A Program to Calculate Sample Size, Power, and Least Detectable Relative Risk Using a Programmable Calculator

The power of the association between oral contraceptives and breast cancer was analysed in all the papers published up to date. Seventy-seven publications (from 44 studies) were collected and graded as to quality using meta-analytical methods. Power achieved a figure of greater than or equal to 0.8 in a 10.8% of the associations studied. It showed a significant relationship with the existence of a significant relative risk of the oral contraceptives for breast cancer. The relationship with the sample size of a study was not linear. Power did not show any significant relationship to other variables related to the design of a study (apart from matching, being the power higher in unmatched studies), or to the biases detected, although studies considered as unbiased yielded a higher power. Logistic regression analysis included as predictors of a power greater than or equal to 0.80 the existence of a significant relative risk and the lack of biases in a research.

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Comparison of the Cancer Risk of Methylene Chloride Predicted from Animal Bioassay Data with the Epidemiologic Evidence

Tollefson¹,

Lorentzen²,

Brown³

et al. 1990

Risk Analysis

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Methylene chloride has been shown to be a lung and liver carcinogen in the mouse; yet, the current epidemiologic data show no adverse health effects associated with chronic exposure to this compound. Hearne et al. have compared the results of a large mortality study on occupational exposure to methylene chloride to the human risk predictions based on the rodent bioassay to point out the inconsistency between the animal toxicologic and human epidemiologic data. The maximum number of lung and liver cancers predicted due to methylene chloride exposure based on the rodent bioassay data was 24 compared to 14 deaths from these cancers actually observed in the Hearne et al. epidemiology study. We assess the minimum risk detectable by the human study in order to calculate the upperbound potency of methylene chloride and compare it to the potency derived from the bioassay data. Results from the epidemiology study imply an upperbound potency of 1.5 x 10(-2) per ppm, compared to 1.4 x 10(-2) per ppm calculated using the most conservative analysis of the animal data. We conclude that the negative epidemiology study of Hearne et al. is not sufficiently powerful to show that the risk is inconsistent with the human risk estimated by modeling the rodent bioassay data. Specifically, the doses to which the workers were exposed, the population studied, and the latency period were not adequate to determine that the risks are outside the bounds of the risk estimates predicted by low-dose modeling of the animal data.

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A Program to Calculate Sample Size, Power, and Least Detectable Relative Risk Using a Programmable Calculator

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Understanding and evaluating clinical trials

Understanding and evaluating clinical trials

Anticonceptivos Orales y Cáncer de Mama: Análisis de la Potencia Estadística de la Asociación

Comparison of the Cancer Risk of Methylene Chloride Predicted from Animal Bioassay Data with the Epidemiologic Evidence

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