MICROBIO 160 Lecture Notes - Lecture 23: Radiography, Ameloblastoma, Overdiagnosis

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taupegoldfish302

3 Nov 2015

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MICROBIO 160 Full Course Notes

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Lecture 23- cancer screening: cancer"s deadliest weapon is its ability to metastasize. It"s a systematic search for cancer before any symptoms are evident. Why screen: can help find cancer at an early stage, when abnormal tissue/cancer is found early, it may be easier to treat or cure. Pitfalls in using 5-year survival rates to assess screening protocols: lead-time bias- screening may detect a cancer earlier but not affect age of mortality. However, since diagnosis was earlier, 5-year survival rates will be greater and make the screening test appear effective at prolonging life: overdiagnosis bias- screening more likely to detect slow growing tumors that might never cause symptoms or deaths. This inflates 5-year survival rates for a particular screening protocol as well. The ideal screen: would never have false positive results (determine a person has cancer when he or she does not, would never have false negative results (miss the cancer in a person that actually has cancer, doesn"t exist.

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)A screening test is available to identify individuals with a genetic mutation that puts them at greater risk for stroke. The test is extremely expensive and is not covered by most insurance plans, so those choosing to have the test usually have to pay for it out-of-pocket. However, it has been determined that the screening test is very valuable because the annual incidence of stroke among those who have been screened is nearly half that of the general population. 7) One major benefit of mammography screening for breast cancer is that the disease is often diagnosed in the presymptomatic phase of the disease, before it is detectable by any other means, and breast cancers diagnosed in such early stages respond better to treatment. Another benefit of screening is that women diagnosed with breast cancer by way of mammography have better survival rates than women diagnosed by other means. 8) The prognosis for neuroblastoma, a tumor that occurs in young children, varies greatly by patient. Some tumors are slow-growing and may even heal spontaneously. Others tumors are fast-growing and aggressive. A urine screening test for neuroblastoma is currently available that detects metabolites produced by the tumor. It has been suggested that such screening is highly valuable PH20001 Essentials of Epidemiology 2 because the case-fatality rate of neuroblastoma among children diagnosed with the urine test is much lower than it is for those who were not screened. 9) Suppose that a new screening test has recently been developed to aid in the early identification of individuals with rheumatoid arthritis. However, the value of the test has not yet been established. In an effort to test the effectiveness of the new test in predicting a future diagnosis of rheumatoid arthritis, investigators enroll a group of volunteer participants, record their test result, and follow them forward for the development of the condition. It is subsequently determined that the new screening test is highly effective in predicting a definitive diagnosis of rheumatoid arthritis because the incidence of the condition among those who screened positive was much higher than that of the general population. 10) There are at least a dozen types of human papillomaviruses (HPV) that are considered high-risk and cause approximately 5% of all cancers world-wide. However, high-risk HPV infections are common and most occur without any symptoms and resolve on their own within 1-2 years. In 2003, cervical HPV screening tests became available and are now approved for use in combination with a Pap test among women over the age of 30. Such tests can detect infection of several high-risk HPV types before cell changes become evident. Some argue that HPV screening tests should be approved for universal use among women of all ages because the incidence of high-risk HPV infections has increased dramatically over the past decade. Identify the bias being described in the scenario

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MICROBIO 160 Lecture Notes - Lecture 23: Radiography, Ameloblastoma, Overdiagnosis

MICROBIO 160 Full Course Notes

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