Observational studies cohort

Epidemiological studies. Epidemiology is the study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems. Therefore, epidemiological studies harvest valid and precise information about the causes, prevention and treatments for disease. Types of epidemiological studies are experimental studies and observational studies (cohort and case-control studies). Homocysteine. Homocysteine is a sulfur-containing amino acid that occurs naturally in all humans. Elevated plasma homocysteine concentration is linked to an increased risk of ischemic stroke. Lowering homocysteine plasma levels is linked to increasing the intake of folic acid and vitamins Bg and Bi2-... 

Zschabitz S, Cheng TY, Neuhouser ML, Zheng Y, Ray RM, MiUer JW, et al. B vitamin intakes and incidence of colorectal cancer results from the Women s Health Initiative Observational Study cohort. Am J CHn Nutr February 2013 97(2) 332. ... 

To compare the epidemiological, clinical, and economic impacts of the HIV epidemic in Italy prior to and after the introduction of HAART, Tramarin et al. (2004) conducted a prospective and observational study with a multi-center design. They used data collected on an AIDS cohort from 1994 and updated data from a comparable cohort in 1998. Mortality and medical costs of 251 patients were measured in 1994 and in 1998, respectively. A considerable difference was observed in mortality (33.9% in 1994 vs. 3.9% in 1998). The cost per patient per year was US 15,515 in 1994 and US 10,312 in 1998. Based on the comparison of the two cohorts between both years, the authors concluded that after the introduction of HAART, hospital-based provision shifted from an inpatient-based to an outpatient-based service, with major focus on pharmaceutical care. 

In this context, a decision on whether postmarketing surveillance studies should be built into the development programme must be taken. Such an observational study may signal the occurrence of adverse events or alternatively it may signal and quantify the frequency of adverse events. At this point in the life cycle of a new medicine, post-marketing surveillance is likely to involve cohort observational studies of 10-20 000 patients. The value of these studies is likely to be three-fold ... 

A total of 60 eligible papers were identified 22 were observational studies of patients receiving specific treatment 32 were observational studies, not based on specific treatments 6 were randomized controlled trials. No studies adhered to all six methodological principles. When the principles were relaxed to include only an inception cohort with adequate reporting and analysis of censored patients and appropriate endpoints, only two reports met these criteria, both from the Oxfordshire Community Stroke Project (OCSP 184 patients, follow-up over 3.7 years) (Dennis et al. 1989, 1990). 

Observational studies Case-control Cross-sectional Cohort... 

Observational studies, where the drug is observed epidemiologically under conditions of normal use in the community, i.e. pharmacoepidemiology. Techniques used for postmarketing (Phase 4) studies include the observational cohort study and the case-control study. The systems are described on page 69. 

A meta-analysis has helped to clarify this issue (96). The aim was to assess the presence and magnitude of any possible interaction in peptic ulcer disease between these two susceptibility factors, with particular attention to bleeding peptic ulcer disease, the sites of ulceration, and the effect of H. pylori eradication. In all, 61 relevant studies were identified, 36 of which were excluded for various reasons. Thus, 25 studies were left for analysis, of which 16 observational studies (eight cross-sectional studies, seven case-control studies, and one cohort study) provided data on the prevalence of peptic ulcer disease in 1633 NSAID users, with data on H. pylori status for 1625 patients. The pooled frequency of peptic ulcer disease in NSAID users was 42% in those who were H. py/on-positive and 25% in those who were H. py/on-negative (OR = 2.12 95% Cl = 1.68, 2.67). 

Three observational studies using national cohorts have examimed the risk of deteriorating renal function with chronic NSAID exposure. Two of the reports in-volvedata from the Physician Health Study [99A, 99B] while the third involved the nurses from the National Health Survey [99C]. After adjusting for confounding risk factors none of the studies identified an increase risk of loss of renal function with moderate NSAID intake. More recently Ibanez et al [99D] conducted a 2 year case control study regarding the relative risk of ESRD associated with NSAIDs. They reported a Odd Ratio of 1.22 (CL 0.89-1.66) for the risk of ESRD associated with NSAIDs. 

H urst FP, Bohen EM, Osgard EM, Oliver DK, Das NP, Gao SW, Abbott KC. Acute kidney injury associated with oral sodium phosphate purgative use An observational retrospective cohort study. J Am Soc Nephrol. 2007 18 3192-8. 

The overall study cohort was broken down into sub-groups based upon maternal hair mercury concentration as follows 3 ppm (n=164), 4-6 ppm (n=215), 7-9 ppm (n=161), 10-12 ppm (n=97), and >12 ppm (n=99). No significant or remarkable effect on the activity of the respective groups of children was observed outside the highest concentration group (i.e., maternal hair concentrations >12 ppm). 

Despite the deserved enthusiasm for the contribution of the LAMPS to epidemiology, more traditional hands-on, structured observational studies, with enrollment of cohorts of persons exposed to an agent under study and proper comparator populations, and selection of cases (e.g. from medical records) and appropriate controls, still have specific applications in pharmaceutical medicine, thus characterizing part of the activity of pharmacoepidemiologists. 

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