Learning Objective 3 – Identify the Design of a particularstudy

1) To determine if conversations about HIV status decreases the riskof acquiring HIV among men having sex with me (MSM). From March2008 through May 2010, persons newly diagnosed with HIV-positivemen and HIV-negative men were recruited by researchers. Todistinguish recent (<5 months) from longstanding (>5 months)infection, dried blood spots from people newly diagnosed with HIVwere tested with the BED IgG-capture ELISA. HIV-positive men and the matched HIV-negative men completed a knowledge, attitudes, behavior and practices (KABP)-questionnaire.ResearcherscomparedHIV-positive men with recent infection and matched HIV-negative men amongmen having sex with men (MSM) regarding reported risk behaviorin the previous 6 months.  Whattype of study is this? Explain.Whatare its strengths and limitation?

2) Tumors of the central nervous system are the second most commongroup of childhood cancers in 0-14 year olds (24% of total cancers)and represent a major diagnostic group in 15-24 year olds.Researchers were interested in learning if breastfeeding was aprotective factor in such tumors. Researchers identifiedchildren with a newly diagnosed intracranial tumor. All patients were recruited from one majorclinical cancer treatment center. Children with brain tumors werematched to children without brain tumors that were of similar age,sex, and BMI. These healthy children were drawn from generalpractice lists. What type of study is this? Explain. What are its strengths and limitation?

3) A previous review showed that high stress increases the risk ofoccupational injury by three to five-fold. Researchers examined the effect of stress on recorded hospitalized injuriesover a period of 8 years. A total of 16,385 employees of a loggingcompany responded to the questionnaire. Perceived stress wasmeasured with a validated single-item measure, and analyzed inrelation recorded hospitalized injuries from 1986 to 2008.What type of study is this? Explain. What are its strengths and limitations?