The usual criteria of causality, and how they apply to the Ovarian Cancer case-control study (Rosenberg et al.)
According to Hill’s criteria of epidemiological research, if factor A is known to cause B, then A must precede the incidence of B all the time. This is the criterion of temporal relationships. Therefore, in the current case, since the use of combination oral contraceptives (OCs) reduces the occurrence of epithelial ovarian cancer, then the factors that affect the OCs MUST ALWAYS precede the factors affecting the occurrence of ovarian cancer (Rosenberg et al., 1982, p.3210). The next criterion to be considered is Strength which implies that, if the measured association between the two sets of factors is shown to be strong, then the kind of relationship existing between the two is known as causal. According to the results of the current case though not statistically significant, there is a strong correlation between the two sets of factors hence there is a causal relationship. The dose-response relationship criterion posits that, if the dosage is directly proportional to the risk, then this is strong evidence that a causal relationship exists. In the case-control study, it is documented that the risk increases with prolonged use of the Combination OCs, thus a causal relationship does exist in the current case.
Further, the criterion of consistency posits that the causal relationship must be consistent when the results of the current case are replicated using different methodologies and under different circumstances. Since the current results agreed with those of previous studies, the results can be said to be consistent (Rosenberg et al., 1982, p.3212). The criterion of Plausibility also posits that the results of any current study must agree with those documented in previous studies. The current case can be said to be plausible since the association between the two sets of factors agreed with other studies that had been previously documented. According to the criterion of consideration of alternative explanations related to this kind of associations, the researchers in the current case managed to document other causal factors that were perceived to be behind the relationship. Other criteria are also accurately executed in the current case such as the criteria of experiment, specificity and coherence.
The overall purpose of case-control surveillance
The public and the medical communities have been witnessing cases whereby most prescribed drugs are associated with cases of increased risks among the users for many decades. This information is provided by case-control studies on these drugs. With the availability of this information, the responsible individuals can devise ways of ensuring that the drugs prescribed are safe in order to reduce the risks involved (Gurwitz, 2006, p.1414). The results from these studies also provide the clinical significance that can be used to limit the extent of uncertainty and alarm among the general public and other policy makers (Bjerre and LeLorier, 2007, p.505).
Persuasive evidence to suggest that combination oral contraceptives may indeed reduce the risk of ovarian cancer
The study indicates that the results obtained were not statistically significant hence there could be a possibility that the study was biased. Additionally, it is documented that combination oral contraceptives were just one of the numerous options available upon which the same information would have been obtained (Rosenberg et al., 1982, p.3212). Due to these reasons, the study fails to be persuasive enough to guarantee that the use of combination OCs may for sure reduce the risk of ovarian cancer.
Is this study an example of how case-control methods may be used to evaluate multiple outcomes in relation to multiple risks
The current case-control study provides a comparison of the results obtained from the contraceptive users against those of non-contraceptive estrogen users. The former group is shown to experience a reduction in the risk of ovarian cancer while in the latter, the risk increases. This is a clear indication that these studies can be used to evaluate a variety of outcomes related to various risks caused by prescribed medications.
Can confounding be adequately controlled?
By employing experimental controls, it is possible for researchers to adequately control the element of confounding. It has been shown that experimental control can be used to curtail any external influence on the experiment such as the experimenters’ bias, biological factors and environmental variables. This is especially important when carrying out experiments that involve investigating the effect of a single variable on a particular experimental situation.
References
Bjerre, L.M. and LeLorier, J. (2007). Expressing the magnitude of adverse effects in case-control studies: “the number of patients needed to be treated for one Epidemiology and Biostatistics. BMJ; 2000(320): 503-506.
Gurwitz, J.H. (2006). Serious adverse drug effects: seeing the trees through the forest. Massachusetts Medical Society. The New England Journal of medicine; 354(13): 1413-1415.
Rosenberg, L., Shapiro, S., Slone, D., Kaufman, D.W., Helmrich, S.P., Miettinen, O.S., Stolley, P.D., Rosenshein, N.B., Schottenfeld, D., Engle, R.L. (1982). Epithelial ovarian cancer and oral contraceptives. American Medical Association. Journal of the American medical Association; 247(23): 3210-3212.