Determining the impact of informed choice: separating treatment effects from the effects of choice and selection in randomized trials.

BACKGROUND: The Rucker 2-stage randomized trial (RCT) design and method allows treatment, preference, and selection effects to be estimated separately in clinical trials. OBJECTIVE: To understand the effect of patient choice on patient outcomes, the authors applied the Rucker design and analysis method. DESIGN: They used data from a trial of management strategies for women with atypical cells of undetermined significance (ASCUS) detected at routine cervical screening, in which informed choice using a decision aid was compared to no choice. SETTING: Women's health clinics across Australia. PATIENTS: Women aged 18 to 70 years (n = 314) with ASCUS. INTERVENTION: Women were randomized to either an informed choice of human papillomavirus (HPV) triage testing or repeat Pap testing or to no choice with random allocation to management by either option. MEASUREMENTS: Health-related quality of life (SF36) and satisfaction were measured over the course of management and up to 1 year after triage. RESULTS: Using the Rucker analysis, patients who received their choice had higher quality of life scores than those who did not choose (SF36 MCS, 6% higher, 6.0; 95% confidence interval: -0.6 to 12.9; P = 0.07; effect size 0.61 [moderate]). In contrast, the traditional RCT analysis suggested there was little difference in quality of life between the choice and no-choice trial arms. LIMITATIONS: The Rucker method assumes that the declared preferences for treatment in the choice arm are representative of the preferences that would have been observed in the no-choice arms if choice was available. CONCLUSIONS: The Rucker method should be used to estimate treatment, preference, and selection effects in randomized trials, as it adds to our understanding of the effect of choice on patient outcomes.

Psychosocial outcomes of three triage methods for the management of borderline abnormal cervical smears: an open randomised trial.

OBJECTIVE: To assess which of three triage strategies for women with borderline abnormal cervical smear results in the best psychosocial outcomes. DESIGN: Pragmatic, non-blinded, multicentre, randomised controlled trial. SETTING: 18 family planning clinics across Australia, covering both urban and rural areas, between January 2004 and October 2006. PARTICIPANTS: Women aged 16-70 years (n=314) who attended routine cervical screening and received a borderline cervical smear. INTERVENTIONS: Patients were randomly assigned to human papillomavirus (HPV) DNA testing (n=104), a repeat smear test at six months (n=106), or the patient's informed choice of either test supported by a decision aid (n=104). Psychosocial outcomes were assessed at multiple time points over 12 months by postal questionnaire. MAIN OUTCOME MEASURES: We assessed health related quality of life (SF36 mental health subscale), cognitive effects (such as perceived risk of cervical cancer, intrusive thoughts), affective outcomes (general anxiety [state-trait anxiety inventory]), specific anxiety about an abnormal smear (cervical screening questionnaire), and behavioural outcomes (sexual health behaviour and visits to the doctor) over 12 months of follow-up. RESULTS: At two weeks, some psychosocial outcomes were worse for women allocated to HPV testing compared with those in the smear testing group (SF36 vitality subscale: t=-1.63, df=131, P=0.10; intrusive thoughts chi(2)=8.14, df=1, P<0.01). Over 12 months, distress about the abnormal smear was lowest in women allocated to HPV testing and highest in the repeat smear testing group (t=-2.89, df=135, P<0.01). Intrusive thoughts were highest in patients allocated to HPV testing (25%, compared with 13% in the informed choice group; difference=12%, 95% CI -1.1% to 25.1%). Women in the HPV DNA group and the informed choice group were more satisfied with their care than women allocated to repeat smear testing. CONCLUSIONS: Although the psychosocial effect was initially worse for women allocated to HPV triage, over the full year of follow-up this intervention was better for women's psychosocial health than repeat smear testing. Offering informed choice could have a small advantage for cognitive outcomes, but in view of the additional effort and logistical complexity that this intervention requires, HPV testing alone can be justified for most women. TRIAL REGISTRATION: actr.org.au Identifier: 12605000111673.

HPV testing versus repeat Pap testing for the management of a minor abnormal Pap smear: evaluation of a decision aid to support informed choice.

OBJECTIVE: To examine women's informed preference for the management of a mildly abnormal Pap smear and the impact of a decision aid. METHODS: Women (n=106) were given a choice of management supported by a decision aid and surveyed before, and after decision making to evaluate predictors of choice and decision aid impact. RESULTS: HPV triage was preferred by most women (65%) although a substantial minority selected repeat Pap testing (35%). Women who chose HPV triage were more likely to have had children, have had a previous abnormal Pap smear and were more distressed than women who chose a repeat Pap test. In total, 68% of women made an informed choice. Rapid timing of follow-up was important for women choosing HPV testing. The lower chance of colposcopy and greater opportunity for regression, were rated as important by women choosing Pap testing. Decisional conflict was lower among women who chose HPV triage. No other differences in short-term psychological outcomes were found. CONCLUSION: The decision aid supported informed choice among the majority of women. Women tailored their choice to their practical, health and psychological needs. PRACTICE IMPLICATIONS: Offering women an informed choice for a mildly abnormal Pap smear may enable women to select the management that best suits their circumstances.

Three methods to construct predictive models using logistic regression and likelihood ratios to facilitate adjustment for pretest probability give similar results.

OBJECTIVE: To compare three predictive models based on logistic regression to estimate adjusted likelihood ratios allowing for interdependency between diagnostic variables (tests). STUDY DESIGN AND SETTING: This study was a review of the theoretical basis, assumptions, and limitations of published models; and a statistical extension of methods and application to a case study of the diagnosis of obstructive airways disease based on history and clinical examination. RESULTS: Albert's method includes an offset term to estimate an adjusted likelihood ratio for combinations of tests. Spiegelhalter and Knill-Jones method uses the unadjusted likelihood ratio for each test as a predictor and computes shrinkage factors to allow for interdependence. Knottnerus' method differs from the other methods because it requires sequencing of tests, which limits its application to situations where there are few tests and substantial data. Although parameter estimates differed between the models, predicted "posttest" probabilities were generally similar. CONCLUSION: Construction of predictive models using logistic regression is preferred to the independence Bayes' approach when it is important to adjust for dependency of tests errors. Methods to estimate adjusted likelihood ratios from predictive models should be considered in preference to a standard logistic regression model to facilitate ease of interpretation and application. Albert's method provides the most straightforward approach.