changes hi heart rate (HR) and HRV from rest to exam. RTM-adjusted estimates confirmed an exam effect for HR and HRV. The results of our study strongly support RTM as the source of variability of stress-related changes in HRV.

Possible New Symptoms of Tobacco Withdrawal III: Reduced Positive Affect—A Review and Meta-analysis

Introduction Most descriptions of tobacco withdrawal have not changed in >30 years despite new research. This meta-analysis tested whether abstinence leads to decreased positive affect (PA) because abstinence-induced symptom changes are a core feature of the tobacco withdrawal syndrome. In addition, we examined whether reduced PA was due to withdrawal (ie, temporary decrease in a “U-shaped” curve) or offset (ie, return to baseline) effect. Methods Our main inclusion criterion was a prospective within-participant test of change in PA during abstinence conditions among people who smoke cigarettes daily who were not using a cessation medication. Our search of PubMed, PsycINFO, and personal libraries yielded a total of 32 tests with 2054 participants. Results There was a medium effect size indicating an overall decrease in PA following abstinence from cigarettes (Cohen’s d = −0.40, 95% CI = −0.30 to −0.49). There was large heterogeneity (I2 = 70.7%). Most (79%) of the 24 trials that conducted significance tests reported that reduction in PA was significant. Seven tests were adequately designed to detect a withdrawal versus offset effect. Over half (57%) displayed a U-shaped curve for abstinence-induced change in PA indicative of a withdrawal symptom rather than offset effect. Conclusions Abstinence from cigarettes is associated with a decrease in PA. Whether low PA should be added to withdrawal measures and diagnostic criteria requires replication of the time-course of change in PA and tests of whether abstinence-induced changes in PA and negative affect occur independently. Implications Though there was substantial heterogeneity among trials, our findings suggest that (1) abstinence from cigarettes decreases positive affect and (2) this decrease may represent a withdrawal effect (vs. an offset effect). However, it is unclear whether abstinence-induced losses in positive affect are independent from increased negative affect.

Customer Ethnic Bias in Service Encounters

As ethnic diversity continues to rise, customer bias in interethnic service encounters becomes an increasingly problematic issue for the parties involved, the service firms, and society at large. Against this background, the aim of our research is to examine ethnically biased customer responses, their key psychological mechanisms, and the effectiveness of enacted service scripts to shape interethnic service encounters. Building on the aversive racism framework and homophily theory, we propose a baseline effect of majority customers’ ethnic bias toward minority employees in the form of less positive behaviors in interethnic service encounters. In an initial laboratory study, we use experimental video simulations of frontline service encounters and confirm the robustness of this effect across two replications. In a subsequent field experiment, we test an extended framework of customer responses to interethnic service encounters, finding that customers’ experience of rapport and identification with the firm represent two serial mediators that facilitate the effects of interethnic service encounters on customer loyalty intentions. Together, these contributions enrich our understanding of how psychological mechanisms facilitate the incidence of ethnically biased customer behavior and also provide insights into viable ways to improve such encounters.

Interindividual variability in HRV reactivity: autonomic flexibility or regression to the mean?

ObjectiveThere is now a substantial body of evidence linking the baseline level of heart rate variability (HRV) with the magnitude of stress-induced reduction in respiratory sinus arrhythmia. However, it remains to be proved to what extent these interindividual differences in stress responses may be attributed to the statistical phenomenon of regression to the mean (RTM). We sought to test the hypothesis that the statistical artifact RTM explains part of the baseline effect.ApproachHeart rate recording was carried out in 1,156 volunteers. To obtain an estimate of the stress response, 148 persons were randomly selected. Participants were monitored on a rest day and just before an academic examination for state anxiety and HRV. Participants were divided into quartiles according to baseline HRV levels and were compared for response to academic stress.Main resultsWe observed a significant reduction in HRV in subjects with a high baseline HRV (> 75th percentile), while a significant increase was found in the group with low baseline HRV. Regression analysis demonstrated that the value of baseline HRV correlated with the magnitude of stress reaction consistent with the RTM model. Baseline-adjusted ANCOVA does not reveal significant intergroup differences in the changes in heart rate (HR) and HRV from rest to exam. RTM-adjusted estimates confirmed an exam effect for HR and HRV.SignificanceThe results of our study strongly support RTM as the source of variability of stress-related changes in HRV.

Venous thromboembolism after total knee replacement or total hip replacement: what can be learnt from root-cause analysis?

INTRODUCTION Because of the high risk of venous thromboembolism (VTE) in total hip replacement (THR) and total knee replacement (TKR), guidelines are used widely to enhance effective (yet safe) prophylaxis. If patients develop VTEs despite use of such guidelines, then the reasons are that the guidelines were: (i) followed but the VTE occurred anyway; (ii) not implemented appropriately. All VTEs are assessed routinely by root-cause analysis (RCA). METHODS The records and subsequent RCA reports for each patient who experienced clinically significant VTE after THR or TKR were reviewed. We established adherence to the guidelines (deemed to be ‘unavoidable’ with scope to improve the guidelines) and non-adherence (deemed to be ‘avoidable’ with scope to improve implementation). RESULTS Of 2,214 patients undergoing THR (n=1,330) or TKR (n=884), 25 (1.13%) experienced VTE. Four THR patients experienced VTE (2 of which were avoidable) and 21 TKR patients experienced VTE (5 of which were avoidable). There were significantly more VTEs in TKR patients than THR patients (p<0.0001). CONCLUSIONS A proportion of patients will experience VTE even if guidelines are followed (a baseline effect). Administration of chemical prophylaxis earlier might reduce this baseline effect further. This approach should be taken cautiously with due respect for the alternative risk of bleeding. Improvement in hospital routine may reduce the risk of VTE yet further.

PTH modulation of NCC activity regulates TRPV5 Ca2+ reabsorption

Since parathyroid hormone (PTH) is known to increase transient receptor potential vanilloid (TRPV)5 activity and decrease Na+-Cl− cotransporter (NCC) activity, we hypothesized that decreased NCC-mediated Na+ reabsorption contributes to the enhanced TRPV5 Ca2+ reabsorption seen with PTH. To test this, we used mDCT15 cells expressing functional TRPV5 and ruthenium red-sensitive 45Ca2+ uptake. PTH increased 45Ca2+ uptake to 8.8 ± 0.7 nmol·mg−1·min−1 ( n = 4, P < 0.01) and decreased NCC activity from 75.4 ± 2.7 to 20.3 ± 1.3 nmol·mg−1·min−1 ( n = 4, P < 0.01). Knockdown of Ras guanyl-releasing protein (RasGRP)1 had no baseline effect on 45Ca2+ uptake but significantly attenuated the response to PTH from a 45% increase (6.0 ± 0.2 to 8.7 ± 0.4 nmol·mg−1·min−1) in control cells to only 20% in knockdown cells (6.1 ± 0.1 to 7.3 ± 0.2 nmol·mg−1·min−1, n = 4, P < 0.01). Inhibition of PKC and PKA resulted in further attenuation of the PTH effect. RasGRP1 knockdown decreased the magnitude of the TRPV5 response to PTH (7.9 ± 0.1 nmol·mg−1·min−1 for knockdown compared with 9.1 ± 0.1 nmol·mg−1·min−1 in control), and the addition of thiazide eliminated this effect (a nearly identical 9.0 ± 0.1 nmol·mg−1·min−1). This indicates that functionally active NCC is required for RasGRP1 knockdown to impact the PTH effect on TRPV5 activity. Knockdown of with no lysine kinase (WNK)4 resulted in an attenuation of the increase in PTH-mediated TRPV5 activity. TRPV5 activity increased by 36% compared with 45% in control ( n = 4, P < 0.01 between PTH-treated groups). PKC blockade further attenuated the PTH effect, whereas combined PKC and PKA blockade in WNK4KD cells abolished the effect. We conclude that modulation of NCC activity contributes to the response to PTH, implying a role for hormonal modulation of NCC activity in distal Ca2+ handling.

Survival analysis: a tool in the study of post-harvest diseases in peaches

Survival analysis is applied when the time until the occurrence of an event is of interest. Such data are routinely collected in plant diseases, although applications of the method are uncommon. The objective of this study was to use two studies on post-harvest diseases of peaches, considering two harvests together and the existence of random effect shared by fruits of a same tree, in order to describe the main techniques in survival analysis. The nonparametric Kaplan-Meier method, the log-rank test and the semi-parametric Cox's proportional hazards model were used to estimate the effect of cultivars and the number of days after full bloom on the survival to the brown rot symptom and the instantaneous risk of expressing it in two consecutive harvests. The joint analysis with baseline effect, varying between harvests, and the confirmation of the tree effect as a grouping factor with random effect were appropriate to interpret the phenomenon (disease) evaluated and can be important tools to replace or complement the conventional analysis, respecting the nature of the variable and the phenomenon.

Validation of the supplementary quality of life questionnaire for mouth/throat and hand/foot soreness.

9574 Background: PISCES is a randomized crossover trial evaluating patient preference of pazopanib versus sunitinib in advanced/ metastatic renal cell carcinoma. The Supplementary Quality of Life Questionnaire (SQLQ) was developed for this trial to assess hand/foot soreness and mouth/throat soreness (MTS). The objective of this project is to validate the SQLQ. Methods: SQLQ was administered at baseline and every two weeks thereafter. EQ-5D was administered at baseline, during the washout period, and end of second treatment period. Treatment arms were collapsed for validation. SQLQ assesses severity of MTS (1 item), limitations due to MTS (5 items), severity of hand soreness (1 item), severity of foot soreness (1 item), limitations due to foot soreness (5 items) and ability to work (1 item). Cronbach’s coefficient alpha was used to evaluate the internal consistency reliability of the multi-item subscales.T-tests compared scores between groups defined by performance status (0 versus 1) and number of metastatic sites (0/1 versus 2+) at baseline. Effect sizes (ES = mean difference / pooled standard deviation) were calculated. Results: Of 169 patients randomized, data was available on 168. Over 80% of on-study patients completed the SQLQ at each assessment. Cronbach’s coefficient alpha was ≥ 0.80 for both limitations subscales at all assessments except baseline (limitations due to MTS). Both scores differentiated between performance status groups at baseline with ES > 0.40 (p<0.05). Scores significantly differed by severity of soreness with large ES of 0.9-2.1. Moderate correlations with EQ-5D were observed for limitations scores; correlations were smaller for soreness ratings. MTS and limitations due to MTS worsened after baseline with moderate – large ES; moderate ES was observed for changes in other scores. Limitation change scores were minimal in groups with no change in soreness rating; patients with worsened soreness reported similarly worsened limitations due to soreness with moderate – large ES. Conclusions: SQLQ is a valid and responsive measure of MTS, hand/foot soreness, and limitations due to soreness. Use of the SQLQ in future clinical trials will provide further external validation.