The Childhood Asthma Control Test: retrospective determination and clinical validation of a cut point to identify children with very poorly controlled asthma.

BACKGROUND: The Childhood Asthma Control Test (C-ACT) has demonstrated validity in classifying children aged 4 to 11 years as having either "well-controlled" or "not well-controlled" asthma. However, new asthma management guidelines distinguish 3 levels of asthma control. OBJECTIVE: We sought to determine a second cut point on the C-ACT to identify children with "very poorly controlled" asthma. METHODS: Binomial logistic regression was performed on data from 671 children. The specialist's rating of control was the criterion measure. Specialists' severity ratings, specialists' assessment of therapy, and FEV(1) percent predicted were used to assess the clinical validity of the cut point. RESULTS: A cut point of 12 was selected because it correctly classified the highest percentage of participants (66.3%) as having "very poorly controlled" (vs "not well controlled") asthma and demonstrated high specificity (89.8%) and moderate positive predictive value (69.1%). Children scoring 12 or less versus 13 to 19 had lower mean FEV(1) percent predicted (79.8% vs 92.6%, P = .0002) and were more frequently stepped up in therapy (72.9% vs 53.6%, P = .0131) and rated as having severe asthma (13.6% vs 4.5%, P = .0005). One month later, significant differences in C-ACT scores and lung function between these 2 groups persisted. The mean C-ACT score of participants classified as "very poorly controlled" was significantly lower than that of participants classified as "not well-controlled" (17.2 vs 20.3, respectively; P = .0001). CONCLUSION: A second cut point of 12 or less on the C-ACT identifies children with the lowest level of control, who are at risk for poorer outcomes, and is conceptually consistent with the classification of "very poorly controlled" asthma adopted by asthma management guidelines.

The minimally important difference of the Asthma Control Test.

BACKGROUND: The Asthma Control Test (ACT) has been well validated, but a minimally important difference (MID) has not been established. OBJECTIVE: We sought to identify an MID for the ACT. METHODS: Data come from 4 independent samples of adult asthmatic patients. Distributional methods for determining the MID included 0.5 SD, 1 SEM, and 2 SEM. Anchor-based methods assessed the relationship of differences in ACT scores to (1) self-reported asthma severity, (2) asthma episode frequency in the past 4 weeks, (3) physician ratings of asthma control, (4) physician recommendation of a change in therapy, (5) FEV(1), (6) the risk over the next 12 months of excess short-acting beta-agonist use and exacerbations, and (7) patient-defined changes in asthma course over 3 months. RESULTS: Four thousand one hundred eighteen patients completed the ACT. The 0.5 SD criterion for MID ranged from 2.03 to 2.45 points (mean, 2.2 points). The 1 SEM criterion ranged from 1.77 to 2.05 points (mean, 1.88 points), and the 2 SEM criterion ranged from 3.55 to 4.10 points (mean, 3.75 points). Differences in mean ACT scores across patient groups differing on criterion measures ranged from 1.06 to 5.28 points (mean, 3.1 points). Predictive analyses showed that a difference of 3 points on the ACT was associated with a subsequent 76% increased risk (95% CI, 73% to 79%) of excess short-acting beta-agonist use and a 33% increased risk (95% CI, 31% to 35%) of exacerbations. CONCLUSION: The data support an MID for the ACT of 3 points.

Patient-reported outcome instrument selection: designing a measurement strategy.

OBJECTIVE: To discuss issues in the design of a measurement strategy related to the use of patient-reported outcomes (PROs) in support of a labelling claim. METHODS: In association with the release by the US Food and Drug Administration of its draft guidance on the use of PROs to support labeling claims, the Mayo/FDA Patient-Reported Outcomes Consensus Writing Group was formed. This paper, part of a series of manuscripts produced by the Writing Group, focuses on designing a PRO measurement strategy. RESULTS: Developing a PRO measurement strategy begins with a clear statement about the proposed label claim that will derive from the PRO data. Investigators should identify the relevant domains to measure, develop a conceptual framework, identify alternative approaches for measuring the domains, and synthesize the information to design the measurement strategy. Often, there is not an already existing single instrument that has been developed and validated for the purposes of a given study. In such cases, investigators may consider supplementing an already existing questionnaire with additional scales or questions, modifying already existing instruments for a new application or patient population, or developing a new instrument altogether. The level of revalidation required for modifications and adaptations depends on the extent of the changes made. Revalidation requirements may range from cognitive testing/debriefing to confirm that subjects respond to the new instrument as expected to full-scale reliability and validity evaluations. CONCLUSION: A position of "reasonable pragmatism" is recommended such that the best available measurement strategy be considered as evidence for labeling.

Economic efficiency of genetic screening to inform the use of abacavir sulfate in the treatment of HIV.

BACKGROUND: Abacavir sulfate (abacavir) is associated with a hypersensitivity reaction (HSR) that affects 5-8% of patients. While serious complications are rare, failure to identify it, or abacavir re-challenge following HSR, can be fatal. Genetic screening for HLA-B*5701 can identify patients who are likely to experience an HSR and reduces the incidence of the reaction. OBJECTIVE: We assessed the intrinsic and practical value, from the US healthcare system perspective, of prospective HLA-B*5701 screening among a population of antiretroviral-naive patients without elevated risk factors for cardiovascular disease, plasma HIV RNA >100,000 copies/mL, or pre-existing renal insufficiency. METHODS: Two approaches were used to evaluate the costs and benefits of prospective screening. First, the efficiency of HLA-B*5701 screening compared with no screening prior to abacavir initiation (intrinsic value of screening) was evaluated using a 60-day decision-tree model. Next, the practical value of screening was assessed using a lifetime discrete-event simulation model that compared HLA-B*5701 screening prior to abacavir use versus initiation with a tenofovir-containing regimen. Screening-effectiveness parameters were taken from an open-label trial that incorporated screening prior to abacavir initiation and other published studies. Treatment efficacy was derived from clinical trials. Modelling assumptions, costs ($US, year 2007 values) and other parameters were derived from published sources, primary data analysis and expert opinion. Multiple one-way sensitivity and scenario analyses were performed to assess parameter uncertainty. The primary outcome measure for the short-term screening versus no screening analysis was cost per patient. For the long-term analysis, outcomes were presented as QALYs. Costs and effects were discounted at 3% per year. RESULTS: Over the first 60 days of treatment, prospective screening prior to abacavir initiation cost an additional $US17 per patient and avoided 537 HSRs per 10,000 patients. The per-patient cost of screening was sensitive to the cost of the genetic test, HSR costs and screening performance. In the lifetime model, screening-informed abacavir use was more effective and less costly than initiation with a tenofovir-containing regimen in the base case and in sensitivity analyses. CONCLUSIONS: Our results suggest that prospective HLA-B*5701 screening prior to abacavir initiation produces cost savings and should become a standard component of HIV care.

A study of HIV provider attitudes toward HLA-B 5701 testing in the United States.

Screening for HLA-B 5701 reduces the risk of developing an abacavir hypersensitivity reaction (ABC HSR) and is recommended in all patients before initiating highly active antiretroviral therapy (HAART) with abacavir. Between September 2007 and March 2008 we conducted a study of the attitudes and practice patterns of HIV providers in the United States to identify barriers to HLA-B 5701 testing in clinical practice. Study participants who completed an educational program could receive HLA-B 5701 test kits for use in their clinical practice. Surveys were administered before and after the educational program. A total of 477 HIV providers registered to participate in the survey, and 134 providers tested a total of 874 HIV-infected subjects, of which 6% (49/874) were HLA-B 5701 positive. Of 433 providers who completed the preeducation survey, 97% indicated that the test provided clinical value and 77% anticipated barriers to testing, with cost/reimbursement the most frequently cited. Among 202 providers who completed the posteducation survey, perceptions of the test's value remained largely unchanged while the proportion of providers who anticipated or encountered barriers to testing decreased. Of providers who used HLA-B 5701 test kits, 86% (115/134) found it "very easy" or "easy" to obtain test results, 95% (127/134) found it "very easy" or "easy" to interpret results, and 89% (119/134) indicated that they planned to continue HLA-B 5701 testing after the study. The results of this study suggest that HLA-B 5701 testing is easy to use in clinical practice and is a valuable tool to help reduce the risk of developing ABC HSR.

Benefits, risk, and uncertainty: preferences of antiretroviral-naïve African Americans for HIV treatments.

While African Americans in the United States are disproportionately affected by HIV, they are less likely to take antiretroviral therapies. Different first-line antiretroviral therapies are associated with short-term and long-term adverse event (AE) risks. We estimated the willingness of antiretroviral-naïve, HIV-positive African Americans to accept risks of acute AEs with known outcomes and long-term AEs with uncertain outcomes in exchange for virologic suppression. We estimated the relative importance of short-term and long-term AE risks. Two hundred thirty-five subjects were recruited through eight clinics in the United States. One hundred fifty-eight subjects met study inclusion criteria. One hundred fifty-three subjects completed a series of choice-format conjoint trade-off tasks. In each task, subjects were asked to choose between two hypothetical treatments with varying levels of virologic failure, risks of hypersensitivity reaction, decreases in bone mineral density (BMD), and renal impairment, and outcome uncertainty associated with the risks of decreased BMD and renal impairment. Attributes were expressed as probabilities of occurrence. We calculated the relative importance of each AE and the level of risk subjects would accept to reduce the risk of virologic failure. Subjects indicated that short-term AEs with relatively certain outcomes are preferred to long-term AEs with uncertain outcomes. Subjects were strongly averse to the risk of decreased BMD that could not be treated successfully or when the outcome was uncertain and to the risk of renal impairment that could not be treated successfully. Subjects were willing to accept increased risks of AEs in exchange for lower risk of virologic failure.

A comparison of techniques for eliciting patient preferences in patients with benign prostatic hyperplasia.

PURPOSE: We compared the Health Utility Index (HUI), EuroQol (EQ-5D) and time trade-off methods to identify the most suitable technique for collecting preference data in a clinical trial of patients with benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: A total of 29 men with symptomatic BPH were interviewed by a single trained interviewer who collected demographic data and administered EQ-5D and time trade-off questionnaires. Participants self-administered the HUI and a symptom severity index, the International Prostate Symptom Score (I-PSS) questionnaire. Utility values for current patient health states obtained from the HUI, EQ-5D and time trade-off questionnaires were compared and their relationship with I-PSS data was examined using Spearman's correlation coefficients. Administration time and patient assessments of the relevance of the questions were also compared for the 3 methods. RESULTS: Although mean utility values for HUI, EQ-5D and 1-year time trade-off were similar, only utility values elicited using time trade-off with a 1-year time frame significantly correlated with symptom scores. The 1 and 10-year time trade-off derived values were reasonable predictors of the I-PSS with multiple correlation coefficient values of 0.379 and 0.265, respectively. All participants indicated that the HUI and EQ-5D were appropriate for assessing BPH, while approximately 10% considered time trade-off questions irrelevant. Average completion time for the HUI, time trade-off and EQ-5D questionnaires was 31, 25 and 10 minutes, respectively. CONCLUSIONS: Because only time trade-off resulted in utility values that significantly correlated with symptom scores, we recommend its use for estimating utility in clinical trials of BPH.