Modeling lesion counts in multiple sclerosis when patients have been selected for baseline activity.

The number of new gadolinium-enhancing lesions discovered via magnetic resonance imaging is a well-established outcome for multiple sclerosis studies, especially Phase II Studies. Due to the high cost of magnetic resonance imaging scans, many investigators select participants for the presence of lesions. While this selection procedure is thought to improve the power of inferences, the effect of screening for baseline activity on parameter estimation and interval coverage has not yet been examined. The objective of this study was to investigate the performance of the negative binomial distribution for modeling lesion count data in multiple sclerosis when patients have been selected for activity on a baseline scan. We performed computer simulations to investigate the influence of the screening process on inferences made using a negative binomial model about treatment effects in two independent samples. We also demonstrate how the statistical properties of screening can be incorporated into trial design. We demonstrate that when the negative binomial distribution is used to model lesion counts, while screening for baseline activity improves point estimation, this practice also has the potential to decrease interval coverage and inflate the Type I error rate. For data that is to be modeled using a negative binomial distribution, screening for baseline activity can create a trade-off between cost effectiveness and a higher than desired false positive rate that must be carefully considered in planning Phase II trials.

A process evaluation of the implementation of a computer-based, health provider-delivered HIV-prevention intervention for HIV-positive men who have sex with men in the primary care setting.

There is increasing interest in using healthcare providers to deliver HIV-prevention services to their patients. Unfortunately, lack of counselling skills and time constraints within busy clinics serve as barriers to such efforts. The Providers Advocating for Sexual Health Initiative (PASHIN) study used state-of-the-art computer technology to assess each participant's risk behaviours and to determine the patient's readiness for changing each behaviour. The computer synthesized the participant-entered data, determined the targeted risk behaviour and printed a behavioural theory-based provider advice sheet and a 3-point patient prescription for the targeted risk behaviour. Since the intervention does not require providers to spend time performing a detailed sexual-risk assessment and it does not require providers to have received extensive counselling training, it has the potential to minimize some of the barriers associated with provider-delivered interventions. Thus, the purpose of this process evaluation was to assess how the PASHIN intervention was implemented in the field, including issues such as the fidelity of implementation and health providers' views on and experience with implementing the intervention. Overall, the results demonstrated that the computer-based, provider-delivered intervention was successfully delivered by providers within the context of regularly scheduled treatment sessions with HIV-positive men who have sex with men (MSM) patients. The majority of providers (79.4%) and patients (83.5%) reported that the quality of HIV-prevention services delivered during these sessions was 'good'. The majority of the providers also reported that they had received adequate training, felt more confident in communicating HIV-prevention issues with their patients and provided more HIV-prevention counselling to their patients, due to the project. However, the experience of delivering HIV-prevention counselling during an 18-month period did not appear to change providers' attitudes toward a provider-delivered HIV-prevention intervention nor their belief in the effectiveness of HIV prevention in general. Future studies should focus on how to enhance providers' acceptance and commitment to delivering HIV-prevention counselling to their patients during the clinic visit.

Experimental avoidance and high-risk sexual behavior in survivors of child sexual abuse.

While many long-term correlates of child sexual abuse (CSA) have been identified, theories to explain the development of these correlates have received little empirical validation. The process of experiential avoidance is one theory that has been proposed to account for many of the correlates of CSA. The purpose of the current study was twofold: (1) To attempt to develop a more complex measure of experiential avoidance in women with and without a CSA history, and (2) to explore variables related to two of the long-term correlates of CSA, general psychological distress and high risk sexual behavior. Levels of current distress, high-risk sex, and experiential avoidance were examined in 257 undergraduate females (mean age 20.0) using self-report questionnaires. The results of the current study indicate that CSA survivors report higher levels of experiential avoidance and high-risk sexual behavior with persons other than their primary partners. Implications of these findings for theory development, therapy with CSA survivors, and HIV prevention programs are discussed.