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The value of LD 50 for a substance is the dose required to kill half the members of a tested population after a specified test duration. LD 50 figures are frequently used as a general indicator of a substance's acute toxicity. A lower LD 50 is indicative of higher toxicity. The term LD 50 is generally attributed to John William Trevan. [2]
The related quantities LD 50 /30 or LD 50 /60 are used to refer to a dose that without treatment will be lethal to 50% of the population within (respectively) 30 or 60 days. These measures are used more commonly with radiation, as survival beyond 60 days usually results in recovery.
A linear no-threshold model is commonly used for illustrating the probability of cancer development from radiation. There is no threshold value at which stochastic health effects start emerging. [25] Only for non-cancer health outcomes, there is an assumption of the presence of a safety margin below which no negative biological effect is ...
Results from large randomized studies have recently prompted a large number of professional organizations and governmental agencies in the U.S. to now recommend lung cancer screening in select populations. The 3 main types of lung cancer screening are low-dose, computerized tomographic (LDCT) screening, chest x-rays, and sputum cytology tests. [4]
The more potent a particular substance is, the steeper this curve will be. In quantitative situations, the Y-axis often is designated by percentages, which refer to the percentage of exposed individuals registering a standard response (which may be death, as in LD 50). Such a curve is referred to as a quantal dose–response curve ...
It is desirous for the value of LD 50 to be as large as possible, to decrease risk of lethal effects and increase the therapeutic window. In the above formula, TI safety increases as the difference between LD 50 and ED 50 increases—hence, a higher safety-based therapeutic index indicates a larger therapeutic window, and vice versa.
This hypothetical screening test (fecal occult blood test) correctly identified two-thirds (66.7%) of patients with colorectal cancer. [ a ] Unfortunately, factoring in prevalence rates reveals that this hypothetical test has a high false positive rate, and it does not reliably identify colorectal cancer in the overall population of ...
Of all women with HSIL results, 2% [8] or less [9] have invasive cervical cancer at that time, however about 20% would progress to having invasive cervical cancer without treatment. [ 10 ] [ needs update ] To combat this progression, HSIL is usually followed by an immediate colposcopy with biopsy to sample or remove the dysplastic tissue.