Introduction to Clinical Laboratory Testing

--- Practice problems ---

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  1. The normal range for fasting serum glucose is 70 - 110 mg/dl. If 1,000 normal people are tested, how many results will be within the normal range?
  2. The mean for a laboratory serum glucose control specimen is 80 mg/dl and the standard deviation is 2.0 mg/dl. What is the 95% confidence interval for the result?
  3. What is the C.V. for the glucose determination in item 2.0 above?
  4. What is the 95% confidence interval for a serum glucose determination reported as 250 mg/dl when the C.V. is 2.0% ?
A new test for diagnosing diabetes mellitus is devised and evaluated from the following:
  • 98 of 100 individuals known to be diabetic tested positive.
  • 198 of 200 individuals known not to be diabetic tested negative.
  1. What is the sensitivity of the test?
  2. What is the specificity of the test?
  3. What is the predictive value of a positive test result when the prevalence of DM is 1%. (repeat for prevalence=0.1% and 10 %)
  4. What is the probability that a negative test result provides an accurate diagnosis?

ANSWERS (first try without looking at the answers)