Combining censored and uncensored data in a U-statistic: design and sample size implications for cell therapy research.

The assumptions that anchor large clinical trials are rooted in smaller, Phase II studies. In addition to specifying the target population, intervention delivery, and patient follow-up duration, physician-scientists who design these Phase II studies must select the appropriate response variables (endpoints). However, endpoint measures can be problematic. If the endpoint assesses the change in a continuous measure over time, then the occurrence of an intervening significant clinical event (SCE), such as death, can preclude the follow-up measurement. Finally, the ideal continuous endpoint measurement may be contraindicated in a fraction of the study patients, a change that requires a less precise substitution in this subset of participants.A score function that is based on the U-statistic can address these issues of 1) intercurrent SCE's and 2) response variable ascertainments that use different measurements of different precision. The scoring statistic is easy to apply, clinically relevant, and provides flexibility for the investigators' prospective design decisions. Sample size and power formulations for this statistic are provided as functions of clinical event rates and effect size estimates that are easy for investigators to identify and discuss. Examples are provided from current cardiovascular cell therapy research.

Greater adherence to highly active antiretroviral therapy (HAART) between pregnant versus non-pregnant women living with HIV.

One of the most remarkable advances in the control of the HIV/AIDS pandemic has been the introduction of highly active antiretroviral therapy (HAART). The use of HAART has been associated to reductions in AIDS-related mortality in most countries where HAART is available. Unfortunately, the adherence required to keep good control of viral replication is higher than what is required in other medical conditions. Several studies have shown a relationship between adherence and viral suppression ranging between 90-95% required for complete suppression. Multiple factors have been related to adherence among which are: gender, racial/ethnic distribution, age, personality traits, education, alcohol use and others. For women living with HIV there might be additional difficulties to handle in order to be adherent (i.e. multiple family responsibilities). A group of 165 women living with HIV attending a multidisciplinary clinic were interviewed with a 3-day adherence questionnaire. Correlation with clinical information was obtained from the Clinic Data Base. A total of 37 pregnant and 128 non-pregnant women were included in this analysis, 96% of which were on HAART. Complete adherence (100%) was reported by 91% of the pregnant and 70% of the non-pregnant women. (Fisher's exact test 0.009). The majority, 99% knew the names of their medications. There were no differences among groups in scholarity, history or actual cigarette smoking, history or actual drug use, CD4 lymphocyte counts (median or proportion below 350 cells/mm3), mean HIV RNA viral load or the proportion of patients with HIV RNA < 1,000 copies/ml. The transmission rate for the sample of pregnant women was zero. The reported adherence rates to HAART for women living with HIV were highest among the pregnant women. This difference was statistically significant (Chi Sq 0.05). The great majority (93%) reported knowing the names of the medications. In spite of reported barriers to adherence, pregnant women attending a multidisciplinary clinic for HIV care and research, reported good rates of adherence to HAART. This is also reflected in the good perinatal outcomes. Non-pregnant women with lower adherence rates might need additional interventions to improve adherence.