For which of the following circumstances would you consider initiating chelation, such as with CaEDTA, to treat workers for workplace exposure to lead and other heavy metals?
Answer(s): C
Chelating drugs are given as treatment for symptomatic poisoning by lead and other heavy metals. They should not be given prophylactically, since the agents themselves have some possible toxic side effects.These toxic effects may add to those already caused by ingestion of the metals and may actually increase absorption of the metal. For these reasons, advice should be given to workers to seek employment away from exposure to the offending agent while therapy continues. Removal from exposure is essential if levels are high.
Six hundred asymptomatic men with prostatic nodules are given a PSA test to screen for prostate cancer. With a cutoff of 5 ng/mL, the PSA results are positive in 200 cases. Of these, 100 persons are confirmed on biopsy and follow-up testing to have the disease; however, 50 of the individuals who had negative test results are also shown to have the disease based on biopsy. You have been asked to screen another similar group of 50 men using the PSA test.What proportion of persons having prostatic cancers will you correctly identify in the new group?
Several concepts are important in determining the sensitivity of tests. The percentage sensitivity is the percentage of individuals with the disease (true positives [TP]) detected by the tests. False negatives (FN) are those who have the disease, but who were not detected by the test. The percentage sensitivity is calculated as: TP/(TP + FN) . 100. In the example given in the question, the calculation is 100/(100 + 50) x 100 = 66.7%.
Six hundred asymptomatic men with prostatic nodules are given a PSA test to screen for prostate cancer. With a cutoff of 5 ng/mL, the PSA results are positive in 200 cases. Of these, 100 persons are confirmed on biopsy and follow-up testing to have the disease; however, 50 of the individuals who had negative test results are also shown to have the disease based on biopsy. You have been asked to screen another similar group of 50 men using the PSA test.What proportion of persons with no prostatic cancer will you correctly identify in the new group?
Answer(s): D
The percentage specificity of a test is the percentage of those persons without the disease (true negatives [TN]) who were correctly labeled by the test as not diseased. The false positives (FP) are those who were incorrectly labeled by the test as having the disease. The specificity is thus expressed as TN/(TN + FP) .100. In the example given in the question, the calculation is 350/(350 + 100) x 100 = 77.8%
Several members of a group of young adults camping, cooking, and traveling together in the developing world develop fever, malaise, nausea, and vomiting, and have dark urine. Two have yellow sclera. How could this best have been prevented?
Hepatitis Awas first isolated in 1973. Since then, it has been demonstrated to be conveyed from person to person chiefly by the fecal-oral route. Humans appear to be the only natural host. Outbreaks attributed to food and water supplies are frequently reported. There were an estimated 61,000 new infections in the United States (particularly in the West) in 2003, continuing a trend downward. It does not cause chronic infection. Vaccination is effective and available for persons at risk, including travelers. Examples of where outbreaks occur include: among travelers, among young adults clustered together, and in day care environments.
A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. What is the mean?
The mean, or average, is the total of all readings divided by the number of readings, or (x)/n. In the example described in the question, the total of all readings equals 639; the number of readings is 9.Therefore, the mean is 639 divided by 9, or 71.
Post your Comments and Discuss USMLE STEP2 exam prep with other Community members:
Our website is free, but we have to fight against AI bots and content theft. We're sorry for the inconvenience caused by these security measures. You can access the rest of the STEP2 content, but please register or login to continue.