Measurement invariance of the kidney disease and quality of life instrument (KDQOL-SF) across Veterans and non-Veterans

<p>Abstract</p> <p>Background</p> <p>Studies have demonstrated that perceived health-related quality of life (HRQOL) of patients receiving hemodialysis is significantly impaired. Since HRQOL outcome data are often used to compare groups to determine health care effectiveness it is imperative that measures of HRQOL are valid. However, valid HRQOL comparisons between groups can only be made if instrument invariance is demonstrated. The Kidney Disease Quality of Life-Short Form (KDQOL-SF) is a widely used HRQOL measure for patients with chronic kidney disease (CKD) however, it has not been validated in the Veteran population. Therefore, the purpose of this study was to examine the measurement invariance of the KDQOL-SF across Veterans and non-Veterans with CKD.</p> <p>Methods</p> <p>Data for this study were from two large prospective observational studies of patients receiving hemodialysis: 1) Veteran End-Stage Renal Disease Study (VETERAN) (N = 314) and 2) Dialysis Outcomes and Practice Patterns Study (DOPPS) (N = 3,300). Health-related quality of life was measured with the KDQOL-SF, which consists of the SF-36 and the Kidney Disease Component Summary (KDCS). Single-group confirmatory factor analysis was used to evaluate the goodness-of-fit of the hypothesized measurement model for responses to the subscales of the KDCS and SF-36 instruments when analyzed together; and given acceptable goodness-of-fit in each group, multigroup CFA was used to compare the structure of this factor model in the two samples. Pattern of factor loadings (configural invariance), the magnitude of factor loadings (metric invariance), and the magnitude of item intercepts (scalar invariance) were assessed as well as the degree to which factors have the same variances, covariances, and means across groups (structural invariance).</p> <p>Results</p> <p>CFA demonstrated that the hypothesized two-factor model (KDCS and SF-36) fit the data of both the Veteran and DOPPS samples well, supporting configural invariance. Multigroup CFA results concerning metric and scalar invariance suggested partial strict invariance for the SF-36, but only weak invariance for the KDCS. Structural invariance was not supported.</p> <p>Conclusions</p> <p>Results suggest that Veterans may interpret the KDQOL-SF differently than non-Veterans. Further evaluation of measurement invariance of the KDQOL-SF between Veterans and non-Veterans is needed using large, randomly selected samples before comparisons between these two groups using the KDQOL-SF can be done reliably.</p

Importance of obesity, race and age to the cardiac structural and functional effects of hypertension

AbstractObjectives. The purpose of this study was to determine the effects of obesity and its interaction with age, race and the magnitude of blood pressure elevation in a large cohort of patients with mild to moderate hypertension and a high prevalence of left ventricular hypertrophy.Background. Obesity, race and age each have important effects on the incidence and severity of hypertension and may contribute to the effects of blood pressure elevation on the cardiac manifestations of hypertension.Methods. Left ventricular structure and function were assessed with two-dimensional targeted M-mode echocardiography in 692 men with mild to moderate hypertension (average blood pressure 153/100 mm Hg), and the data were compared in relation to obesity (determined from body mass index), age, race, blood pressure, physical activity, plasma renin activity, urinary sodium excretion, hematocrit, heart rate and serum lipids.Results. Left ventricular hypertrophy was common (630% with increased left ventricular mass, 22% with left ventricular hypertrophy on the electrocardiogram [ECG]). On multivariable regression analysis, body mass index was the strongest predictor of left ventricular mass and magnified the slope relation of blood pressure to left ventricular mass. Despite a greater prevalence of ECG left ventricular hypertrophy in blacks (31%) than in whites (10%), left ventricular mass and echocardiographic prevalence of left ventricular hypertrophy did not differ by race. However, septal, posterior left ventricular and relative wall thickness were greater in black than in white men.Conclusions. Obesity is the strongest clinical predictor of left ventricular mass and left ventricular hypertrophy la men, even in those with mild to moderate hypertension of sufficient severity to be associated with a high prevalence of left ventricular hypertrophy. Moreover, independent effects of systolic blood pressure on left ventricular mass an amplified by obesity. Although race does not affect left ventricular mass or the prevalence of left ventricular hypertrophy, black race is associated with greater relative wall thickness, itself a predictor of unfavorable cardiovascular outcome

Correction: Single-Drug Therapy for Hypertension in Men

To the Editor: During further analysis of the data used in our study of single-drug therapy for hypertension in men (April 1, 1993, issue), 1 we discovered two errors in the computer program; these errors affected the results that we reported in Figures 2 and 3 of the article. One error permitted a small group of patients who had not completed one year of maintenance therapy to be excluded from the analysis, even though we had planned an intention-to-treat analysis. The second error was due to an unrecognized deletion of an entire line of code that provided the definition of treatment . . 

Lessons from combination therapy in veterans affairs studies

A subset of 102 patients of an original cohort of 1292 with stage 1 to 2 hypertension was characterized by having failed to achieve goal blood pressure (< 90 mm Hg diastolic) after treatment with two single antihypertensive drugs. These patients were given a combination of the two drugs on which they had failed to achieve blood pressure goal when they were administered as single-drug therapy. The drugs were hydrochlorothiazide, atenolol, captopril, diltiazem-SR, clonidine, and prazosin. We examined the responses in each of the drug combination categories by the order that the drugs were administered by estimated total response rates for the combinations, and by age and race. The order of drug administration did have an effect for some of the drug pairs. This was of two types: 1) different results for each member of the pair, but the same combination result; and 2) different end result of the combination. An example of the first type is that prazosin had only a 6% response rate in patients who had failed on diltiazem, while diltiazem had a 22% response rate in patients who had failed on prazosin. Nevertheless, the combinations yielded the same total responses (86% and 34%) regardless of order. An example of the second type is that captopril-diltiazem was less effective in total response than dialtiazem-captopril (88% ν 97%). Differences were seen in the response to combinations in the race and age groups. There were ordering differences of type similar to those described above. We conclude that combination drug therapy is highly effective even when the individual components have failed and that some differences in response by order of drug administration may occur

Comparison of Effects of Antihypertensive Drugs on Heart Rate: Changes From Baseline by Baseline Group and Over Time

Baseline heart rate is becoming recognized as a predictor of cardiovascular risk. Various antihypertensive drugs have differing effects on heart rate. A randomized controlled clinical trial of 1292 ambulatory men with stage 1 or 2 hypertension was conducted in 15 Veterans Affairs medical centers. Patients were treated with hydrochlorothiazide, atenolol, captopril, clonidine, diltiazem, prazosin, or placebo for up to 2 years. Heart rates were measured at baseline, the end of titration, 1 year, and 2 years. Data were also stratified by baseline heart rate. A subset of patients had heart rate also determined by electrocardiogram. All drugs except prazosin reduced heart rate from baseline; additional small decreases were obtained over time with hydrochlorothiazide and placebo. The decrease initially achieved with clonidine was attenuated over time. The overall reduction in heart rate was greatest for atenolol (−12.2 beats/min) and least for prazosin (+3.8 beats/min). Only atenolol effected a further reduction of heart rate for patients whose baseline rate was ≤65 beats/min. All drugs reduced heart rate when the baseline was ≥85 beats/min. Data derived by electrocardiogram yielded similar results. The drugs used in this study differ in their ability to reduce heart rate, sustain that reduction over time, and to change heart rate in groups with high or low rates at baseline. The importance of these comparative changes as independent cardiac risk factor variables remains to be determined