Nested study within a cluster randomized controlled trial of three types of financial incentives and no incentives (control).
For the nested study, all charts of black non-Hispanic patients were used from the 40-chart sample, and any additional black non-Hispanic charts were added from the remaining charts in the 70 chart sampling frame.
The nested study was conducted from a cohort of 926 healthy subjects enrolled from the low-income, unplanned settlement in Sultanabad area in eastern Karachi to find out the prevalence of deficiencies of folate, vitamin B6 and vitamin B12.8 For the parent study (February 2006 to March 2007), a sampling frame of 4000 houses was available in this locality of a population of about 53,000 subjects,9 and systematic random sampling was carried out to select houses and subsequently individuals from these houses as described in a previous publication.10
For the nested study (September 2009 to October 2010), 858 healthy adults were included who had no acute or chronic illness, were non-pregnant, and were not taking vitamin D supplements for the preceding 6 months The study was approved by the Ethics Review Committee of the Aga Khan University, Karachi, and informed consent was obtained from all the participants.
Additionally, a nested study
on 34 patients to evaluate the accuracy and feasibility of transmission of echo pictures and heart sounds to Amrita Institute of Medical Sciences, Kochi via satellite using Indian Satellite Research Organization's network was also carried out.
The nested study
population included 248 women who met criteria for preeclampsia and 679 women without preeclampsia who were control subjects.
The GISSI-HF was a nested study
designed to test two hypotheses.
(9) Recently, a nested study
within the Women's Intervention Nutrition Study did show that women with breast cancer who decreased their fat intake to a median of 33 g/day had a hazard ratio of 0.76 for relapse over 60 months (compared with controls who are a median of 51 g/day).
In a nested study
comprising 825 wives of men in the circumcision arm and 783 wives of men in the control arm who were followed for 1 year, the respective rates of symptomatic genitourinary disease in the intervention and control arms were 12.5% and 16.8%.