A scientist in Chicago is studying a new blood test to detect Ab to EBV with increased sensitivity and specificity. So far, her best attempt at creating such an exam reached 82% sensitivity and 88% specificity. She is hoping to increase these numbers by at least 2 percent for each value. After several years of work, she believes that she has actually managed to reach a sensitivity and specificity much greater than what she had originally hoped for. She travels to China to begin testing her newest blood test. She finds 2,000 patients who are willing to participate in her study. Of the 2,000 patients, 1,200 of them are known to be infected with EBV. The scientist tests these 1,200 patients' blood and finds that only 120 of them tested negative with her new exam. Of the patients who are known to be EBV-free, only 20 of them tested positive. Given these results, which of the following correlates with the exam's specificity?
A82%
B90%
C84%
D86%
E98%
A new assay for Lyme disease has been developed. While the assay has been tested extensively in Maine, a group of inventors are planning to test it in Southern California. In comparison to the assay's performance in Maine, testing the assay in Southern California would affect the performance of the assay in which of the following ways?
AGreater likelihood that an individual with a positive test will truly have Lyme disease
BDecreased positive likelihood ratio of the Lyme disease assay
CDecrease negative likelihood ratio of the Lyme disease assay
DLower likelihood that a patient without Lyme disease truly has a negative test
EGreater likelihood that an individual with a negative test will truly not have Lyme disease
A 20-year-old man presents to the emergency department with complaints of severe malaise, fevers, and sore throat for the past 7 days. He also has had episodes of nausea and vomiting during this period. He does not smoke or drink alcohol. There is no family history of liver disease. His blood pressure is 130/80 mm Hg, temperature is 38.3℃ (100.9℉), pulse is 102/min, and respiratory rate is 20/min. On physical examination, he appears ill with bilateral cervical lymphadenopathy. His tonsils are erythematous and enlarged. There is no jaundice and he is mildly dehydrated. Abdominal examination demonstrates splenomegaly. The laboratory findings are shown below: Hemoglobin 15 g/dL Platelet count 95,000/mm³ Leukocytes 13,500/mm³ Neutrophils 50% Atypical lymphocytes 34% AST 232 U/L ALT 312 U/L ALP 120 U/L GGT 35 U/L Total bilirubin 1.2 mg/dL Direct bilirubin 0.2 mg/dL PT 12 seconds The serologic test for hepatitis A, B, and C, CMV, and leptospirosis are negative. Serology for both serum IgM and IgG antibodies for EBV capsid antigen are positive, but the heterophile antibody test is negative. What is the most likely reason for the negative heterophile test?
AConcurrent viral hepatitis A infection
BCMV infection
CLow specificity
DAge of the patient
EFalse negative
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