| Front | Which of the following hormones is often decreased by approximately 25% in the serum of pregnant women who have a fetus with Down syndrome?A. Estriol (E3)B. Human chorionic gonadotropin (hCG)C. ProgesteroneD. Estradiol (E2) |
| Back | A. Estriol (E3)A E3 is produced in the placenta and fetal liver from dehydroepiandrosterone derived from the mother and fetal liver. E3 is the major estrogen produced during pregnancy, and levels rise throughout gestation. Serum free E3 is often lower than expected for the gestational age in a pregnancy associated with Down syndrome. The combination of low serum free estriol, low-α fetoprotein, high hCG, and highinhibin A is used as a screening test to detect Down syndrome. When one of the four markers is abnormal, amniocentesis should be performed for the diagnosis of Down syndrome by karyotyping or FISH. The four markers have a combined sensitivity (detection rate) of approximately 75%. |
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| Front | The following results are reported on an adult male patient being evaluated for chest pain:Myoglobin Troponin I CK-MB(Cutoff = (Cutoff = (Cutoff =100 µg/L) 0.03 µg/L) 4 µg/L)Admission 12 µg/L 1.1 µg/L 18 µg/L3 hours 360 µg/L 1.8 µg/L 26 µg/Lpostadmission6 hours 300 µg/L 2.4 µg/L 40 µg/LpostadmissionWhat is the most likely cause of these results?A. The wrong sample was assayed for the first myoglobinB. The patient did not suffer an MI until after admissionC. Hemolysis caused interference with the 3-hour and 6-hour myoglobin resultD. The patient is experiencing unstable angina |
| Back | A. The wrong sample was assayed for the first myoglobinA Myoglobin is the first cardiac marker to rise outside the URL following an MI (2-3 hours) followed by TnI (4-6 hours) and CK-MB (4-8 hours). The admission TnI and CK-MB are both elevated, and they continue to rise in all three samples. Because TnI and CK-MB peak before 24 hours post-AMI, the infarction likely occurred within the last 12-24 hours. The myoglobin can remain elevated for up to 36 hours post-AMI and should have been elevated in the admission sample. |
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| Front | Which of the following methods is most useful in order to detect sample misidentification?A. Cumulative summationB. Critical limitC. Delta limitD. Significant change limit |
| Back | C. Delta limitC Cumulative summation is a statistical method used in quality assurance to detect a trend in QC results. Critical limits are used to define when medical intervention is likely needed to prevent injury or death. The significant change limit is the difference in test results that is medically significant, or that which cannot be attributed to the sum of normal physiological and analytical variation. The delta limit (delta check) determines whether the difference between two measurements usually 24-48 hours apart exceeds the expected. Although this can result from an abrupt change in the patient's status, other causes are sample misidentification, contamination, and random error. Delta limits are expressed in percent and vary depending on analyte stability. |
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