A 2016 article in JAMA reports the results of a study of treatment outcomes for children with mild gastroenteritis who were given oral rehydration therapy. Enrolled children were randomized to received either rehydration with diluted apple juice (DAJ), or an electrolyte maintenance solution (EMS). As per the study authors:

A 2016 article in JAMA reports the results of a study of treatment outcomes for children with mild gastroenteritis who were given oral rehydration therapy. Enrolled children were randomized to received either rehydration with diluted apple juice (DAJ), or an electrolyte maintenance solution (EMS). As per the study authors:

“The primary outcome was a composite of treatment failure defined by any of the following occurring within 7 days of enrollment: intravenous rehydration, hospitalization, subsequent unscheduled physician encounter, protracted symptoms, crossover, and 3%or more weight loss or significant dehydration at in-person follow-up. Secondary outcomes included intravenous rehydration, hospitalization, and frequency of diarrhea and vomiting.”

Of the 323 children randomized to DAJ, 54 experienced treatment failure. (17 %). Of he 324 children randomized to EMS, 81 experienced treatment failure. (25 %)

1. For this study, what is the outcome of interest?

2. For this study what is the primary exposure of interest?

3. Estimate the risk difference (difference in proportions) of treatment failure for children in the DAJ group compared to children in the EMS group. (DAJ-EMS)

4. Interpret the estimate from item 3 in a sentence.

5. Estimate the relative risk (risk ratio) of treatment failure for children in the DAJ group compared to children in the EMS group.

6. Interpret the estimate from item 5 in a sentence.

7. Estimate the relative odds (odds ratio) of treatment failure for children in the DAJ group compared to children in the EMS group.

8. Interpret the estimate from part f in a sentence.

9. Do the estimated risk difference, relative risk and odds ratio agree in terms of the direction of association?

Question 2

A pilot study was designed to evaluate the potential efficacy of a program designed to reduce prison recidivism amongst inmates who have a documented long-term history of drug and/or alcohol problems. A sample of 11 prisoners was followed for up to 24 months after their most recent release from prison. Six of the inmates returned to prison at 3, 7 9, 11, 14 and 21 months respectively. Five of the inmates had not returned to prison as of the last time they were last contacted which was at 4, 8, 16, 24, and 24 months respectively.

Use the Kaplan Meier approach to estimate the survival curve for this set of inmates

(which tracks the proportion who have not yet returned to prison over time). It will be

helpful to construct a table like the ones appearing in lecture 5: however, all you will

need to report in the quiz generator are certain quantities from this table for specific

times.

10. What is the estimated proportion of the total sample who had not returned to prison by 7 months after enrolling in the study?

11. What is the estimated proportion of the total sample who had not returned to prison by 11 months after enrolling in the study?

12. What is the estimated proportion of persons who did not return to prison at 11 months among those who were still at risk of returning to prison at 11 months?

13. What is the estimated percentage of the original sample had not return to prison by 16 months?

14. Why does the Kaplan-Meier curve not reach 0% by the end of the follow-up period?

Question 3

In a July, 2010 article published in the New England Journal of Medicine[footnoteRef:1], researchers report the results of a randomized clinical trial to evaluate mortality differences in HIV infected subjects in Haiti. Subjects were randomized to receive early versus the current standards for implementation of Antiretriviral therapy. [1: Sever P, et al. Early versus Standard Antiretroviral Therapy for HIV-Infected Adults in Haiti. New England Journal of Medicine. (2010). Vol 363, No 3. ]

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