Question 2
The Health Department conducted a study to assess the validity of a new field test for lead exposure, which they wanted to use for a mass screening program. The field test uses a spot of blood from a finger prick sample which is analyzed using a small hand-held machine.
The results from the field test were compared with the gold standard laboratory test for measuring blood lead concentration in a representative sample of the population identified for the mass screening program.
The results of the study are shown below:
≥15 mg/dL
Gold standard
≥15 mg/dL
Total
≥ 15 mg/dL 135 100 235
≥ 15 mg/dL 15 1400 1415
Total 150 1500 1650
a) Calculate the sensitivity, specificity, positive predictive value and negative predictive
value of the new field test compared with the gold standard test. Interpret the sensitivity
and the positive predictive value.
b) Is this field-test suitable for use as a screening test? Give reasons that support your
answer.
Question 3
Read the edited extract from a published study shown below. Use the information contained in the extract to answer the following questions.
(a) What is the research question?
(b) What type of study has been used? Is it the best study design to answer the research question? Give reasons for your answers.
(c) Describe the source population and the study participants? Were there any issues that could lead to selection bias? Give reasons for your answer.
(d) What were the study factor and primary outcome factor? What did the investigators do to minimize measurement error of the outcome factor? Give reasons for your answers.
(e) What is your assessment of the generalisability of the study findings?
